Background: The presence of melanin-containing cells is an occasional finding in the female genital tract. The origin and clinical significance of these cells are debatable and still unknown. These lesions are described under various designations from benign to malign, such as melanosis, stromal melanocytosis or blue nevus and malign melanoma either primary or metastatic. The occurrence of melanin-containing cells in the endometrial stroma, which is designated as a blue nevus of the endometrium, has been documented only twice previously. However, searching the literature for melanosis of the endometrium, namely melanin detection in both stromal and epithelial cells, not a single report was found.
Case Report: A 45-year-old woman, having oligomenorrhea for the past 2 years, and who eventually had profuse bleeding, underwent endometrial curettage. Our case was an incidental finding of small aggregates of short spindle cells with finely granular, dark brown pigment in the curettage specimen. The histochemical characteristic of the pigment was melanin, and was also noted both within the glandular epithelial and the stromal cells.
Conclusions: As a consequence, our lesion from the endometrium might be the first documented example of extracutaneous endometrial melanosis.

Keywords: Endometrium, Melanosis, melanin, stroma, glandular epithelium