Well-differentiated neuroendocrine tumors of the prostate also known as low-grade neuroendocrine carcinoma of the prostate or carcinoid tumors of the prostate are low-grade neuroendocrine tumors arising from the prostate that may metastasize.
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Epidemiology
Well-differentiated neuroendocrine tumors of the prostate are exceedingly rare 1-3.
Associations
A connection of well-differentiated neuroendocrine tumors with multiple endocrine neoplasias (MEN 2b) has been made in some of the cases 2-4.
Diagnosis
The diagnosis of well-differentiated neuroendocrine tumors of the prostate is based on histology and immunohistochemistry.
Clinical presentation
Prostate-specific antigen (PSA) as per definition should be negative and well-differentiated neuroendocrine tumors of the prostate might present with other symptoms such as voiding difficulties, dysuria. They might be also found incidentally on a histologic specimen or in conjunction with a prostate adenocarcinoma 4.
Pathology
Well-differentiated neuroendocrine tumors of the prostate show a similar tumor morphology as carcinoid tumors from other organs like the lung bladder or gastrointestinal tract and are different from usual prostate cancer. They are characterized by the following features 1-4:
- origin from prostate parenchyma and not from other organs
- distinct from prostate adenocarcinoma (that might coexist)
- positivity for neuroendocrine markers (synaptophysin, chromogranin A or CD56) and negativity for prostate-specific antigen (PSA)
Microscopic appearance
Microscopically well-differentiated neuroendocrine tumors of the prostate might display the following histological features 1,2,5:
- polygonal spindle-shaped cells
- small uniform nuclei
- microacinar or rosette-like growth pattern
- mixed architecture
Immunophenotype
Immunohistochemistry stains are usually positive for at least one neuroendocrine marker as synaptophysin, chromogranin A or CD56. They are negative for prostate-specific antigen (PSA) 1-4 and the Ki67 index is usually low. Some carcinoid tumors might express prostate-specific acid phosphatase 1-3.
Radiographic features
Due to their very rare occurrence, there are no suitable radiological descriptions of pure carcinoid of the prostate as yet. So if you come across such a rare entity with a histologically verified diagnosis please feel free to publish your case here and give us a description of your findings.
Radiology report
The radiological report should include a description of the following features:
- form, location and size
- tumor margins
- associated prostate cancer
Treatment and prognosis
Well-differentiated neuroendocrine tumors of the prostate are considered low-grade tumors but they are malignant and might metastasize to pelvic lymph nodes liver lungs or bone 4. Due to their rarity, there seems to be no consensus on the optimal treatment in cases without concomitant prostate cancer. Radical prostatectomy with follow up has been adopted in one case on 34-year-old man 4.
History and etymology
The first primary carcinoid tumor of the prostate was described by PW Wasserstein and RL Goldman in 1979 3,6.
Differential diagnosis
Conditions and tumors that can mimic the clinical presentation or imaging appearance of well-differentiated neuroendocrine tumors of the prostate include 1:
- carcinoid-like prostate adenocarcinoma
- other neuroendocrine tumors of the prostate
- carcinoid tumor of another organ with prostatic involvement
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