Secretory breast carcinoma with a papillary-predominant pattern: an unusual morphological variant

Secretory breast carcinoma is a rare, low-grade, translocation-associated invasive carcinoma with unique morphology and excellent prognosis. Three patterns (microcystic, tubular, solid) have often been described in secretory carcinoma. Herein, we reported one case of secretory breast carcinoma with an uncommon papillary-predominant growth pattern.

The patient was a 53-year-old female with a mass located in outer upper quadrant of her right breast. The patient had one positive axillary lymph node. Morphologically, tumour cells were arranged in a papillary growth pattern with sclerosis in most areas; glandular and microcystic patterns were observed only in focal areas at the periphery. The presence of intracellular and extracellular secretory material was observed. Tumour cells were mild-to-moderately atypical with granular eosinophilic to foamy cytoplasm. Tumour cells were triple-negative [negative for oestrogen receptor (ER), progestogen receptor (PR) and human epidermal growth factor receptor 2 (HER2)] with a basal-like phenotype, and strongly positive for S-100 protein. P63 and calponin staining showed the absence of myoepithelial cells around tumour cells. Fluorescence in-situ hybridization (FISH) analysis showed ETS variant 6 (ETV6) gene rearrangement.

Our study indicated that besides typical growth patterns (microcystic, solid and tubular), secretory carcinoma could also present with a papillary-predominant architecture. These cases should be differentiated from other breast tumours with a papillary pattern. It may have clinical significance to recognize this uncommon morphology variant of secretory carcinoma in routine practice.