This patient was worked up for possible lymphoma, and thus a CT-guided core-biopsy of the retroperitoneal masses was performed:
Macroscopy: "Retroperitoneal mass". Two pale tan cores of tissue and haemorrhage,
measuring <1mm and 5mm.
Microscopy: The biopsy fragments consist of fibrous connective tissue which includes an infiltrate of small reactive lymphocytes and a population a large atypical cells forming either sheets or poorly defined nests. These cells have irregular nuclear membranes with prominent nucleoli, and a small to moderate amount of pale cytoplasm. The large atypical cells show weak positive immunostaining for broad-spectrum cytokeratin (AE1/3). These immunomarkers are negative in the atypical cells: CD20, CD5, Bcl2, cyclinD1, CD10 (lymphoma markers) and S100 (melanoma marker).
Conclusion: Retroperitoneal mass, core biopsy - Probable metastatic poorly differentiated carcinoma. Additional immunostains show positive tumour cell marking for PLAP, with no staining for CD30, CK7, CK20 or pan-cytokeratin. Although the sample is small, the morphology and immunobinding are consistent with a diagnosis of metastatic seminoma.