BACKGROUND: Malignant melanoma is notorious for the wide range of histologic patterns it can assume, among the least frequent of which is chondroid melamona. METHODS: Two cases of primary chondroid melanoma of the distal lower extremity were studied. Tissue for light microscopy was fixed in formalin, embedded in paraffin, and processed routinely. In one case, transmission electron microscopy and immunohistochemical evaluation were performed. RESULTS: Both cases exhibited melanoma in-situ, a conventional (non-chondroid) invasive component, and areas of chondroid differentiation, as confirmed by strongly positive staining with Alcian blue at pH 2.5 and Safranin O. Immunohistochemically, one case expressed S-100 protein and vimentin, and did not express gp100 (HMB-45), tyrosinase, MART-1, the Mel-5 antigen, the NKI/C3 antigen, CD45Ro, cytokeratin, or desmin. Electron microscopy of the chondroid component revealed occasional tumor cells with rare, membrane-bound, electron-dense organelles; the extracellular compartment showed amorphous ground substance consistent with cartilaginous differentiation. CONCLUSIONS: Chondroid change in the absence of osteogenic differentiation is extremely rare in malignant melanoma. Melanoma should be considered in the differential diagnosis of primary cutaneous neoplasms exhibiting cartilaginous differentiation.
BACKGROUND:Malignant melanoma is notorious for the wide range of histologic patterns it can assume, among the least frequent of which is chondroid melamona. METHODS: Two cases of primary chondroid melanoma of the distal lower extremity were studied. Tissue for light microscopy was fixed in formalin, embedded in paraffin, and processed routinely. In one case, transmission electron microscopy and immunohistochemical evaluation were performed. RESULTS: Both cases exhibited melanoma in-situ, a conventional (non-chondroid) invasive component, and areas of chondroid differentiation, as confirmed by strongly positive staining with Alcian blue at pH 2.5 and Safranin O. Immunohistochemically, one case expressed S-100 protein and vimentin, and did not express gp100 (HMB-45), tyrosinase, MART-1, the Mel-5 antigen, the NKI/C3 antigen, CD45Ro, cytokeratin, or desmin. Electron microscopy of the chondroid component revealed occasional tumor cells with rare, membrane-bound, electron-dense organelles; the extracellular compartment showed amorphous ground substance consistent with cartilaginous differentiation. CONCLUSIONS:Chondroid change in the absence of osteogenic differentiation is extremely rare in malignant melanoma. Melanoma should be considered in the differential diagnosis of primary cutaneous neoplasms exhibiting cartilaginous differentiation.
Authors: Parente Joana Devesa; José Manuel Pereira da Silva Labareda; Elvira Augusta Felgueira Leonardo Fernandes Bártolo; Maria Fernanda Sachse Pinto Fonseca Santos; Esmeralda Maria Seco do Vale Journal: An Bras Dermatol Date: 2013 May-Jun Impact factor: 1.896