Giant microcystic adnexal carcinoma of the scalp.

Microcystic adnexal carcinoma (MAC) is an uncommon, locally aggressive tumor. It typically involves the upper lip of middle-aged adults, and in rare instances the scalp. We report a Japanese woman with a giant MAC on the scalp. Physical examination revealed a 110 mm x 120 mm induration on her parietal region. Microscopically, the tumor showed both pilar and sweat gland differentiation. Resection included the cranium; for reconstruction we used a titan mesh allograft and covered it with a free latissimus dorsi muscle flap and a mesh skin graft. Ours is the first case of a MAC measuring more than 100 cm2 arising on the scalp of an individual in the third decade of life.

Merkel cell-nerve cell interaction undergoes formation of a synapse-like structure in a primary culture.

Merkel cells have been assumed to guide nerve fibers to the skin. However, there has been little in vitro evidence that supports this hypothesis, because there is no suitable established culture system of Merkel cells. Here we show that Merkel cells isolated from rat footpad skin were successfully cultured in a monolayer with keratinocytes. Keratinocytes did not affect any structural changes in Merkel cells. When nerve cells (NG108-15 or PC12) were added to the culture system, both nerve fibers and cytoplasmic processes of Merkel cells outgrew and cooperatively organized synapse-like structures at their contact points. Nerve cells promoted Merkel cell survival, compared with keratinocytes only. Merkel cell proliferation was not detected in all conditions, even with nerve growth factor, neurotrophin-3, interleukin-6 and tumor necrosis factor-alpha. The data suggest, firstly, that Merkel cells may guide nerve fibers to the skin by interacting with nerve cells; and, secondly, that nerve cells, but not keratinocytes, may produce some survival factors other than the cytokines above for Merkel cells, although Merkel cells may be a terminally differentiated cell type. Our method could open a way to study Merkel cell biology.