Diagnosis: Leiomyosarcoma
• Leiomyosarcomas must demonstrate some evidence of smooth muscle differentiation. This is demonstrated histologically by observation of fascicles of cigar-shaped spindle cells with scant to abundant eosinophilic cytoplasm. Coagulative necrosis is the most important factor in determining malignancy in a smooth muscle tumor (in the absence of confounding history such as leuprolide therapy). In the absence of coagulative necrosis, a high mitotic rate (10 mitotic figures/10 high-power fields), nuclear pleomorphism, and increased cellularity all must be present to support the diagnosis.
• Uterine sarcomas represent approximately 3% of all uterine malignancies. Of the uterine sarcoma group, leiomyosarcoma is most common.
• Most leiomyosarcomas occur in women who are older than 40 years of age. The most common presenting symptoms are abnormal vaginal bleeding, a palpable pelvic mass, and pelvic pain. These clinical symptoms can often be indistinguishable from leiomyoma, and it may be difficult to make a preoperative distinction.
• Leiomyosarcoma variants include epithelioid and myxoid. Both variants can show lower than expected mitotic rates. The epithelioid variant often lacks necrosis. The myxoid variant is often paucicellular. These features can hinder correct diagnosis.
• Tumor size and mitotic index are important prognostic factors when predicting leiomyosarcoma-related morbidity and mortality. Ki-67 is also a biologically significant prognostic marker because increased Ki-67 rates correlate with increased disease-related mortality. P16 is also identified at a much higher rate in leiomyosarcomas than it is in leiomyomata or normal myometrium.
• Dedifferentiated leiomyosarcomas are high-grade leiomyosarcomas with a uniformly poor prognosis.
