Ovarian smooth muscle metaplasia: an uncommon and possibly underrecognized entity.

Smooth muscle differentiation in the ovary is rare, and its histopathologic spectrum, including ovarian smooth muscle metaplasia (SMM), has not been well described. The clinicopathologic findings in 48 ovaries with SMM from 40 women are reported. The average age of women with ovarian SMM was 55.6 years (range, 34 to 86 years). Foci of SMM were semiquantitatively characterized as 1+ in 46% (1 to 3 foci), 2+ in 37% (4 to 6 foci), and 3+ in 17% (> 6 foci). SMM was bilateral in 8 (23%) of the 35 patients who had bilateral oophorectomies. SMM was intimately associated with another ovarian process in 28 (58%) cases, including ovarian cysts (11), endometriosis (3), granulosa cell tumors (3), extensive stromal luteinization (1), ovarian fibroma (1), adhesions (1), and folliculogenesis (8). Ovaries with 2+ to 3+ SMM were associated with another ovarian lesion significantly more often than those with 1+ SMM (p < 0.01). Most women with ovarian SMM (86%) also had uterine leiomyomas. Significant endometrial pathology was present in 13 (37%) of 35 simultaneously removed uteri. In conclusion, SMM occurs most often in perimenopausal or postmenopausal women, most of whom also have uterine leiomyomas. Ovarian SMM is usually confined to a few microscopic fields, is bilateral in < 25% of patients, and is often associated with other ovarian lesions.