Melanocytic Lesions with Special Reference to Malignant Melanoma

Abstract

Problems sometimes arise in diagnosing malignant melanoma because it is a great mimic and can resemble several other kinds of tumour, including carcinoma (Nottingham and Slater, 1988), sarcoma (Landas and Urdaneta, 1991; Jones et al., 1995; Zelger et al., 1997; King et al., 1999) and lymphoma (Wang et al., 2007). Malignant melanoma is also known to exhibit a great diversity of morphology (Nakhleh et al., 1990; Perniciaro, 1997; Banerjee and Harris, 2000), shows many unusual variants (Magro et al., 2006) and exhibits divergent differentiation (Banerjee and Eyden, 2008). Most malignant melanomas are readily diagnosed on the basis of clinical findings, light microscope morphology and immunophenotype: mostly, they contain epithelioid, oval or spindled cells and express an immunophenotype in which the most important markers are HMB-45, Melan-A and S100 protein (Hachisuka et al., 1986; Jundt et al., 1986; Angeli et al., 1988; Ordöñez et al., 1988; Wick et al., 1988; Orosz, 1999; Orchard, 2000; Yaziji and Gown, 2003). Other markers, which some investigators may prefer or which have shown a transient popularity, include tyrosinase, microphthalmia transcription factor (Chang and Folpe, 2001; O’Reilly et al., 2001; Granter et al., 2002), NKIC3 (Mackie et al., 1984; van Duinen et al., 1984; Gatter et al., 1985; Vennegoor et al., 1985; Hagen et al., 1986; Henzen-Logmans et al., 1988; Bishop et al., 1993; Orchard, 2000) and neurone specific enolase (NSE) (Rode and Dhillon, 1984; Hirano, 1986). Malignant melanomas are also vimentin positive (Caselitz et al., 1983; Huszar et al., 1983; Miettinen et al., 1983; Ramaekers and Jap, 1983; Henzen-Logmans et al., 1988) but this is so non-specific as to be of limited diagnostic value. Other less well known malignant melanoma proteins include the cell adhesion molecules, IIb-IIIa-like glycoprotein (McGregor et al., 1989), Mel-CAM (Koch et al., 2001) and stem cell markers such as CD133, CD166 and nestin (Klein et al., 2007)