Most patients present with an asymptomatic mass in the parotid region. Other symptoms may include a painful mass and facial nerve palsy. The prognosis for this neoplasm is poor. In a 30-year retrospective analysis of 50 cases of squamous cell carcinoma of the salivary glands, survival rates at 5 years and 10 years were 24% and 18%, respectively.
Epithelial-myoepithelial carcinoma, also known as adenomyoepithelioma, clear cell adenoma, tubular solid adenoma, monomorphic clear cell tumor, glycogen-rich adenoma, glycogen-rich adenocarcinoma, clear cell carcinoma, and salivary duct carcinoma, is an uncommon, low-grade epithelial neoplasm composed of variable proportions of ductal and large, clear-staining, differentiated myoepithelial cells. The tumor comprises approximately 1% of all epithelial salivary gland neoplasms.[3,60] It is predominantly a tumor of the parotid gland. In the AFIP case files, the mean age of patients is about 60 years and about 60% of the patients are female.
Localized swelling is commonly the only symptom, but occasionally patients experience facial weakness or pain.[61,62] Overall, epithelial-myoepithelial carcinoma is a low-grade carcinoma that recurs frequently, has a tendency to metastasize to periparotid and cervical lymph nodes, and occasionally results in distant metastasis and death.[60,62,63,64]
Anaplastic small cell carcinoma
Anaplastic small cell carcinoma of the salivary glands was first described in 1972. Subsequent histochemical and electron microscopic studies have supported the neuroendocrine nature of this tumor.[66,67] Microscopically, the tumor cells have oval, hyperchromatic nuclei and scant amount of cytoplasm and are organized in sheets, strands, and nests. The mitotic rate is high. Neuroendocrine carcinomas are more frequently found in the minor salivary glands and have a better survival rate compared with small cell carcinomas of the lung. The undifferentiated counterpart of this neoplasm is the small cell undifferentiated carcinoma.
Undifferentiated carcinomas of salivary glands are a group of uncommon malignant epithelial neoplasms that lack the specific light-microscopic morphologic features of other types of salivary gland carcinomas. These carcinomas are histologically similar to undifferentiated carcinomas that arise in other organs and tissues. Accordingly, metastatic carcinoma is a primary concern in the differential diagnosis of these neoplasms.
Small cell undifferentiated carcinoma
Small cell undifferentiated carcinoma, also known as extrapulmonary oat cell carcinoma, is a rare, primary malignant tumor that, with conventional light microscopy, is composed of undifferentiated cells and, with ultrastructural or immunohistochemical studies, does not demonstrate neuroendocrine differentiation. This is the undifferentiated counterpart of anaplastic small cell carcinoma (Refer to the anaplastic small cell carcinoma section of this summary.)
In an AFIP review of case files, small cell carcinoma represented 1.8% of all major salivary gland malignancies; the mean age of patients was 56 years. In 50% of the cases, patients present with an asymptomatic parotid mass of 3 months' or less duration.[68,69,70] This is a high-grade neoplasm. In a retrospective review of 12 cases, a tumor size of more than 4 cm was found to be the most important predictor of behavior. In another small retrospective series, estimated survival rates at 2 and 5 years were 70% and 46%, respectively.