Smooth Muscle Tumors
Gene Landon, MD
Key Facts
Clinical Issues
Mostly in pelvis and retroperitoneum of middle-aged/elderly individuals
Cytopathology
Low-grade leiomyosarcoma (LMS): Plump spindle cells with cigar-shaped nuclei and fibrillar/finely granular cytoplasm, ± perinuclear vacuoles
High-grade LMS: ± atypia, mitoses, necrosis, pleomorphism
± nuclear indentations, ± myxoid stroma, ± palisading
Ancillary Tests
Positive: Desmin, SMA, muscle specific actin, calponin, caldesmon, ± keratin, ± EMA
Top Differential Diagnoses
Leiomyoma, nerve sheath tumors, GI stromal tumor, desmoid fibromatosis, solitary fibrous tumor
 (A) Pap-stained FNA smear of leiomyosarcoma (LMS) shows a fascicular fragment of spindle cells. (B) Romanowsky-stained FNA smear of LMS shows crowded, ovoid and elongated nuclei in a tumor fragment. (C) Pap-stained FNA smear of LMS shows mostly blunt-ended  elongated nuclei with granular chromatin and indistinct nucleoli. (D) Pap-stained FNA smear of LMS shows tumor nuclei in a background of finely fibrillar cytoplasmic processes. |
TERMINOLOGY
Abbreviations
Leiomyosarcoma (LMS)
Definitions
Malignant neoplasm of cells with smooth muscle differentiation
