Low malignant intraductal carcinoma on the hard palate: a variant of salivary duct carcinoma?

A rare, minor salivary gland tumour of the hard palate in a middle-aged woman was presented. The small (1.0 X 0.5 cm in diameter) hemispherical tumour was well circumscribed with a fine papillomatous surface. Histopathologically, tumour cells with eosinophilic cytoplasm and a large nucleus were single-strand cuboidal and columnar cells, which showed intraductal growth exhibiting a cribriform pattern. The histological features were distinct from adenoid cystic carcinoma and polymorphous low-grade adenocarcinoma because the tumour lacked the neurotropic infiltration, cord-like proliferation and targetoid arrangement. The tumour could not be identified as a typical salivary-duct carcinoma because Roman bridging, papillary projection, and severe cell atypia were not found. Tumour cells were negative for PAS, Alcian blue, mucicarmine, p53, c-erbB-2, CEA, S-100 protein, alpha-smooth muscle actin, lactoferrin or vimentin. About 5% of the tumour cells were positive for proliferating cell nuclear antigen. Taking these factors into account, together with the clinical features, the name low malignant intraductal carcinoma seems appropriate.