American Urological Association - Rhabdomyosarcoma
- Most common prostate tumor in the first 2 decades of life (ave. 7 years); very rare in adults.
- Presents with obstructive urinary symptoms.
- Gross: fleshy tumor with history of rapid growth.
- May initially present as a polypoid mass in prostatic urethra and can mimic a fibroepithelial polyp.
- Most commonly embryonal type, alveolar type less common.
- Embryonal RMS shows sheets of "small round blue cells"* with scattered "strap cells" or "tadpole cells" having cross-striations (rhabdomyoblasts) (image A) & (image B).
- Alveolar RMS shows anastomosing fibrous septa (like lung air spaces) and the tumor cells populate the alveolar spaces.
- Express desmin and skeletal muscles markers myoD1 and myogenin.
- About 2/3 of alveolar RMS will show t(2;13) and t(1;13).
- Prognosis is related to histologic type and tumor stage.
- Alveolar RMS has poorer prognosis.
- In contrast to pediatric RMS, adult RMS does not appear to respond to multimodal therapy and has a poorer prognosis.
- 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-).