Salivary gland microsecretory adenocarcinoma: a case series study and literature review.

Microsecretory adenocarcinoma (MSAd) is a recently described, low-grade salivary gland malignancy primarily involving intraoral sites, characterized by consistent morphological and immunohistochemical features, as well as the MEF2C::SS18 fusion. This study reported five new MSAd cases and reviewed previously reported MSAd cases affecting the maxillofacial region. Most of the patients in this case series study were male, with the palate being the most affected intraoral location. All cases showed uniform histological features and immunophenotype associated with S100, SOX10, p63, AE1/AE3, and CK7 positivity, and p40, c-KIT, and calponin negativity. Focal SMA and mammaglobin expressions were observed in one case each. Perineural and vascular invasion were uncommon findings. All MSAd cases were MEF2C::SS18 fusion positive. A literature review identified 44 head and neck MSAd cases, encompassing both salivary gland and cutaneous tumors. Some previously reported MSAd cases displayed subtle variations in their histopathological and immunohistochemical characteristics, underscoring the importance of molecular fusion confirmation. Given its typically indolent behavior, MSAd patients can be managed similarly to those with other low-grade salivary gland carcinomas.