Secondary anetoderma overlying pilomatrixomas.

Five pilomatrixomas with anetodermic cutaneous changes are presented. Four large tumors revealed soft, atrophic, pink translucent skin covering a firm subcutaneous mass, and their appearance was similar to that of a keloid or hypertrophic scar. One small tumor revealed soft, slightly atrophic, reddened or purplish skin covering a firm subcutaneous mass: its clinical appearance was similar to that of a hematoma or minor infection. Histopathological examination of the skin showed atrophic and edematous changes in the dermis associated with diminished fragmented collagen and absent elastic tissue. It is supposed that the dermal atrophic appearance bears a relation to the loss of elastic fibers and the dermal edema is related to the leakage of lymphatic fluid. Both phenomena may be caused by continuous pressure from the outside, as these anetodermic pilomatrixomas were located where they were apt to be exposed to mechanical irritation.