Clinicopathologic features of micropapillary variant of pure mucinous carcinoma of breast

Objective To study the clinicopathologic features of pure mucinous carcinomas of the breast with diffuse micropapillary pattern.Methods Twenty-six cases of micropapillary variant of pure mucinous carcinoma of the breast were retrospectively reviewed by light microscopy,immunohistochemistry and clinical data analyses.Results The age of 26 female patients ranged from 30 to 77 years old,of which 12 cases with clinical details available were mean 54 years old.The tumor diameter ranged from 0.8 to 9.0 cm (mean 3.2 cm).Ipsilateral axillary nodal metastases were identified in 3 cases.Cutaneous involvement was also found in 2 cases.The tumor cells showed the similar architectural arrangement as in invasive micropapillary carcinoma,with peripheral borders of the cell clusters highlighted by epithelial membrane antigcn.Various amount of mucin occupied the retraction spaces around the tumor cells.Compared with conventional pure mucinous careinoma of the breast,mucinous carcinomas with micropapillary pattern showed different nuclear grades (19 cases of grade Ⅰ,2 cases of grade Ⅱ,5 cases of grade Ⅲ).The micropapillary cell clusters varied in size (22 cases of big micropapillary and 4 cases of small).Intraductal carcinoma was observed in 12 cases.Calcification and psammoma bodies were observed in 8 cases.Immunophenotyping,the tumor cells were with higher expression of hormonc rcccptors,but HER2 were negative.Ki-67 positive index was 1％ ～ 70％.Neuroendocrine differentiation was observed in 6 cases.ConcLusions The micropapillary variant of pure mucinous carcinoma of the breast,which mainly occurs in younger women,may carry the similar propensity for angioinvasion and nodal metastasis as infiltrating micropapillary carcinoma at least in cases with high nuclear grade.This morphologic subtype needs to be distinguished from conventional pure mucinous carcinoma of the breast and treated properly. Key words: Breast neoplasms;  Carcinoma, papillary;  Immunophenotyping;  Prognosis