Solitary fibrous tumor of the prostate

Abstract

36歳男性.患者は排尿困難を主訴とした.尿道造影, CT, MRIで膀胱内へ突出する腫大した前立腺を認め, 経直腸超音波下前立腺針生検で良性繊維性腫瘍と診断され, 経尿道的前立腺切除術が施行された.病理組織像は核異型のない紡錘形細胞の密な増生で, 分裂像は認めなかった.更に免疫組織染色でCD34が陽性, αSMAとデスミンが陰性のため病理組織診断は前立腺の良性孤立性線維性腫瘍とされた.現在, 術後より6年間が経過しているが再発なく健在である

Solitary fibrous tumor of the prostate is extremely rare. Only five cases have been reported to the present. A 36-year-old man presented to our hospital complaining of difficulty in urination. Retrograde urethrography and urethroscopy demonstrated intraurethral protrusion of the left prostatic lobe and complete obstruction of prostatic urethra. Magnetic resonance imaging demonstrated the prostatic tumor with prominent intravesical protrusion. Transrectal echo-guided biopsy was performed on the supposition of leiomyosarcoma of prostate. However, the tumor was diagnosed as benign fibrous tumor, so the patient underwent transurethral resection of left prostatic lobe for the purpose of improving urinary condition, avoiding retrograde ejaculation. Histologic examination revealed a dense proliferation of spindle cells with no nuclear atypia. No mitotic figure was seen. The pathologic diagnosis was benign solitary fibrous tumor of the prostate, because the tumor was positive for CD34 and negative for alpha-smooth muscle actin and desmin by immunohistochemical study. The patient remained well without regrowth of the tumor during the last six years.