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Carcinosarcoma

Carcinosarcoma, also known as true malignant mixed tumor, is a rare malignant salivary gland neoplasm that contains both carcinoma and sarcoma components. Either or both components are expressed in metastatic foci. Some carcinosarcomas develop de novo while others develop in association with benign mixed tumor. This neoplasm is rare; only eight cases exist in the AFIP case files.[3] At one facility, only 11 cases were recorded over a 32-year period.[8] The majority of tumors occur in the major salivary glands.

Swelling, pain, nerve palsy, and ulceration have been frequent clinical findings. Carcinosarcoma is an aggressive, high-grade malignancy. In the largest series reported, which consisted of 12 cases, the average survival period was 3.6 years.[8]

Metastasizing mixed tumor

Metastasizing mixed tumor is a very rare histologically benign salivary gland neoplasm that inexplicably metastasizes. Often a long interval occurs between the diagnosis of the primary tumor and the metastases. The histologic features are within the spectrum of features that typify pleomorphic adenoma.[3] The majority occur in the major salivary glands. The primary neoplasm is typically a single, well-defined mass. Recurrences, which may be multiple, have been reported to occur for as many as 26 years after excision of the primary neoplasm.[55]

Rare carcinomas

Primary squamous cell carcinoma

Primary squamous cell carcinoma, also known as primary epidermoid carcinoma, is a malignant epithelial neoplasm of the major salivary glands that is composed of squamous (i.e., epidermoid) cells. Diagnosis requires the exclusion of primary disease located in some other head and neck site; indeed, most squamous cell carcinomas of the major salivary glands represent metastatic disease.[3] This diagnosis is not made in minor salivary glands because distinction from the more common mucosal squamous cell carcinoma is not possible.[3] Previous exposure to ionizing radiation appears to increase the risk for developing this neoplasm.[11,56] [57] The median time between radiation therapy and diagnosis of the neoplasm is approximately 15.5 years.[11] The reported frequency of this tumor among all major salivary gland tumors has varied from 0.9% to 4.7%.[3,10] In AFIP major salivary gland accessions from 1985 to 1996, primary squamous cell carcinoma comprised 2.7% of all tumors; 5.4% of malignant tumors; and 2.5% and 2.8%, respectively, of all parotid and submandibular tumors.[3] The average age in the AFIP registry was 64 years.[3] This neoplasm occurs in the parotid gland almost nine times more often than in the submandibular gland.[3,57] There is a strong male predilection.[3,11,57] [58,59] This tumor is graded in a similar way to extrasalivary lesions according to the degree of differentiation, namely, low, intermediate, and high.[1]