A blue nevus is a benign melanocytic lesion that is composed of spindle-shaped pigmented melanocytes. Although the uterine cervix is believed to be the most common extracutaneous location of blue nevi, the occurrence of these lesions in the endometrial stroma has been reported, albeit rarely. The present study describes a case of endometrioid adenocarcinoma concurrent with a blue nevus of the endometrium and uterine cervix. A 58-year-old female presented with abnormal vaginal bleeding. A biopsy from the endometrium revealed an endometrioid adenocarcinoma and subsequently, a total hysterectomy was performed. Histopathological study revealed the proliferation of columnar cells that formed irregularly-shaped tubular and cribriform glands. The neoplastic columnar cells had large, round to oval nuclei containing a single small nucleolus. Focal squamous differentiation was noted. In the stroma of the non-neoplastic endometrium, single or small aggregates of short spindle-shaped cells containing melanin without atypia were observed. These melanocytes were also present in the endocervix. Therefore, the final diagnosis was of endometrioid adenocarcinoma concurrent with a blue nevus of the endometrium and cervix. This is the first documented case of a blue nevus of the endometrium and endocervix. The pathogenesis of blue nevi of the genital tract is not yet completely understood. Possible origins of these cells include Schwann cells or perineural cells of the peripheral nerve fiber or the abnormal migration of neural crest-derived cells.
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