American Urological Association - (Deep) Leiomyoma
- LM of deep soft tissues is uncommon and is most often found in the retroperitoneum.
- Patients are in 40s-60s; more common in women.
- Manifest as slow growing painless mass.
- Well-circumscribed gray-white tumor with no necrosis.
- Range 5-20 cm, retroperitoneal LM may grow big.
- Intersecting fascicles of deeply acidophilic spindle cells.
- Nuclei have blunt ends ("cigar-shaped") (image A) & (image B).
- No significant cellular pleomorphism.
- Retroperitoneal LM may have mitosis (but not >5/HPF).
- Immunohistochemistry: actin+, desmin+.
- True LMs are benign lesions that merely require excision with a small cuff of normal tissue.
- DDX: Other spindle cell tumors that are low-grade appearing.
- Schwannoma: wavy nuclei, hypo and hypercellular areas, Verocay bodies and S100+, actin-
- GIST: related to bowel wall, perinuclear vacoulations; CD117+, DOG1+.