Myoepithelial carcinoma of the retromolar area with extensive mandibular involvement

Imaging of Malignant Minor Salivary Gland Tumors of the Head and Neck

Minor salivary gland carcinomas (MSGCs) are nonminor tumors in the head and neck region and account for about half of all salivary gland carcinomas. Imaging evaluation based on the anatomy of minor salivary and mucous glands in the head and neck region as well as invasion patterns in each site helps in identifying optimal treatment modalities and planning suitable treatment strategies. MSGCs can be divided radiologically into localized and invasive subtypes on the basis of the clinical utility of such categorization. Characteristic invasion patterns of the invasive type include deep submucosal extension, bone marrow infiltration, and perineural spread, which are difficult to assess clinically. MSGCs easily invade adjacent structures because of their submucosal location and may spread along the muscles, nerves, periosteum, and dura mater. Moreover, the tumor may spread into the bone marrow without obvious bone destruction. In addition to imaging classification, examining the anatomy and distribution of the minor salivary glands, including the palatal, lingual, buccal, labial, and retromolar glands, as well as other mucous glands, including the glands of the sinonasal cavity and nasopharynx, lacrimal glands, ceruminous glands, laryngeal glands, and tracheal glands, facilitates MSGC diagnosis and tumor extension assessment. The authors review the precise anatomy of the minor salivary and mucous glands in the head and neck region, discuss the MSGC imaging classifications, and describe how to evaluate the extent of MSGCs in each site on the basis of the imaging classification and invasion patterns. ^©RSNA, 2020.

Myoepithelial Carcinoma of the Salivary Glands: A Clinicopathologic Study of 29 Patients

PURPOSE

Myoepithelial carcinomas (MECs) of the salivary glands are relatively rare. The clinicopathologic features, immunohistochemical profile, and biologic behavior have not been well-defined.

MATERIALS AND METHODS

A total of 29 patients with MEC diagnosed during a 10-year period were included in the present study focusing on the biologic behavior, and the pathologic samples of 28 patients were collected for additional investigation of the histologic characteristics. Thirteen samples with detailed immunohistochemical results were included for illustrating immunohistochemical profiles.

RESULTS

The parotid gland (n = 7) was the most common site involved, followed by the palate (n = 6) and the submandibular gland (n = 6). A multinodular growth pattern (n = 14) and sheet-like arrangement of tumor cells (n = 14) were observed. Of the 28 MEC samples, 14 (50%) were epithelioid, 5 (18%) were clear cell, 5 (18%) were plasmacytoid, 3 (11%) were mixed cell type, and 1 (3%) was spindle. The tumor-associated matrix was more prevalently hyalinized than myxoid. Of the 28 cases, 12 (43%) were classified as high grade and 16 (57%) as low grade. Immunohistochemical analysis revealed pan-cytokeratin (92.3%), smooth muscle actin (36%), S-100 protein (54.5%), and p63 (91.7%) positivity and carcinoembryonic antigen (100%) negativity. Ki-67 was immunoreactive in 62% of the MECs, with the Ki-67 labeling index ranging from less than 5 to 20%. Eleven patients developed recurrence (median disease-free survival 43 months) and 11 (44%) developed metastases. Two patients (8%) died of disease after a mean period of 18 months. Fourteen patients (61%) were without any evidence of disease after a mean of 32.5 months (range 3 to 86). The mitotic rate correlated weakly (P = .042) with a poor outcome, but none of the other factors showed a significant correlation with the prognosis.

CONCLUSION

MECs of the salivary glands have a relatively high recurrence rate and metastasis rate and a long period of survival with tumor. A combination of pathologic features and various immunohistochemical indexes are crucial for the accurate diagnosis of MECs. Extensive excision is the favorable choice for treating MECs, and suprahyoid lymph node dissection is recommended when the submandibular gland is involved.