Another case of intravascular large B-cell lymphoma involving the prostate. This proved to be significantly more challenging than the previous case. When neoplastic lymphoid cells are tightly packed within vessel lumina, they may appear like cohesive islands of tumor mimicking carcinoma as seen here. An extended immunohistochemical panel resolved the issue. The tumor cells were: POSITIVE for CD45, CD20, and CD30 (shown here). They were NEGATIVE for: CAM5.2, PSA, PSAP, S-100, HMB-45.