MUCINOUS SYRINGOMETAPLASIA - AN IMMUNOHISTOCHEMICAL AND ULTRASTRUCTURAL-STUDY OF A CASE

Mucinous syringometaplasia (MS) is an unusual skin lesion of unknown e tiology, characterized histologically by epidermal invaginations lined by mucin-laden goblet-like cells and by nonkeratinized squamous cells . The present case study was performed to elucidate further the charac teristics of this lesion using immunohistochemistry and electron micro scopy. The mucin-laden cells in the MS lesion stained positively for c arcinoembryonic antigen, epithelial membrane antigen, and low molecula r weight keratins. The ultrastructural examination, which was performe d on deparaffined sections, revealed two morphological variants of muc ous granules. Electron-dense mucous granules predominated in the mucus -containing cells, which were situated among the keratinocytes adjacen t to the epidermal invaginations, mostly in the lower parts of the epi dermis. Larger, electron-lucent granules containing flocculent materia l were found more abundantly in the cells lining the epidermal invagin ations. Also, some of the mucus-containing cells showed bundles of ton ofilaments; structures that appeared to be isolated short, stubby micr ovilli; and attachments to adjacent mucus-containing cells and keratin ocytes by desmosomes. The ultrastructural and immunohistochemical find ings in our case suggest that the mucinous changes occurred as a metap lastic process in the resident epidermal cells and were accompanied by changes in cellular antigen expression resembling those of simple sec retory epithelium.