Large solitary fibrous tumor of the seminal vesicle.

Solitary fibrous tumors show a classic morphologic pattern ("patternless pattern") consisting mainly of a proliferation of bland spindle cells with varying amounts of thick, often hyalinized or keloid-like, intercellular collagen bundles. Immunohistochemistry shows a strong reactivity for CD34 antigen, vimentin, and, in a variable percentage, bcl-2 antigen. We report the case of a 50-year-old man with a large solitary fibrous tumor located in the pelvic cavity with a rare nonspecific histologic pattern of pseudovascular formations. The patient underwent pelvic exenteration with orthotopic continent urinary diversion and sigmoid-J-pouch bowel reconstruction. No signs of tumor recurrence were noted within 24 months of surgery.