Diagnostic and Therapeutic Perspectives on Parotid Mammary Analog Secretory Carcinoma: Two Case Reports and Literature Review.

Abstract

Mammary analog secretory carcinoma (MASC) is a rare malignant tumor of the salivary glands that exhibits significant morphological, immunohistochemical, and molecular similarities with secretory carcinoma of the breast, including the characteristic ETV6-NTRK3 gene fusion. The diagnosis of this condition remains challenging due to its histopathologic overlap with other low-grade salivary gland tumors, such as acinic cell carcinoma and mucoepidermoid carcinoma. The following report details two cases of MASC manifesting in the right parotid gland of a 37-year-old male and a 23-year-old female. Both subjects exhibited slow-growing, painless swellings and radiologic findings indicative of benign lesions. The surgical excision procedure was performed on the first patient via extracapsular dissection, while the second patient underwent superficial parotidectomy. Both procedures were carried out under the supervision of intraoperative facial nerve monitoring. A subsequent histopathological and immunohistochemical examination revealed a glandulocystic growth pattern with eosinophilic secretions and strong immunoreactivity for CK7, S100, and mammaglobin. Although molecular testing for the ETV6-NTRK3 fusion was not performed, the clinical, morphological, and immunophenotypic findings supported the diagnosis of low-grade secretory carcinoma. The patients exhibited uncomplicated recovery, with transient facial nerve paresis in the second patient resolving within 3 months. The first patient remains disease-free after 40 months of clinical and radiological follow-up, while the second patient has shown no evidence of recurrence after 21 months of follow-up. The cases under consideration serve to emphasize the importance of integrating morphology and immunohistochemistry in routine practice, with molecular confirmation remaining the diagnostic gold standard whenever it is available. It is imperative to be aware of this entity to ensure an accurate diagnosis, optimal surgical management, and appropriate long-term surveillance. Emerging evidence suggests that targeted therapy with NTRK inhibitors may represent a promising option for advanced or recurrent disease.