Mucinous breast carcinoma is a rare histologic subtype of primary breast cancers accounting for 2% of all breast carcinomas. It is usually associated with a better prognosis than other invasive breast neoplasms

Aims: 

In this study, we describe the pathological, immunohistochemical and molecular features of this rare tumour with review of the literature.

 

Materials and Methods:

This is a retrospective study of three patients with primary mucinous breast carcinoma collected in the anatomy pathology department over a period of 5 years from January 2015 to January 2019. Pathological diagnosis was determined by HE staining. The immunohistochemical expression of ER, PR, HER2 and Ki67 was assessed in 3 patients.

Results:

The total number of patients diagnosed with mucinous breast carcinoma were 3. Age ranged from 40-62 years with the median age 50,66 years. One case had tumour sizes ranging 1-2cm (pT1c) and two cases with >5cm (pT3). Histological examination allowed us to identify 3 pure mucinous breast cancers (two cases with type A and one case with type B). Observation for lymph node metastasis confirmed that two cases were pN0 (negative) and one were pN2. The tumours were classified according to The Bloom-Richardson grading as grade I in one case of mucinous carcinoma and as grade II in 2 cases. 2 cases of mucinous breast cancer were ER positive, EP positive and HER2-negative but one case was ER-negative, EP-négative and HER2 negative. Molecular analysis of these tumors revealed tow cases with the luminal A subtype.

Conclusion:

Mucinous carcinoma is a rare variant of invasive breast carcinoma. It is of the luminal A molecular subtype and associated with a favorable prognosis. However, due to the limited number of cases in this study, more investigations with larger cohorts should be performed to involve molecular and biological characterizations.