Large cell undifferentiated carcinoma
Large cell undifferentiated carcinoma is a tumor in which features of acinar, ductal, epidermoid, or myoepithelial differentiation are absent under light microscopy, though occasionally, poorly formed duct–like structures are found. This neoplasm accounts for approximately 1% of all epithelial salivary gland neoplasms.[3,53,71,72] Most of these tumors occur in the parotid gland.[70,72] In AFIP data, the peak incidence is in the seventh to eighth decades of life.
Rapid growth of a parotid swelling is a common clinical presentation. This is a high-grade neoplasm that frequently metastasizes and has a poor prognosis. Neoplasms 4 cm or larger may have a particularly poor outcome.[70,72]
Lymphoepithelial carcinoma, also known as undifferentiated carcinoma with lymphoid stroma and carcinoma ex lymphoepithelial lesion, is an undifferentiated tumor that is associated with a dense lymphoid stroma. An exceptionally high incidence of this tumor is found in the Eskimo and Inuit populations.[3,73] This neoplasm has been associated with Epstein-Barr virus infection.[74,75] Of the occurrences, 80% are in the parotid gland.
In addition to the presence of a parotid or submandibular mass, pain is a frequent symptom, and facial nerve palsy occurs in as many as 20% of patients. (Refer to the PDQ summary on Pain for more information.) Of the patients, more than 40% have metastases to cervical lymph nodes at initial presentation, 20% develop local recurrences or lymph node metastases, and 20% develop distant metastases within 3 years following therapy.[73,76,77,78]
Myoepithelioma carcinoma is a rare, malignant salivary gland neoplasm in which the tumor cells almost exclusively manifest myoepithelial differentiation. This neoplasm represents the malignant counterpart of benign myoepithelioma. To date, the largest series reported involves 25 cases. Approximately 66% of the tumors occur in the parotid gland.[3,74] The mean age of patients is reported to be 55 years.
The majority of patients present with the primary complaint of a painless mass. This is an intermediate grade to high-grade carcinoma.[3,79] Histologic grade does not appear to correlate well with clinical behavior; tumors with a low-grade histologic appearance may behave aggressively.
Adenosquamous carcinoma is an extremely rare malignant neoplasm that simultaneously arises from surface mucosal epithelium and salivary gland ductal epithelium. The carcinoma shows histopathologic features of both squamous cell carcinoma and adenocarcinoma. Only a handful of reports have discussed this tumor.
In addition to swelling, adenosquamous carcinoma produces visible changes in the mucosa including erythema, ulceration, and induration. Pain frequently accompanies ulceration. Limited data indicate that this is a highly aggressive neoplasm with a poor prognosis.