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.

Melanosis coli--histochemical and immunohistochemical comparison of the pigments of melanosis coli and Dubin-Johnson syndrome

We compared the pigment of melanosis coli with the pigment of Dubin-Johnson syndrome, melanin, and lipofuscin. The pigment of melanosis coli appeared similar to lipofuscin in that it stained positively with periodic acid-Schiff, oil red-0 and Victoria blue stains and revealed negative reactions to the immunohistochemical stains for S-100 protein and neuron specific enolase, but had similarity to melanin as shown by the positive reaction to Fontana-Masson stain and negative autofluorescence. The pigment of Dubin-Johnson syndrome showed the same histochemical and immunohistochemical characteristics as that of melanosis coli. The results indicate that the pigments of melanosis coli and Dubin-Johnson syndrome are identical and are variants of lipofuscin.