Basaloid lesions of oral squamous epithelial cells and their association with HPV infection and P16 expression.

UNLABELLED: Basaloid squamous cell carcinoma is a variant of squamous cell carcinoma, preferentially arising in the head and neck region. Current reports point to an association of basaloid squamous cell carcinoma (BSCC) and human papilloma virus (HPV) infection. This virus is supposed to be an aetiological factor in this entity. The aim of this study was to analyse the HPV infection status in different entities of oral neoplasms or dysplasias with basaloid differentiation of epithelial cells. MATERIALS AND METHODS: The study comprised data from 34 oral lesions of squamous epithelial origin: 17 BSCCs, 10 papillomas and 7 hyperplasias/dysplasias of oral epithelia. HPV DNA was detected by means of a hybrid capture technique. HPV types were identified by direct sequencing. Immunohistochemical investigation of the specimens with anti-p16 antibody was performed in order to elucidate the putative role of p16 as a surrogate marker of HPV infection. RESULTS: The rate of HPV-infected BSCC was extraordinarily high. About two thirds of the cases (61%, 11/17) were infected with HPV high-risk types, predominantly with HPV genotype 16 (>90%, 10/11). The infection status differed significantly between BSCC and other oral lesions in terms of frequency of HPV infection and HPV genotypes. p16 expression proved not to be a suitable surrogate marker of HPV high-risk infection in oral lesions, in particular in BSCC. This was an essential difference of this collective compared to genital carcinomas with HPV high-risk infections. CONCLUSION: This study revealed a high association between BSCC and HPV type 16. This close phenotype-genotype correlation could be of diagnostic value. Type-specific analysis of HPV infection in head and neck cancer may be important in the differential diagnosis of malignancies in the head and neck region with a basaloid growth pattern. However, the investigation is technically demanding, including hybridisation and sequencing techniques. A simplified test for HPV in BSCC of the oral cavity using the immunohistochemical proof of p16 expression as a surrogate marker is non-effective.

Relative paucity of gross genetic alterations in myoepitheliomas and myoepithelial carcinomas of salivary glands.

The diagnosis of salivary gland myoepithelioma, an entity with heterogeneous cytomorphology and inconsistent immunophenotype, rests on conventional histology. However, the clinical course cannot be predicted reliably from cytomorphological and immunophenotypic analysis. The present study determined the immunophenotype of a representative series of 12 myoepitheliomas and 21 malignant myoepitheliomas. Among the seven markers tested, antibodies against cytokeratins 5/6, S-100 protein, and vimentin produced the most consistent reactivity profile. Comparative genomic hybridization (CGH) profiles of 12 myoepitheliomas showed chromosomal losses in three of 12 cases. In myoepithelial carcinomas, however, ten of 19 tissues investigated by CGH lacked detectable cytogenetic aberrations. In five cases, aberrations involved chromosome 8, in line with observations in salivary gland carcinomas of other differentiation. One case that was represented in three separately localized manifestations of the disease proved informative as to the relevance of gross aberration for tumour development, as these tumours differed in their CGH profiles. Staining for cytokeratins 5/6 is a useful addition to the established immunohistological marker panel in the work-up of myoepitheliomas, because of its reliable expression in most cases and because it may underline the epithelial nature of the lesion. CGH proved to be of limited value as a diagnostic adjunct; the presence of numerous gross cytogenetic aberrations should raise the suspicion of malignancy. The low frequency of aberrations detectable by CGH in overtly malignant myoepithelial neoplasms suggests that gross cytogenetic alterations were acquired in the course of tumour progression and points to the relevance of genetic changes not resolved by CGH.