Intravascular large B cell lymphoma of prostate, a rare entity.

Intravascular large B cell lymphoma is a rare type of extranodal lymphoma characterized by selective growth of neoplastic cells in small vessels, especially capillaries, sparing larger arteries, veins and surrounding tissue. The absence of intravascular lymphoma in the traditional sites and difference in mode of presentation with no mass forming lesion as compared to other lymphomas, makes it unique and difficult to diagnose early. It is extremely heterogeneous in its clinical presentation depending on the organ involved. Primary intravascular large B cell lymphoma of the prostate is extremely rare and only 8 cases have been reported in English literature till date, limited to single case reports. This is a rare case of a 76 year old male patient, who came with complaints of urinary obstruction and fever of unknown origin since 15 days. Routine investigations were within normal limits including the complete urine examination, complete blood picture and PSA levels. Mild prostatomegaly was noted on radiology. Patient was catheterized and transurethral resection was done. On histopathological examination, prostatic acini and stroma were normal but the vessels in the stroma which were dilated and thin walled lacking a muscular coat, showed sheets of loosely cohesive cells with moderate eosinophilic to clear cytoplasm, vesicular nuclei, with 1 to 3 prominent nucleoli and mitoses, averaging 4-6/hpf. On immunohistochemistry, the tumor cells were positive for CD 20 and MUM 1 with high MIB1 index of about 90% and were negative for CD3, CD10, Bcl6, PSA, P63, CK7, CK20, HMWCK, and Pancytokeratin. CD31 stained and highlighted the endothelial cells of the vessels. Final diagnosis made after correlating light microscopy and immunohistochemistry was a Primary Intravascular large B-cell lymphoma of the prostate.