Mitotic activity in expanded human skin.

In 20 patients subjected to breast reconstruction by means of tissue expansion, a skin biopsy was obtained at the vertex of the breast before and the day after expansion. Samples were incubated in [3H]thymidine, and the number of labeled cells were counted. A statistically significant rise in the number of labeled basal and suprabasal keratinocytes was seen after expansion. The findings suggest a net gain of tissue not only by stretching but also by formation of new tissue generated by tissue expansion.