A unique combined mastocytoma-junctional nevus presented as a 4-mm dark brow n macule in the axilla of a 57-year-old white female. Histopathologic examinat ion revealed a proliferation of mast cells partially or compl...A unique combined mastocytoma-junctional nevus presented as a 4-mm dark brow n macule in the axilla of a 57-year-old white female. Histopathologic examinat ion revealed a proliferation of mast cells partially or completely filling the d ermal papillae,hyperpigmentation of the basal keratinocytes and mildly increased basal melanocytes. Overlying the mast cell proliferation, pigmented junctional nevus nests were present. The mast cells were strongly positive with Giemsa stai n and mast cell tryptase immunohistochemical stain; nevomelanocytic cells were n egative. Nevomelanocytes were strongly immunoreactive for S100, HMB-45, Mart-1 , and tyrosinase; mast cells were negative. The clinicopathologic features sugge sted a synchronous proliferation of 2 cell types in the same small cutaneous fie ld rather than a collision tumor. While the cutaneous mast cells probably origin ated as a disseminated clone,itispostulatedthat local mast cell growth factor in duced nevomelanocytic proliferation and modulated mast cell growth. In fact, the tumor exhibited strong immunoreactivity for the mast cell growth factor recepto r (CD117) in mast cells, basal melanocytes, and nevus nests. The incidence of du al mast cell-melanocytic tumors appears to be very low, as only 3 total cases h ave now been reported. However, since in patients with multiple mastocytomas onl y a small fraction of lesions are biopsied, the true incidence may be higher tha n supposed.展开更多
文摘A unique combined mastocytoma-junctional nevus presented as a 4-mm dark brow n macule in the axilla of a 57-year-old white female. Histopathologic examinat ion revealed a proliferation of mast cells partially or completely filling the d ermal papillae,hyperpigmentation of the basal keratinocytes and mildly increased basal melanocytes. Overlying the mast cell proliferation, pigmented junctional nevus nests were present. The mast cells were strongly positive with Giemsa stai n and mast cell tryptase immunohistochemical stain; nevomelanocytic cells were n egative. Nevomelanocytes were strongly immunoreactive for S100, HMB-45, Mart-1 , and tyrosinase; mast cells were negative. The clinicopathologic features sugge sted a synchronous proliferation of 2 cell types in the same small cutaneous fie ld rather than a collision tumor. While the cutaneous mast cells probably origin ated as a disseminated clone,itispostulatedthat local mast cell growth factor in duced nevomelanocytic proliferation and modulated mast cell growth. In fact, the tumor exhibited strong immunoreactivity for the mast cell growth factor recepto r (CD117) in mast cells, basal melanocytes, and nevus nests. The incidence of du al mast cell-melanocytic tumors appears to be very low, as only 3 total cases h ave now been reported. However, since in patients with multiple mastocytomas onl y a small fraction of lesions are biopsied, the true incidence may be higher tha n supposed.
