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.
Lymphomas and benign lymphoepithelial lesion
Lymphomas of the major salivary glands are characteristically of the non-Hodgkin type. In an AFIP review of case files, non-Hodgkin lymphoma accounted for 16.3% of all malignant tumors that occurred in the major salivary glands; disease in the parotid gland accounted for about 80% of all cases.
Patients with benign lymphoepithelial lesion (e.g., Mikulicz disease), which is a manifestation of the autoimmune disease, Sjögren syndrome, are at an increased risk for development of non-Hodgkin lymphoma.[80,81,82,83,84] Benign lymphoepithelial lesion is clinically characterized by diffuse and bilateral enlargement of the salivary and lacrimal glands. Morphologically, a salivary gland lesion is composed of prominent myoepithelial islands surrounded by a lymphocytic infiltrate. Germinal centers are often present in the lymphocytic infiltrate. Immunophenotypically and genotypically, the lymphocytic infiltrate is composed of B-lymphocytes and T-lymphocytes, which are polyclonal. In some instances, the B-cell lymphocytic infiltrate can undergo clonal expansion and evolve into frank non-Hodgkin lymphoma. The vast majority of the non-Hodgkin lymphomas arising in a background of benign lymphoepithelial lesions are marginal zone lymphomas of mucosa-associated lymphoid tissue (MALT).[81,82,83,84] MALT lymphomas of the salivary glands, like their counterparts in other anatomic sites, typically display relatively indolent clinical behavior.[3,85]