Do clinical and immunohistochemical findings of pure mucinous breast carcinoma differ from mixed mucinous breast carcinoma?

Mucinous carcinoma of the breast is a relatively rare histologic type with two subtypes: pure and mixed. It has a favourable prognosis with a low risk of axillary metastases. The prognosis for pure mucinous carcinoma (PMC) was much better than for the mixed mucinous carcinoma (MMC). The aim of the study is to determine suitable candidates for breast or axillary conservation in mucinous carcinoma subtypes. The slides of 26 pure and 23 mixed mucinous carcinomas of the breast were evaluated. The clinical, pathological and immunohistochemical features between PMCs and MMCs were compared. MMC displayed greater metastatic potential (p < 0.05), p53 positivity (p < 0.05) and c-erbB-2 positivity (p <0.001) than PMCs. PMCs smaller than 2 cm had less metastatic capacity and extranodal invasion compared to MMCs smaller than 2 cm (p < 0.001 and p < 0.01, respectively). MMCs smaller than 2 cm displayed weaker ER positivity but greater c-erbB-2 positivity than PMCs smaller than 2 cm (p < 0.01). In conclusion, MMC had worse prognostic factors than PMC with both types of mucinous carcinoma showing similar ER and PR positive status. Even if PMCs and especially smaller PMCs display more favourable prognostic features, including less axillary lymph node involvement, it is appropriate to use sentinel lymph node biopsy to make better axillary assessment.