The top radiological differential was lymphoma, based on the mass 'creeping' around the upper abdominal structures, gently sandwiching them, rather than overly infiltrating. Although the proximal pancreas is difficult to separate out from the mass, the pancreatic duct is not dilated and therefore the lack of the 'double duct' sign would make a pancreatic primary less likely. Other differentials considered were Tuberculosis and IGG4 disease. The mass was subsequently core biopsied under ultrasound guidance and the histology report showed:

This core biopsy of abdominal mass is entirely lesional comprising diffuse sheets of medium to large cells with moderate nuclear pleomorphism, variable numbers of prominent nucleoli, apoptosis, with little discernible mitotic activity. Tumor necrosis is seen. There is no evidence of gland formation, mucin, keratin or pigment production. There is no identifiable vascular invasion.

Immunohistochemistry: positive Negative CD45 AE1/AE3 PAX8 CK 7 CK 20 CDX2 TTF-1 Gata-3 S-100

This immunohistochemical profile it is of a non-epithelial tumor strongly positive for pan-lymphoid marker CD45 and PAX8 strong positivity; in keeping with non-Hodgkin's lymphoma and would be most suggestive of diffuse large B-cell lymphoma, however referral to haematopathology will now take place for further typing of this lymphoma.

Final Diagnosis

A. ABDOMINAL MASS: non-Hodgkin's lymphoma suggestive of diffuse large B cell Type

Addendum Diagnosis

Biopsy from abdominal mass: High grade B cell lymphoma with MYC, BCL2 and BCL6 expression. The morphological features would be consistent with diffuse large B cell lymphoma, ABC subtype. FISH analysis is to follow. 

Addendum Comment

Haematopathology review:

These are core biopsies from a lymphoid lesion showing a diffuse growth pattern and composed of atypical large lymphoid cells with multiple small nucleoli and moderate amount of cytoplasm. Apoptotic cells are seen.

The atypical lymphoid cells are positive for CD20, BCL6, BCL2, C-MYC and MUM1 and appear negative for CD5, cyclin D1, CD10, CD30 and EBER. No FDC meshworks are seen in the background. Ki67 is about 90%.