Melanin containing cells of the uterine cervix and a possible histogenesis--a case report.

A 30 year old nulligravidfemale attended gynaecological OPD for investigation of primary infertility. Local examination revealed presence of a dark pigmented area in the posterior lip of the cervix. The biopsy from cervix showed, squamous metaplasia of the lining epithelium with presence of granules of melanin pigment in the basal layer. Schmorl's stain for melanin and immunohistochemical staining for S-100 and HMB-45 showed strong positivity in these cells. Melanosis of the uterine cervix is usually an incidental finding in females with uterine prolapse in their fifth and sixth decade. The origin of melanin containing cells in the uterine cervix is debatable till date. Amongst the various possibilities for the origin of these cells in the uterine cervix, neural origin is probably more acceptable than epithelial cell origin. The combined expression of melanocytic and Schwanian markers in the index case, suggest a biphasic differentiation of melanin containing cells in the uterine cervix. Although the exact histogenesis and clinical significance of these are still unknown, a long term follow-up is needed to study the nature of these lesions to look for any precursor lesion for development of malignant melanoma.