Cutaneous adnexal and salivary gland tumours. Similarities and differences

Despite major discrepancies in basic microscopic anatomy, remarkable similarities are manifest within the wide spectrum of cutaneous adnexal and salivary gland tumors. In this study salivary gland and adnexal tumors were identified and investigated with respect to similarities in histology, terminology and pathogenesis. Histological similarities of certain types of salivary gland tumors relate to eccrine, apocrine and rarely sebaceous (but not trichofollicular) types of adnexal tumors. The most striking similarity was found with salivary gland pleomorphic adenoma and cutaneous mixed tumor. Multistep carcinogenesis starting with intraductal carcinoma, identified in carcinoma ex pleomorphic adenoma is identical to that found in cutaneous carcinoma ex spiradenoma. Further histological and terminological similarities are shown for mucinous and mucoepidermoid carcinoma, for lymphadenoma and lymphoepithelial carcinoma, for sebaceous adenoma and carcinoma, for adenoid-cystic carcinoma, as well as for salivary gland basal cell adenoma versus cutaneous spiradenoma. Manifest diagnostic problems related to histologically similar salivary gland and adnexal tumors are rare and are topographically limited to the parotid and oral areas.