Introduction:
Although neoplasms of the salivary glands are relatively rare, they are
nevertheless characterized by a variety of biologies and prognoses.
According to the most recent WHO classification of salivary gland
tumors, these are mostly benign but they can nevertheless present with
different grades of malignancy. Secretory carcinoma (SC), a malignant
tumor affecting the salivary glands of the head and neck, was recently
reclassified in the light of molecular analysis in 2017; before that
date it was considered a mammary analogue secretory carcinoma (MASC).
Acinic cell carcinoma (ACC) is a low grade salivary gland malignancy
characterized by serous acinar differentiation. It is important to
understand the growth patterns and the differences between SC and ACC as
they are similar histologically. Unlike ACC, SC pathognomonically
expresses the ETV6-NTRK3 gene fusion, a characteristic permitting
pathologists to formulate the diagnosis of a SC with regards to a lesion
originally considered ACC. Although both SC and ACC are characterized by
a generally favorable prognosis and non-aggressive behavior, high grade
SC tumors have been described, and, according to some reports, they are
characterized by a higher rate of lymph node involvement and distant
metastases. Since it has only recently been reclassified, SC may be
confused with other tumors of the salivary glands and incorrectly
diagnosed. The current work, which reports on a case of SC of the
submandibular gland originally diagnosed as a low grade mucoepidermoid
carcinoma, examines some of its clinical, genetic and
immunohistochemical features.