title: Myoepithelial carcinoma (malignant myoepithelioma) of the parotid gland arising in a pleomorphic adenoma.
abstract: A myoepithelial carcinoma, a rare malignant salivary gland neoplasm, arose in a pleomorphic adenoma of the parotid gland. The initial tumour was a pleomorphic adenoma with epithelial and myoepithelial elements. Subsequently the tumour recurred twice and was characterised by invasion of the mandible. Histological examination of the second recurrence showed a malignant spindle cell neoplasm with an infiltrative growth pattern and a high mitotic rate. There was involvement of local lymph nodes. The immunophenotype was characteristic of myoepithelial differentiation: tumour cells stained positively with anticytokeratin antibodies, S-100 protein, alpha smooth muscle actin, and vimentin. Electron microscopy confirmed myoepithelial differentiation, with small foci of keratinocytic phenotype. Large numbers of tumour cell nuclei were reactive with the anti-p53 antibody, DO-7, in contrast to the two previous resections. Thus malignant transformation of a pleomorphic adenoma may involve myoepithelial as well as epithelial elements. Accumulation of p53 protein, perhaps through mutational events, may have played a role in this malignant transformation.
authors.affiliation: Department of Pathology, Royal Group of Hospitals Trust, Belfast, Northern Ireland, UK.
authors.forename: W G
authors.initials: WG
authors.lastname: McCluggage
authors.forename: W J
authors.initials: WJ
authors.lastname: Primrose
authors.forename: P G
authors.initials: PG
authors.lastname: Toner
mesh_terms: D008949:Adenoma, Pleomorphic / Q000473:pathology* / Q000601:surgery; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008339:Mandibular Neoplasms / Q000473:pathology* / Q000601:surgery; D008854:Microscopy, Electron; D008875:Middle Aged; D009208:Myoepithelioma / Q000473:pathology* / Q000601:surgery; D009364:Neoplasm Recurrence, Local / Q000473:pathology* / Q000601:surgery; D009378:Neoplasms, Multiple Primary / Q000473:pathology* / Q000601:surgery; D010307:Parotid Neoplasms / Q000473:pathology* / Q000601:surgery; D009418:S100 Proteins / Q000032:analysis; D016159:Tumor Suppressor Protein p53 / Q000032:analysis
chemical_list: D009418:S100 Proteins; D016159:Tumor Suppressor Protein p53