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.

Mucin histochemistry of the lower gastrointestinal tract.

Variations in the mucin secretion pattern in the mucosal lining of the colon and rectum have been studied. Mucins have been differentiated histochemically as neutral mucins, sialomucins and sulphomucins, using alcian blue/PAS and HID/alcian blue techniques. In the normal colonic mucosa, the goblet cells secrete predominantly sulphomucins with small amounts of sialomucins. Twenty one cases with benign lesions showed varying patterns of mucin secretion. In the 35 cases with adenocarcinoma studied, the transitional mucosa adjacent to the lesion showed a reversal of mucin secretion pattern, with an increase in sialomucins and a marked decrease in sulphomucins, suggesting a reaction to neoplasia.