Presentation
New onset of chest pain, over 2 months. Unremarkable past medical history. Elevated BMI.
Patient Data
There is an apparent cardiomegaly with an unusual cardiomediastinal contour. There are no signs of cardiac decompensation.
The aerated lung fields are clear.
The CT scanogram demonstrates the unusual "cardiomegaly" per the initial chest X-ray.
Multiphasic CT imaging confirms a large anterior mediastinal and prevascular mass of predominantly fat density typically "hanging down" on either side of the pericardium to reach the diaphragms inferiorly. The sagittal and coronal reformats demonstrate the scale of the mass extending from the superior mediastinum to the diaphragm and retrosternal to the posteroinferior thorax. There is no appreciative capsule, no calcification, no fat-fluid levels
There is scattered inhomogeneous and serpiginous, soft tissue density, minimally enhancing tissue, representing thymic tissue.
There are no calcifications and no fat-fluid levels. There are no suspicious mediastinal or hilar lymph nodes. There is compressive atelectasis, the lungfields are otherwise normal.
There is an incidental lobulated left breast mass lesion with associated calcifications.
The CT scanogram and reformats allude to the elevated BMI and obesity.
There are no osseous or upper hepatic metastases.
There is a calcified intrabdominal mass not fully characterised on the CT chest.
Image courtesy :Dr VKS Bhagwandas.
The post-operative chest X-ray at the time of follow-up demonstrates right mediastinal surgical clips and significant debulking of the right thymolipoma component. There is a post-surgical right basal effusion. The left thymolipoma component is still to be excised.
Macroscopy: a lobulated, encapsulated, fat-containing mass weighing 500g.
Microscopy: lobulated mature adipose tissue, surrounded in parts by a thin fibrous capsule, with interspersed islands of thymic tissue. No cyst formation, no perivascular spaces, no pleomorphism, no lipoblasts and no necrosis.
Immunochemistry:
A/E1/3- thymic epithelial cells identified
CD20- positive B-cells in foci of medullary differentiation present
TdT- positive, thymocytes highlighted
no malignancy or invasive tumour
Case Discussion
Features suggestive of a thymolipoma due to the presence of soft tissue density tissue scattered within the large fat density, anterior mediastinal mass. This was histologically confirmed on a surgical excision of the right mass. This yielded an encapsulated (surprisingly !) mass weighing approximately 500g and measuring 190 x 120 x 50mm. The patient is awaiting further left-sided excision at an elective stage.
Given the background elevated BMI and obesity, mediastinal lipomatosis is a considered differential diagnosis.
The remaining differentials of fat-containing mediastinal masses including teratoma, lipoma, and liposarcoma are considered unlikely.
The incidental breast mass was reassessed on a mammogram and breast ultrasound and a guided core biopsy revealed a hyalinised intracanalicular fibroadenoma (complex fibroadenoma).
A neurological examination with antibody correlation excluded Myasthenia gravis.
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