May arise from periglandular tissues or prostatic capsule.
Rare, most occur in 60s presenting with obstructive symptoms.
May be mistaken clinically as BPH and encountered often in TUR.
Typically, solitary 2-7 cm, but can grow considerably large (>10 cm).
Gross: solitary, well circumscribed, white-tan with smooth outer surface.
Traditionally described in 2 forms, as solitary tumors and in background of BPH. (Those in BPH were probably "leiomyomatous" type hyperplasia).
Histology: fascicles of benign spindle cells with cigar-shaped nuclei.
Immunohistochemistry: smooth muscle marker actin+ and desmin+.
Rarely, exhibits polygonal or round cell morphology (leiomyoblastoma).
DDX: leiomyomatous BPH (multiple) and other spindle cell tumors.
Infrequent (<1%), but LMS together with rhabdomyosarcoma are the most predominant types of prostate sarcomas in adult.
Occur in 40s to 70s, but may occur in younger and pediatric patients.
Most presents with obstructive symptoms; also hematuria and weight loss.
LMS may grow large (mean 9 cm) and replace entire prostate; often is difficult to completely resect the tumor.
Dense fascicles of spindle cells with pleomorphic cigar-shaped nuclei, prominent nucleoli and abundant mitosis; higher grade tumors, fasciculations become vague.
Necrosis is common and tumors may undergo cystic degeneration
Immunohistochemistry: diagnosis confirmed by smooth muscle markers, such as actin+ and desmin+.
Aggressive course with 1-year survival of 55%.
DDX: other spindle cell tumors such as sarcomatoid carcinoma (keratin+), stromal sarcoma (CD34+, actin-), GIST (c-kit+) and SFT (CD34+, actin-).