Cellular blue nevus of the uterus: a case report and review of the literature.

Cellular blue nevus is extremely rare in the gynecologic tract with only 2 cases reported thus far, one in the myometrium and the other in the cervix/vagina/hymenal ring. In this report, we present the clinicopathologic features of the second case of cellular blue nevus arising in the myometrium. The patient was a 48-year-old woman who underwent a hysterectomy with bilateral salpingo-oophorectomy for uterine leiomyomas. On gross examination, the uterus showed a subserosal, 1.0×0.5×0.3 cm, dark red nodule in the anterior uterine wall in addition to multiple leiomyomas. Microscopically, the subserosal dark nodule had an irregular contour with only focal areas of pushing circumscribed border. The tumor cells were arranged either in sheets or confluent nests. The tumor cells were mostly epithelioid with clear cytoplasm, but in some areas the tumor cells were spindle-shaped with eosinophilic cytoplasm. Both types of cells contained intracytoplasmic melanin. The nuclei of the tumor cells were either oval, round, or elongated with no or minimal irregularities of the nuclear membrane, evenly distributed chromatin, inconspicuous nucleoli, and no obvious mitotic figures. Focally some of the epithelioid cells showed enlargement of the nucleus, irregularities in the nuclear contour, and rare nuclear pseudoinclusions. The tumor cells were positive for S-100, HMB-45 antigen (strong and diffuse pattern), and MART-1. Anti-Ki-67 showed a low proliferative activity (only a rare cell marked for this immunomarker). Thus, a diagnosis of cellular blue nevus was established. After a follow-up of 2 months, the patient had no evidence of the disease.