Atypical compound nevus arising in mature cystic ovarian teratoma

Mature cystic ovarian teratoma (MCOT) is the most common primary ovarian tumor. Rarely, MCOT may undergo malignant transformation. Melanoma arising primarily in MCOT is a rare event. Melanocytic nevi have also rarely been reported in MCOT.

A 28 year-old female presented with a palpable, 4.6 cm, right pelvic mass on physical examination. Histologically, the cystic neoplasm demonstrated epidermis with numerous pilosebaceous units and respiratory-type epithelium (endoderm) surrounded by adipose tissue and cartilage (mesoderm). A 2.0 x 1.0 cm pigmented area corresponded to a nevus with architectural and cytologic features of the so-called "dysplastic nevus," including variable-sized nests of nevomelanocytes irregularly distributed on distorted rete ridges, bridging of nests between rete ridges, fibroplasia around rete ridges, and junctional shouldering beyond the dermal nevus. The nevomelanocytes demonstrated moderate cytologic atypia. Diagnostic criteria of melanoma were not identified.

Herein, we report, to the best of our knowledge, the first case of an atypical ("dysplastic") nevus, arising in a MCOT. No features of melanoma were present and the patient is disease-free at one-year follow-up. Rarely, melanocytic nevi and melanomas arise from the ectodermal component of MCOTs. Moreover, melanomas may arise de novo or in association with a nevus. Distinction between a melanocytic nevus, as in our case, and a primary melanoma is critical for determining the patient's prognosis and need for additional therapy. As primary ovarian melanomas, like their skin counterpart, may arise from a precursor lesion, removal of a melanocytic nevus, such as this atypical nevus, could theoretically prevent melanoma transformation.