[Clinicopathologic and molecular genetic analysis of secretory carcinoma of salivary gland].

Objective

To investigate the clinicopathologic and molecular genetic features of secretory carcinoma of salivary gland (SCSG).

Methods

Six cases of SCSG were collected from Zhejiang Provincial People's Hospital from January 2011 to March 2018. The clinical, histopathological and immunohistochemical features were analyzed and fluorescence in situ hybridization (FISH) was used to detect ETV6 gene rearrangement.

Results

Four out of 6 tumors originated in the parotid gland and one of each in the minor salivary glands of soft palate and the buccal mucosa. Grossly, 4 cases were solid and 2 were partially cystic with maximum diameter ranging from 1.0 to 4.0 cm. Microscopically, 5 tumors showed typical features of low grade SCSG with tumor divided by thin fibrous septa into lobules composed of solid acinar, microcystic, follicular and papillary structures with abundant extracellular mucinous secretions. The tumor cells had cuolated or hobnail cytoplasm with low-grade nuclei and scarce mitoses. Perineural invasion was present in 1 case. The remaining tumor showed about 30% of the tumor areas with high-grade transformation characterized by proliferation of a distinct population of anaplastic cells arranged in irregular glandular, small nested and single cell patterns that were surrounded by desmoplastic stroma and invaded into surface mucosa with ulceration. Immunohistochemistry showed that all 6 tumors had diffuse and strong reactivities to S100 protein and cytokeratin 7, and 4 cases showed focal reactivity to gross cystic disease fluid protein 15 (GCDFP15), all were negative for discovered on gist 1 (DOG1), cytokeratin 20, p63 and calponin. High grade transformation cases were analysed, the high grade SCSG components showed a significantly increased Ki-67 index and cyclin D1 positive tumor cells compared to the conventional SCSG components. FISH analyses showed that 4 cases had ETV6 gene rearrangement. Eleven to seventy one months' follow-up showed no evidence of tumor recurrence nor metastasis.

Conclusions

SCSG harbors characteristic genetic abnormalities with ETV6 gene rearrangement and typically shows a low grade morphology with occasionally, high grade transformation can be present.