This image is from a transurethral resection specimen showing dilated vascular spaces containing atypical lymphoid cells. The diagnosis made with the help of immunohistochemical studies was intravascular large B-cell lymphoma. The tumor cells proliferate predominantly within small vessels. Any organ may be infiltrated. Central nervous system and skin are frequently involved. Prostatic involvement (shown here) is rare. Most patients are elderly and present at advanced stages. The tumor is highly aggressive and proves rapidly fatal if not treated promptly.