Articles

Articles are a collaborative effort to provide a single canonical page on all topics relevant to the practice of radiology. As such, articles are written and edited by countless contributing members over a period of time. A global group of dedicated editors oversee accuracy, consulting with expert advisers, and constantly reviewing additions.

755 results found
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Lung cancer

Lung cancer (primary lung cancer), or frequently if somewhat incorrectly known as bronchogenic carcinoma, is a broad term referring to the main histological subtypes of primary lung malignancies that are mainly linked with inhaled carcinogens, with cigarette smoke being a key culprit.  This art...
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Lung carcinomas of the salivary gland type

Lung carcinomas of the salivary gland type are also known as salivary gland–type tumors of the lung (SGTTLs) or bronchial gland neoplasms.  The usual consignation to the group of non-small cell lung cancer (NSCLC) may be unfortunate because the clinical behavior of SGTTLs can be quite different...
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Lung surgery

Lung (or pulmonary) surgery is most frequently performed for lung carcinoma, and encompasses a broad spectrum of procedures: sublobar resections wedge resection segmentectomy lobectomy: commonest surgery for bronchogenic carcinoma includes sleeve lobectomy and bilobectomy pneumonectomy Te...
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Lymphangitic carcinomatosis

Lymphangitic carcinomatosis, or lymphangitis carcinomatosa, is the term given to tumor spread through the lymphatics of the lung and is most commonly seen secondary to adenocarcinoma. Epidemiology The demographics will reflect that of the underlying malignancy (see below). Clinical presentati...
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Lymph node enlargement

Lymph node enlargement (rarely lymphadenomegaly) is often used synonymously with lymphadenopathy, which is not strictly correct. Terminology Lymphadenopathy (or adenopathy) is, if anything, a broader term, referring to any pathology of lymph nodes, not necessarily resulting in increased size; ...
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Lymphedema

Lymphedema is the pathologic accumulation of fluid in the soft tissues as the result of impaired lymphatic drainage, with resultant inflammation, adipose tissue hypertrophy, and fibrosis. It can be either primary or secondary, due to surgery or disease processes. The condition can cause disfigur...
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Lymphoma

Lymphoma (historically lymphosarcoma was used for diffuse forms of the disease) is a malignancy arising from lymphocytes or lymphoblasts. Lymphoma can be restricted to the lymphatic system or can arise as extranodal disease. This, along with variable aggressiveness results in a diverse imaging a...
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Lymphoma of the spinal cord

Lymphoma of the spinal cord is an uncommon manifestation of lymphoma. Although lymphoma more commonly involves the vertebral body (vertebral body tumors) or epidural compartment, intramedullary lymphoma may rarely occur.   Apparent intramedullary spinal cord lymphoma may often, in fact, represe...
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Lymphoma of the uterine cervix

Lymphoma of the uterine cervix is generally uncommon and when it does occur tends to present as cervical involvement with added background multi-organ disease rather than isolated primary cervical lymphoma 1. It is often considered part of the spectrum of uterine lymphoma. Epidemiology In the ...
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Lymphoma (staging)

Many lymphoma staging systems for both Hodgkin lymphoma and non-Hodgkin lymphoma have been developed. The most widely used currently is the Lugano staging classification, which also separately defines criteria for response to treatment assessed by PET-CT or by CT alone. Patients having undergon...
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Lymphomatoid granulomatosis (CNS manifestations)

Lymphomatoid granulomatosis of the central nervous system is uncommon, but represents the second most common site of involvement in patients with systemic lymphomatoid granulomatosis, after the lungs, which are most commonly involved. It is considered one of the immunodeficiency-associated CNS l...
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Lymphoscintigraphy

Lymphoscintigraphy is a nuclear medicine technique to visualize regional lymphatic drainage, especially for mapping sentinel lymph nodes, from a site of radiopharmaceutical injection. Radiopharmaceutical Colloidal agents are used as these particles enter lymphatic channels and migrate to lymph...
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Magnetic resonance lymphangiography

Magnetic resonance lymphangiography (MRL) is an imaging technique used to visualize and map the lymphatic vessels. The technique is used for treatment planning in supermicrosurgical procedures, including lymphaticovenous anastomosis, lymphaticolymphatic bypass and vascularized lymph node transfe...
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Male breast cancer

Male breast cancer is exceptionally rare and only accounts for less than 0.25% of male malignancies and ~0.5-1% of all breast cancer (both genders). The diagnosis is sometimes delayed due to the patient's hesitancy to seek advice. Workup from a radiological point of view is the same as for women...
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Male breast disease

Male breast disease includes a wide spectrum of conditions. Many conditions and entities that affect the female breast may also affect the male breast.  Pathology Malignant male breast cancer lymphoma dermatofibrosarcoma Benign gynecomastia pseudogynecomastia: fat deposition within the b...
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Malignant biliary tract obstruction (summary)

This is a basic article for medical students and other non-radiologists Malignant biliary tract obstruction (MBTO) represents a group of conditions that cause obstructive jaundice. While most examples are the result of pancreatic head cancers, other malignancies may be causative. Reference art...
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Malignant fibrous histiocytoma

Malignant fibrous histiocytoma (MFH), which has more recently been classified as pleomorphic undifferentiated sarcoma (PUS) and formerly known as fibrosarcoma, is considered the most common type of soft tissue sarcoma. It has an aggressive biological behavior and a poor prognosis. As in the maj...
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Malignant melanoma

Malignant melanoma is a malignant neoplasm that arises from melanocytes (or cells that derive from melanocytes).   Pathology Melanocytes predominantly occur in the basal layer of the epidermis and most melanomas, therefore, arise in the skin.  However, melanocytes do occur in other locations a...
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Malignant peritoneal mesothelioma

Malignant peritoneal mesothelioma is an uncommon primary tumor of the peritoneal lining. It shares epidemiological and pathological features with - but is less common than - its pleural counterpart, which is described in detail in the general article on mesothelioma. Other abdominal subtypes (al...
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Malignant pleural disease

Malignant pleural disease usually heralds a poor prognosis, whether it represents a primary pleural malignancy or metastatic involvement.  Clinical presentation Clinical presentation is variable. Patients may be asymptomatic or have pleuritic pain. If associated with a sizeable pleural effusio...
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Malignant pleural mesothelioma (staging)

A number of staging systems have been described for staging of malignant pleural mesothelioma. Below is the International Mesothelioma Interest Group TNM staging system. TNM T - Tumor Tx: primary tumor cannot be assessed T0: no evidence of primary tumor T1a potentially resectable only par...
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Malignant transformation

Malignant transformation is the term given to the process whereby either normal, metaplastic, or benign neoplastic tissue, becomes a cancer. The process usually occurs in a series of steps and the affected tissue gradually accumulates the genetic mutations that express a malignant phenotype. The...
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MALT lymphoma

Mucosa-associated lymphoid tissue (MALT) lymphoma, also called extranodal marginal zone B-cell lymphoma, is a type of low-grade extranodal lymphoma.  Epidemiology MALT lymphoma represents ~7.5% of non-Hodgkin lymphomas. The average age of presentation is 60 years with a slight female predomina...
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Mammalian target of rapamycin

The mammalian target of rapamycin (mTOR), also known as mechanistic target of rapamycin, are two proteins that are involved in cell signaling pathways implicated in tumorigenesis. The mTOR proteins are serine/threonine protein kinases that combine with several other proteins to form two large c...
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Mandibular lesions

Mandibular lesions are myriad and common. The presence of teeth results in lesions that are specific to the mandible (and maxilla) and a useful classification that defines them as odontogenic or non-odontogenic. While it may often not be possible to make a diagnosis on imaging alone, this classi...
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Mantle cell lymphoma

Mantle cell lymphoma (MCL) is a type of non-Hodgkin lymphoma (NHL) and accounts for ~5% of all NHL. It is a malignant neoplasm of virgin B cells that closely resemble normal mantle zone B cells surrounding germinal centers. Epidemiology They occur in older adults (mean age ~60 years). There is...
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Masaoka staging system of thymoma

The Masaoka staging system is commonly adopted for thymomas 1-3, and is the most important determinant of survival following surgical resection 4: stage I: intact thymic capsule stage II: capsular invasion into adjacent mediastinal fat or pleura stage III: macroscopic invasion into adjacent o...
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Maxillary antral carcinoma

Maxillary antral carcinomas are an uncommon head and neck malignancy. They usually present late despite growing large since they remain confined to the maxillary sinus and produce no symptoms. Epidemiology Most commonly affects patients over 45 and has a strong male predilection (M:F = 5:1). M...
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Mediastinal lymph node enlargement

Mediastinal lymph node enlargement can occur from a wide range of pathologies. It may occur on its own or in association with other lung pathology. Terminology Although mediastinal lymphadenopathy is used interchangeably - by some - with "mediastinal lymph node enlargement", they are not synon...
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Medullary thyroid cancer (staging)

Medullary thyroid cancer staging refers to TNM staging of medullary thyroid carcinomas. Papillary, follicular, and anaplastic thyroid carcinomas have similar TNM category definitions but different prognostic stage group definitions. The following article reflects the 8th edition manual published...
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Medulloblastoma

Medulloblastomas are the most common malignant brain tumor of childhood. They most commonly present as midline masses in the roof of the 4th ventricle with associated mass effect and hydrocephalus. Treatment typically consists of surgical resection, radiation therapy, and chemotherapy, with the ...
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Meningeal hemangiopericytoma

Meningeal hemangiopericytomas are rare tumors of the meninges, now considered to be aggressive versions of solitary fibrous tumors of the dura, often presenting as a large and locally aggressive dural mass, frequently extending through the skull vault. They are difficult to distinguish on imagin...
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Meningeal melanocytoma

Meningeal melanocytomas are rare benign primary melanocytic tumors of the CNS that are derived from leptomeningeal melanocytes. They can occur anywhere along the neuraxis but are most commonly found in the spinal canal near the foramen magnum, as well as the posterior cranial fossa, Meckel cave,...
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Meningeal melanomatosis

Meningeal melanomatosis is an aggressive version of meningeal melanocytosis and one of the recognized primary melanocytic tumors of the CNS. It represents proliferation of melanocytic cells within the subarachnoid space 1. There is a strong association with cutaneous melanocytic lesions, in whic...
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Meningioma

Meningiomas are extra-axial tumors and represent the most common tumor of the meninges. They are a non-glial neoplasm that originates from the meningocytes or arachnoid cap cells of the meninges and are located anywhere that meninges are found, and in some places where only rest cells are presum...
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Mesothelioma

Mesothelioma, also known as malignant mesothelioma, is an aggressive malignant tumor of the mesothelium. Most tumors arise from the pleura, and so this article will focus on pleural mesothelioma. Given the presence of the mesothelium in different parts of the body, mesothelioma can arise in var...
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Mesothelioma (summary)

This is a basic article for medical students and other non-radiologists. Pleural mesotheliomas are malignant tumors of the lining of the lungs. There is a strong association with asbestos exposure. Reference article This is a summary article; read more in our article on mesothelioma. Summary...
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Metastases to testis

Metastases to testis are a very rare cause of a testicular mass and may be bilateral in up to 15% of patients.  Epidemiology Metastases to the testes are apparent in ~0.04% of autopsy studies in patients with known malignancy. The average age is 57 years, much older than the primary age for pr...
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Metastases to the breast

Metastases to the breast from non-mammary primary tumors are uncommon and account for 0.5-2.0% of all breast malignancies.  Clinical presentation Metastases do not tend to cause retraction of the skin or nipple. Metastatic lesions are much more likely to be multiple or bilateral than primary c...
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Metastases to the ovary

Metastases to the ovary are relatively common with a documented incidence of 5-30% of all malignant ovarian masses. These may be incorrectly grouped under Krukenberg tumors, which are signet cell containing tumors that form only 30-40% of all ovarian metastases.   Clinical presentation There ...
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Metastases to the thymus

Metastases to the thymus are rare, although they are probably under reported due to lack of symptoms.  Pathology Varied primary tumors have been reported to metastasize to the thymus 1,2: breast cancer lung cancer ovarian cancer colorectal carcinoma gastric cancer prostate cancer testic...
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Metastases to the thyroid

Metastases to the thyroid are an uncommon cause of thyroid malignancy.  Epidemiology Metastases to the thyroid represent 1.4-3% of all malignancies 5. In autopsy series, the incidence is ~10% (range 2-24%) 1,5.  Pathology The most common sites of primary malignancy include (note these will v...
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Metastases to the uterus

Metastases to the uterus is a rare occurrence accounting for less than 10% of all cases of metastases to the female genital tract from extragenital cancers 3. The endometrium is reported to be even less frequently affected by metastases.  Uterine metastases however can occur from a number of si...
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Metastases to the vagina

Metastases to the vagina are more common than primary vaginal malignancies and account for >80% of vaginal tumors. Pathology Metastases usually spread from contiguous sites most commonly, with lymphatic and hematogenous metastases also recognized. Tumors that metastasize to the vagina include...
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Metastatic melanoma

Metastatic melanoma is known for its aggressive nature and for its ability to metastasize to a variety of atypical locations, which is why it demonstrates poor prognostic characteristics. Epidemiology Melanoma accounts for ~5% of all skin cancers, however, it remains the leading cause of death...
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Metastatic pulmonary calcification

Metastatic pulmonary calcification (MPC) is a form of pulmonary calcification where there is calcium deposition in normal lung parenchyma. It is most commonly due to chronic renal failure.  Terminology Metastatic pulmonary calcification is an unfortunate term in that "metastatic" suggests a ma...
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Microinvasive carcinoma of the breast

Microinvasive carcinoma is a type of epithelial breast cancer in which microscopic foci of tumor cells infiltrate the breast stroma. Pathology Microinvasive carcinoma is defined histologically as one or more clearly separate foci of tumor cells ≤1 mm in size infiltrating the mammary stroma 1. ...
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Micrometastasis

Micrometastases are defined by the UICC TNM Classification of Malignant Tumors as conglomerations of tumor cells measuring between 0.2 mm and 2 mm in size. Clusters of cells sized less than 0.2 mm in maximal dimension are termed isolated tumor cells (ITCs). Tumor clusters measuring larger than 2...
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Minor salivary gland tumors

Minor salivary gland tumors are a subtype of salivary gland tumors originating from the minor salivary glands, which are found in the lips, tongue, hard palate, and the mucosa of the oropharynx and larynx, among other locations. Epidemiology MSGTs account for ~15% of all salivary gland tumors....
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Monoclonal gammopathy of undetermined significance

Monoclonal gammopathy of undetermined significance (MGUS) is the most common plasma cell disorder and refers to the presence of an abnormal monoclonal antibody in the blood but the absence of the overt bone marrow and clinical signs of multiple myeloma. Epidemiology MGUS is the most common pla...
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MRI protocols

MRI protocols are a combination of various MRI sequences, designed to optimally assess a particular region of the body and/or pathological process. There are some general principles of protocol design for each area. However, the specifics of a protocol are dependent on MRI hardware and software...
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MRI reporting guidelines for cervical cancer

MRI reporting guidelines for cervical cancer help maintain uniformity of reports and assessment of important imaging staging criteria. Tumor size The tumor should be measured in three orthogonal planes. Tumors with a maximum diameter >4 cm are usually not amenable to primary radical surgery. ...
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MRI targeted prostate biopsy

MRI targeted prostate biopsy refers to an imaging targeted technique rather than the traditional systematic approach of a prostate biopsy after respective imaging with multiparametric MRI (mpMRI) of the prostate. As a consequence of the recent advances of multiparametric MRI (mpMRI) of the pros...
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Mucinous carcinoma of the cervix

Mucinous carcinoma of the cervix is an uncommon histological subtype of cervical cancer. It falls under the group of adenocarcinoma of the cervix. Radiographic features MRI As a general rule any mucin-producing tumor will produce very high T2 signal 1. An enhancing lesion, irregular margin, ...
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Mucosal melanoma

Mucosal melanomas are non-cutaneous malignant melanomas arising from mucosal epithelium. This article is an overview; for specific locations in the body, see their respective articles: sinonasal mucosal melanoma. Epidemiology Mucosal melanomas are rare, comprising about 1% of all melanomas 1....
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Mucosal melanoma of the head and neck (staging)

Mucosal melanoma of the head and neck staging refers to TNM staging of mucosal melanoma involving the nasal cavity, paranasal sinuses, oral cavity, and, less commonly, pharynx and larynx. The system is distinct from staging of carcinomas of those sites and of cutaneous melanoma. The following ar...
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Multiparametric MRI (mpMRI) of the prostate

Multiparametric MRI (mpMRI) of the prostate combines anatomic information from T1-weighted and T2-weighted sequences with functional information from diffusion-weighted imaging (DWI) and dynamic contrast enhancement (DCE). In some situations other techniques like MR spectroscopy (MRS) may also b...
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Multiple cystic neck lesions (differential)

The differential diagnosis for multiple cystic neck lesions is different to that for a solitary cystic neck mass. Differential diagnosis Cystic neck lesions are seen in: metastatic squamous cell carcinoma: older patient, M>F metastatic papillary thyroid carcinoma: usually a younger patient, ...
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Multiple myeloma

Multiple myeloma is a monoclonal gammopathy and is the most common primary malignant bone neoplasm in adults. It arises from red marrow due to the monoclonal proliferation of plasma cells and manifests in a wide range of radiographic abnormalities. Multiple myeloma remains incurable. Terminolog...
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Multiple myeloma (extraosseous manifestations)

Extraosseous myeloma refers to any manifestation of multiple myeloma where there is plasma cell proliferation outside the skeletal system. This can potentially affect any organ system and the reported disease spectrum includes: reticuloendothelial system lymph nodes (considered to be most comm...
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Muscle lymphoma

Muscle lymphoma is a rare manifestation of lymphoma. Epidemiology Muscle lymphoma is rare, representing <2% of all lymphomas. The average age of presentation is 70 years 1. Clinical presentation Focal swelling and/or pain along with B-type symptoms 2. Any muscle can be involved but most comm...
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Musculoskeletal angiosarcoma

Musculoskeletal angiosarcomas, (along with hemangiopericytomas and hemangioendotheliomas) are tumors that arise from vascular structures. They are typically difficult to distinguish from one another on imaging alone. Angiosarcomas, are the most aggressive of the three, frequently having metasta...
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Mycosis fungoides

Mycosis fungoides (MF), also known as cutaneous T-cell lymphoma, is a type of malignant T-cell lymphoma that primarily involves the skin.  Epidemiology In the United States, it is more common in males and African Americans. In Europe, it accounts for ~6% of all non-Hodgkin lymphomas. It is rar...
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Myelodysplastic syndrome

Myelodysplastic syndromes (MDS) are a heterogeneous group of clonal hematological stem cell disorders characterized by dysplasia and ineffective hematopoiesis. It carries a risk of transformation to acute leukemia. Epidemiology Its overall incidence is thought to be around 3.3 per 100,000. The...
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Myeloid sarcoma

Myeloid sarcomas, also called granulocytic sarcomas, chloromas, or extramedullary myeloid tumors, are rare extramedullary masses comprised of myeloid precursor cells. Most commonly, these tumors happen in association with acute myeloid leukemia (AML), but they may also occur with other myeloprol...
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Myeloproliferative neoplasm

Myeloproliferative neoplasms are a diverse group of conditions that are characterized by an excess of terminally differentiated myeloid cells (red cells, white cells, and/or platelets) in the peripheral blood. Pathology Classification The classic four types of myeloproliferative neoplasms are...
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Myo-inositol peak

Myo-inositol is one of the compounds images with MR spectroscopy (MRS) at both 1.5 T and 3 T and is seen to resonate at 3.5 ppm chemical shift (right of the choline peak).  Myo-inositol is a precursor of both phosphatidylinositol (the major inositol-containing phospholipid) and of phosphatidyli...
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Myxofibrosarcoma

Myxofibrosarcoma is a malignant soft tissue tumor. It is classified as a type of a fibroblastic/myofibroblastic tumor. Terminology Previously known as a myxoid variant of malignant fibrous histiocytoma 7. Epidemiology Typically presents in older patients (6th decade) 3. There may be male pre...
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Nasopharyngeal carcinoma

Nasopharyngeal carcinomas (NPC) are the most common primary malignancy of the nasopharynx. It is of squamous cell origin, some types of which are strongly associated with the Epstein-Barr virus (EBV). Epidemiology Nasopharyngeal carcinoma accounts for ~70% of all primary malignancies of the na...
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Necrobiotic xanthogranuloma

Necrobiotic xanthogranulomas are a rare form of cutaneous non-Langerhans cell histiocytosis. Epidemiology The condition occurs mostly in older adults 2. Clinical presentation Patients demonstrate cutaneous papules that develop into large, firm plaques, papules and nodules, which are often ye...
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Neonatal neuroblastoma

Neonatal neuroblastoma is a type of congenital neuroblastoma, an embryonal tumor arising from the sympathetic nervous system. In the majority of cases (45%), the tumor is localized in the adrenal gland.  Epidemiology Neonatal neuroblastoma accounts for less than 5% of all cases and carries a f...
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Neoplasms of the spinal canal

Neoplasms of the spinal canal encompass a range of tumors which arise from or involve the spinal cord, theca, and spinal nerves. Pathology These can be divided according to the tissue/structure of origin within the spinal canal. Tumors of vertebral bodies are discussed separately: see vertebra...
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Nephroblastomatosis

Nephroblastomatosis refers to diffuse or multifocal involvement of the kidneys with nephrogenic rests (persistent metanephric blastema). Epidemiology Nephrogenic rests are found incidentally in 1% of infants. Pathology Nephrogenic rests are foci of metanephric blastema that persist beyond 36...
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Neuroblastoma

Neuroblastomas are tumors of neuroblastic origin. Although they may occur anywhere along the sympathetic chain, the vast majority arise from the adrenal gland. They represent the most common extracranial solid childhood malignancy and are the third commonest childhood tumor after leukemia and b...
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Neuroblastoma (image-defined risk factors)

Image-defined risk factors are imaging features seen at the time of neuroblastoma diagnosis that confer a poorer prognosis. The International Neuroblastoma Risk Group (INRG) suggested an update (2009) to the neuroblastoma staging with a list of features that, if present, upstages a patient with ...
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Neuroblastoma (staging)

There are two methods of neuroblastoma staging, one that is based on post-operative patients (INSS) and one developed for pre-treatment patients (INRGSS). Staging International Neuroblastoma Staging System (INSS) This staging system is for post-operative patients and mainly for prognosis 1: ...
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Neuroendocrine tumors

Neuroendocrine tumors (NETs) represent a wide spectrum of disease. They consist of a large heterogeneous group of malignancies that are derived from embryonic neural crest tissue found in various organ such as the hypothalamus, pituitary gland, thyroid gland, adrenal medulla, and gastrointestina...
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Neutron therapy

Neutron therapy is a form of particle therapy using neutrons as the energy-carrying particle. The therapy has shown promise for some malignancies but there have also been problems with accurate dose distributions and late complications. Some of these problems historically were thought to be - at...
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Nonbacterial thrombotic endocarditis

Nonbacterial thrombotic endocarditis (NBTE), also referred as marantic endocarditis, refers to fibrin and platelets aggregations on previously undamaged heart valves, in patients without bacteremia. The condition is seen in patients with advanced stage malignancies and is related to episodes of ...
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Non-seminomatous germ cell tumors

Non-seminomatous germ cell tumors (NSGCT) are one of the main groups of germ cell tumors (the other being seminoma). Although they are made up of distinct histological entities, in general, they have similar radiographic appearances. They can, however, be found widely in the body, with variable ...
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Non-small-cell lung cancer

Non-small-cell lung cancer represents a heterogeneous group of lung cancers that do not have "small cells" on histology. They are thus separated, as small cell carcinoma of the lung has distinctive management implications. The major histological types include: adenocarcinoma of lung squamous c...
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Ocular pathology

Ocular pathology covers a wide range of conditions and therefore represents the cause of a wide range of symptoms, signs and radiographic features. Ocular metastases account for over 80% of all ocular pathology. With regard to the remainder of ocular lesions, the primary differentiating factor ...
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Esophageal cancer (summary)

This is a basic article for medical students and other non-radiologists Esophageal cancer is a relatively uncommon tumor that occurs within the esophagus of affected individuals. Patients present with symptoms of increasing dysphagia that progress from solid foods to liquids. Reference article...
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Esophageal carcinoma

Esophageal carcinoma is relatively uncommon. It tends to present with increasing dysphagia, initially to solids and progressing to liquids as the tumor increases in size, obstructing the lumen of the esophagus. Epidemiology Esophageal cancer is responsible for <1% of all cancers and 4-10% of a...
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Esophageal mass (mnemonic)

A mnemonic to remember the causes of an esophageal mass is: CALL the MVP Mnemonic C: carcinoma A: adenoma L: lymphoma L: leiomyoma M: metastasis V: varices P: papilloma/polyp
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Oligometastases

Oligometastases refers to distant disease that is limited in number and distribution, Niibe et al. defined this as ≤5 metastatic/recurrent lesions with control of the primary lesion 1,2. These metastases can be treated with local measures (surgery, radiation therapy, etc.) with the aim of increa...
Article

Oligoprogression

Oligoprogression is an increasingly recognized concept in oncology, denoting a state where after an initially successfully systemic therapy of disseminated metastases, a single or very few lesions display further progression.  Terminology A key difference between the related concepts of oligom...
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Omental cake

Omental cake refers to infiltration of the omental fat by material of soft-tissue density. The appearances refer to the contiguous omental mass simulating the top of a cake. Masses on the peritoneal surfaces and malignant ascites may also be present.  Pathology The most common cause is metasta...
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Ommaya reservoir

Ommaya reservoir, also known as Ommaya shunt, is a device consisting of an intraventricular catheter connected to a reservoir (port) implanted beneath the scalp. It is used for intrathecal administration of medication such as chemotherapy (mainly in the treatment of meningeal lymphomas, but also...
Article

Optic nerve enlargement

Enlargement of the optic nerves is uncommon and has a surprisingly broad differential: optic nerve glioma optic nerve meningioma orbital pseudotumor optic neuritis sarcoidosis leukemia orbital lymphoma metastases perioptic hemorrhage Erdheim-Chester disease juvenile xanthogranuloma m...
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Optic nerve sheath meningioma

Optic nerve meningiomas are benign tumors arising from the arachnoid cap cells of the optic nerve sheath and represent ~20% of all orbital meningiomas, the majority of which are direct extensions from intracranial meningiomas.  These tumors typically appear as masses within the optic nerve, iso...
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Oral cavity carcinoma (staging)

Oral cavity carcinoma staging refers to TNM staging of carcinomas involving the oral cavity. The vast majority of applicable cases are squamous cell carcinomas, but other epithelial and minor salivary gland cancers are also included. The following article reflects the 8th edition published by th...
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Orbital metastasis

Orbital metastases are relatively uncommon, but some primary tumors do have a predilection to metastasize to the orbit. This article concerns itself with extraocular metastases, rather than intraocular tumors or direct extension of tumors from neighboring regions. For a discussion of intraocula...

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