AIM OF STUDY
Clinical and morphological analysis of patients with secretory carcinoma of the salivary gland with a demonstration of approaches to differential diagnosis and the use of molecular genetic methods.
MATERIALS AND METHODS
A retrospective analysis of salivary gland tumors was performed from the archive of the pathological and anatomical department of Moscow City Hospital No. 62 (Moscow) for the period from 2015 to 2019. If the tumor has histological characteristics corresponding to secretory carcinoma, according to the WHO classification (Lyon, 2017), an immunohistochemical study was performed with antibodies to S100, mammaglobin, p63, calponin, smooth muscle actin, Ki-67, as well as in situ fluorescence hybridization to detect ETV6 gene rearrangement using locus-specific probes.
RESULTS
From 308 cases of primary salivary gland tumors, 3 were identified that met the criteria for secretory carcinoma recommended by the WHO classification (Lyon, 2017) according to their histological characteristics. In 2 of 3 cases, the tumor was localized in the soft palate and in 1 case in the parotid salivary gland. In all cases, the disease was characterized by an indolent course, a slow tumor growth over a long time. The tumor is represented by a well-limited, unencapsulated nodular formation of a lobed appearance with clear contours, which was separated by layers of fibrous connective tissue. Tumor cells contained oxyphilic vacuolated or granular cytoplasm, nuclei with finely divided chromatin and a central location of well-defined nucleoli. An immunohistochemical study in all cases showed pronounced nuclear cytoplasmic coloring with antibodies to S100 and mammoglobin. Translocation t(12; 15)(p13; q25) and ETV6-NTRK3 gene fusion were confirmed by the FISH method in all three cases.
CONCLUSION
The presented analysis of clinical cases of salivary gland secretory carcinoma and a brief review of literature reflect the importance of diagnostic skills of the morphologist in identifying among the general stream of patients with solid tumors a specific group of patients who are most likely to rearrange the NTRK gene, which is associated with the possibility to use targeted therapy.
