Squamous carcinoma in a major salivary gland has several possible sources: (1) high-grade mucoepidermoid carcinoma, (2) metastasis or direct invasion from a primary skin carcinoma, (3) metastasis from a distant primary carcinoma, or (4) a primary malignant neoplasm. The latter is conventionally regarded as a diagnosis of exclusion after a history of squamous carcinoma elsewhere has been obtained or there is a positive mucin stain.
Eleven cases of squamous carcinoma in a major salivary gland are presented and the literature reviewed.
Two cases, 1 metastatic from a histologically identical squamous carcinoma from the ipsilateral tonsil and 1 with in situ squamous carcinoma in a duct, demonstrated positive mucicarmine stains. Two cases were high-grade mucoepidermoid carcinomas, also with positive mucin stains. Five cases represented metastases from cutaneous squamous carcinomas. Only 2 cases were regarded as primary carcinomas. There were no histologic clues as to correct subclassification. Six patients died, 4 from their disease. Three of the 5 still alive had recurrence or metastasis.
The occurrence of squamous carcinoma in a major salivary gland exhibits a histologic sameness that precludes accurate subclassification and assignation of origin. Also irrespective of tumor origin, the clinical approach to diagnosis and treatment is similar. Adjuvant therapy (eg, radical neck dissection, radiation, chemotherapy) is not uniformly applied. Most patients present with a sizable (>3-cm) mass for which total excision is attempted. The natural evolution of the tumor is aggressive, irrespective of clinical context. The traditional subclassification of squamous carcinoma in a major salivary gland may not be clinically relevant.