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Malignant tumors of the uterine corpus are broadly divided into carcinomas and sarcomas. Although sarcomas are rarely encountered, they tend to behave more aggressively and contribute to a disproportionately higher number of uterine cancer deaths. Pure sarcomas differentiate toward smooth muscle (leiomyosarcoma) or toward endometrial stroma (endometrial stromal tumors). In general, uterine sarcomas grow quickly, hematogenous or lymphatic spread occurs early, and the overall prognosis is poor. However, there are several notable exceptions among these tumors.
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EPIDEMIOLOGY AND PATHOGENESIS
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Sarcomas account for approximately 3 to 8 percent of all malignancies of the uterine corpus (Brooks, 2004; D’Angelo, 2010; Major, 1993). Historically, uterine sarcomas included carcinosarcomas, accounting for 40 percent of cases; leiomyosarcomas, 40 percent; endometrial stromal sarcomas, 10 to 15 percent; and undifferentiated sarcomas, 5 to 10 percent. In 2009, the International Federation of Gynecology and Obstetrics (FIGO) reclassified carcinosarcomas as a metaplastic form of endometrial carcinoma. These tumors are described in Chapter 33 (p. 708).
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Because of their infrequency, uterine sarcomas have few identified risk factors. These include chronic excess estrogen exposure, tamoxifen use, African American race, and prior pelvic radiation. In contrast, combination oral contraceptive pill use and smoking appear to lower risks for some of these tumors (Felix, 2013).
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In their pathogenesis, leiomyosarcomas have a monoclonal origin, and for the most part, they do not arise from benign leiomyomas. Instead, they appear to develop de novo as solitary lesions (Zhang, 2006). Supporting this theory, leiomyosarcomas have molecular pathways distinct from those of leiomyomas or normal myometrium (Cui, 2017). The most consistent findings across molecular studies involve functional loss of RB1 and PTEN, which are tumor suppressor genes (El-Rifai, 1998; Gibault, 2011).
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Endometrial stromal tumors have heterogeneous chromosomal aberrations (Halbwedl, 2005). However, the pattern of rearrangements is clearly nonrandom, and chromosomal arms 6p and 7p are frequently involved (Micci, 2006). Genetic translocations involving several chromosomes and the resultant fusion proteins are thought to be involved in endometrial stromal sarcoma pathogenesis (Lee, 2012; Panagopoulos, 2012).
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As in endometrial cancer, abnormal vaginal bleeding is the most frequent symptom for uterine sarcomas (Gonzalez-Bosquet, 1997). Pelvic or abdominal pain also is common. Up to one third of women will describe significant discomfort that may result from passage of clots, rapid uterine enlargement, or prolapse of a sarcomatous polyp through an effaced cervix (De Fusco, 1989). In addition, a profuse, foul-smelling discharge may be obvious, and gastrointestinal and genitourinary complaints are frequent. Importantly, degenerating leiomyomas with necrosis can mimic these same signs and symptoms.
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With rapid growth, a uterus may extend out of the pelvis into the mid- or upper abdomen (...