Adenocarcinoma, NOS, is a salivary gland carcinoma that shows glandular or ductal differentiation but lacks the prominence of any of the morphologic features that characterize the other, more specific carcinoma types. The diagnosis of adenocarcinoma, NOS, is essentially one of exclusion. In an AFIP review of cases, adenocarcinoma, NOS, was second only to mucoepidermoid carcinoma in frequency among malignant salivary gland neoplasms. Other series have reported an incidence of 4% to 10%. In AFIP files, the mean patient age was 58 years. Approximately 40% and 60% of tumors occurred in the major and minor salivary glands, respectively. Among the major salivary gland tumors, 90% occurred in the parotid gland. Adenocarcinoma, NOS is graded in a similar way to extrasalivary lesions according to the degree of differentiation. Tumor grades include low grade, intermediate grade, and high-grade categories.
Patients with tumors in the major salivary glands typically present with solitary, painless masses. Two retrospective studies indicate that survival is better for patients with tumors of the oral cavity than for those with tumors of the parotid and submandibular glands.[35,36] These studies differ regarding the prognostic significance of tumor grade.
Basal cell adenocarcinoma
Basal cell adenocarcinoma, also known as basaloid salivary carcinoma, carcinoma ex monomorphic adenoma, malignant basal cell adenoma, malignant basal cell tumor, and basal cell carcinoma, is an epithelial neoplasm that is cytologically similar to basal cell adenoma but is infiltrative and has a small potential for metastasis. In AFIP case files spanning almost 11 years, basal cell carcinoma comprised 1.6% of all salivary gland neoplasms and 2.9% of salivary gland malignancies. Nearly 90% of tumors occurred in the parotid gland.[3,37] The average age of patients is reported to be 60 years.
Similar to most salivary gland neoplasms, swelling is typically the only sign or symptom experienced. A sudden increase in size may occur in a few patients. Basal cell carcinomas are low-grade carcinomas that are infiltrative, locally destructive, and tend to recur. The carcinomas occasionally metastasize. In a retrospective series that included 29 patients, there were recurrences in 7 patients and metastases in 3 patients. In another retrospective review that included 72 patients, 37% of the patients experienced local recurrences. The overall prognosis for patients with this tumor is good.[37,38]
Clear cell carcinoma
Clear cell carcinoma, also known as clear cell adenocarcinoma, is a very rare malignant epithelial neoplasm composed of a monomorphous population of cells that have optically clear cytoplasm with standard hematoxylin and eosin stains and lack features of other specific neoplasms. Because of inconsistencies in the methods of reporting salivary gland neoplasms, meaningful incidence rates for this tumor are difficult to derive from the literature. Most cases involve the minor salivary glands.[1,3,39,40,41] In the AFIP case files, the mean age of patients is approximately 58 years.