Merkel cells are integral constituents of Desmoplastic trichoepithelioma: an immunohistochemical and electron microscopic study

Abstract

The incidence of Merkel cells has previously been investigated in a number of inflammatory and tumorous lesions of the skin. Special attention was given to tumors with follicular differentiation. In the present study we examined the localization of Merkel cells in another adnexal tumor, the desmoplastic trichoepithelioma (n= 15), as well as in its main differential diagnosis, the morpheiform basal‐cell carcinoma (n=30). Using immunohistochemical methods, we found Merkel cells as a stable constituent in desmoplastic trichoepitheliomas, but failed to detect them in morpheiform basal‐cell carcinomas. These findings might therefore be an important tool in the sometimes very difficult but clinically imperative distinction between these two conditions. Furthermore, our study may be of interest in the discussion about the origin of desmoplastic trichoepitheliomas. High numbers of Merkel cells in desmoplastic trichoepitheliomas indicate a bulge‐derived origin of this adnexal tumor, since high numbers of Merkel cells, especially in the bulge, were recently discovered. Although the significance of Merkel cell hyperplasia in desmoplastic trichoepithelioma is not presently understood, a regulatory role of the Merkel cell in growth and development of this adnexal tumor is suggested.

Neural Hedgehog signaling maintains stem cell renewal in the sensory touch dome epithelium

“…Nonetheless, activation of Hh signaling was not sufficient to induce a Merkel cell tumor when SmoM2 was expressed in mouse Merkel cells and their progenitors. Interestingly, the neoplastic growths arising from SmoM2-expressing touch domes resemble trichoblastomas or trichoepitheliomas, benign epidermal tumors that can express K17 (42,43), can have up-regulation of Gli1 (44), and often are accompanied by scattered Merkel cells (45,46). Although these similarities are intriguing, we currently have no direct evidence to show that these tumors originate from touch domes in humans.…”

Evidence for Polymorphism of Merkel Cells in the Adult Human Oral Mucosa.

“…However, recent immunohistochemical studies using antibodies against cytokeratin markers specific for MCs, such as cytokeratins 8, 18, 19 and 20, have shown that the normally developing cutaneous anlagen frequently contain so-called dendritic MCs (DMCs) characterized by an irregular-shaped cell body and the protrusion of cytoplasmic processes (MOLL, R. et al, 1984, MOLL, I. et al, 1986NARISAWA et al, 1993a, b;KIM and HOLBROOK, 1995;VIELKIND et al, 1995). Similar DMCs have also been identified in terminal hair follicles of normal adult skin (NARISAWA et al, 1994a) and in hair follicles and follicle germs in pen-and intralesional skin samples from patients with desmoplastic trichoepithelioma, trichoblastoma, and nevus sebaceus (HARTSCHUH and SCHULZ, 1995;SCHULZ andHARTSCHUH, 1995, 1997). These DMCs have been presumed to have a stimulatory influence on the growth and proliferation of peripheral nerve fibers and/or epithelial cells (MOLL, R. et al, 1984;MOLL, I. et al, 1986;NARISAWA et al, 1993aNARISAWA et al, , b, 1994aKIM and HOLBROOK, 1995;HARTSCHUH and SCHULZ, 1995;SCHULZ andHARTSCHUH, 1995, 1997).…”

“…Similar DMCs have also been identified in terminal hair follicles of normal adult skin (NARISAWA et al, 1994a) and in hair follicles and follicle germs in pen-and intralesional skin samples from patients with desmoplastic trichoepithelioma, trichoblastoma, and nevus sebaceus (HARTSCHUH and SCHULZ, 1995;SCHULZ andHARTSCHUH, 1995, 1997). These DMCs have been presumed to have a stimulatory influence on the growth and proliferation of peripheral nerve fibers and/or epithelial cells (MOLL, R. et al, 1984;MOLL, I. et al, 1986;NARISAWA et al, 1993aNARISAWA et al, , b, 1994aKIM and HOLBROOK, 1995;HARTSCHUH and SCHULZ, 1995;SCHULZ andHARTSCHUH, 1995, 1997).…”

“…On the other hand, previous authors suggested that DMCs in the skin may serve to stimulate the growth or proliferation of peripheral nerves and epithelial cells, as these cells are usually present in developing fetal skin and in the bulge epithelium of adult hair follicles (MOLL, R. et al, 1984, MOLL, I. et al, 1986NARISAWA et al, 1993aNARISAWA et al, , b, 1994aKIVI and HOL BROOK, 1995;HARTSCIUH and SCHULZ, 1995;SCHULz andHARTSCHUH, 1995, 1997 HARTSCHUH et al, 1986;TACHIBANA, 1995). On the other hand, it is well known that these neuropeptides have modulatory actions on immunocytes (for reviews see: BLALOCK, 1989;GOETZL et al, 1990).…”

Advanced differentiation in trichoepithelioma and basal cell carcinoma investigated by immunohistochemistry against neurofilaments.

“…Literature is full of reports that offer diagnostic clues, but the fact that many of those clues are immunohistochemical [1][2][3][4][5][6][7][8][9][10][11], ultrastructural [12] or even molecular [13], gives the idea that the subject is far from being simple.…”