CUTANEOUS FOCAL MUCINOSIS - A HISTOPATHOLOGICAL AND IMMUNOHISTOCHEMICAL ANALYSIS OF 11 CASES

The histogenesis of cutaneous focal mucinosis (CFM) is controversial. Eleven cases of CFM (5F, 6M; mean age 51 years) from our routine files between 1986 and the present time have, therefore, been examined hist opathologically and immunohistochemically. Histology revealed an incre ased number of fibroblast-like cells in early lesions, whereas they we re diminished or predominantly at the margin in advanced ones. The myx omatous areas showed slight to absent reticulum formation. Similarly, elastic fibers were almost absent, and collagen fibers were fragmented and replaced by variable amounts of mucin. One specimen revealed an e pithelial component within the lesion reminiscent of a poorly induced trichofolliculoma. Immunohistochemically, vimentin was consistently pr esent and correlated with the number of fibroblast-like cells. A few ( <5%) CD34(+) dermal dendritic cells (DDs) were focally seen within CFM . In contrast, FXIIIa(+) DDs accounted for up to 30%. Fibroblast-like cells were negative for S-100 protein, Leu7, desmin and alpha-SMA. The epithelial component within one of our specimens seems to have been i nduced by CFM and is a feature also seen in (angio)-myxomas. CFM appea rs to be a mesenchymally derived lesion composed predominantly of fibr oblasts. DDs do not form the major cell component but rather seem pass ively incorporated.