Genetic markers of oral malignant melanoma analysed by fluorescence in situ hybridisation (FISH).

Oral malignant melanoma (OMM) is a rare condition, and our knowledge about morphological and genetic modifications is scanty and incomplete. The aim of this study is to report morphological and fluorescent in situ hybridisation (FISH) data obtained in four cases of OMM. FISH results were also compared with those of cutaneous malignant melanoma (CMM, three cases), desmoplastic cutaneous melanoma (DMM, four cases) and spindle cells cutaneous melanoma (SCCM, one case). All the OMM cases showed a combined radial and vertical growth pattern, with the invasive component characterised by malignant spindle cells intermingled among collagen bundles. Two cases of OMM resulted positively stained with p16, in contrast with frequent loss of immunoreactivity in CMM. Three OMM were suitable for FISH analysis: 9p21 locus was deleted in 1/3, 1p36 resulted deleted 3/3, while EGFR gene showed a relative deletion. Similar genetic alterations were found in DMM and SCMM, but not in CMM. Ultrastructural findings further enhanced differences between OMM and CMM; OMM displayed, mature-staged melanosomes only within in situ component. In conclusion, OMM presents a morphological and genetic profile similar to DMM; and SCCM, however, displays some differences from CMM.