[Clinicopathologic features of secretory breast carcinoma]

Objective: Investigate the clinicopathological features for secretory carcinoma of breast (SCB). Methods: The clinical data of 3 SCB cases were collected, immunohistochemical staining was performed by the streptavidin-peroxidase (SP) method to test the expression of the antibodies: ER, PR, HER-2, Ki-67, S100, CK5/6, p63, SMA, calponin, GCDFP-15, and EGFR. Fluorescence in situ hybridization (FISH) was used to detect the ETV6-NTRK3 gene fusion. Results: ER was focal weakly positive in case 1 and case 2 (about 5%) , and negative in case 3. PR was focal weakly positive in case 1 (about 5%) and completely negative in case 2 and case 3. Three cases showed that HER-2, SMA, calponin, GCDFP-15 were negative, while S100, CK5/6, EGFR were diffuse strongly positive. The proliferation index was nearly 15% in case 1 and case 2, and 10% in case 3. p63 was negative in mostly tumor cells of case 1, and focal positive expression in the nucleus and cytoplasm. In case 2, p63 was completely negative. However, p63 was observed positive in the cytoplasm as well as some secretory material in case 3. ETV6-NTRK3 gene fusion detection by FISH was positive in all cases. Conclusions: SCB is a rare low grade triple-negative breast cancer with the unique pathomorphologic features, while its recurrent t (12; 15) (p13; q25) translocation resulting in ETV6 -NTRK3 gene fusion. It has the indolent clinical behavior and good prognosis.