Lymphomas in prostate can be primary (35%) or secondary (48%).
Diagnosis as primary requires that:1) lymphoma involves prostate with no or minimal involvement of periprostatic tissue; 2) symptoms are attributable to enlarged prostate; and 3) no involvement of hematopoietic system (peripheral blood, lymph nodes, liver or spleen) within 1 month of diagnosis.
Incidental lymphoma may be seen in prostate with or without carcinoma.
Symptomatic patients present mainly with obstructive urinary symptoms and occasionally with hematuria.
Usually in men in their 60's.
Cystoscopically, may show urethral luminal narrowing and bladder trabeculation indistinguishable from those seen secondary to BPH.
Majority of incidental and concurrent (with known disease elsewhere) prostatic lymphomas are low-grade B-cell lymphomas.
Most primary lymphomas are diffuse large B-cell lymphoma (55% of primary and 37% of secondary) and small lymphocytic lymphoma (18% of primary and 27% of secondary).
Lymphomas tend to be diffuse and involve the fibromuscular stroma.
In marginal zone lymphoma, lymphoid cells may infiltrate the prostatic acini and form characteristic lymphoepithelial lesions.
DDX: chronic prostatitis, which mimics low-grade lymphomas.
Unlike lymphoma, chronic prostatitis is composed of polymorphous cells (mature T and B cells, large activated B cells, plasma cells and histocytes), has infiltrates with pushing borders and often is periglandular in location.
Immunohistochemistry: CD45, CD20 (for B cells) and CD3 (for T cells) will highlight lymphoid monoclonality (image D).
Reported lymphoma specific 1 and 5 years survivals were 64% and 33%, respectively.