Clinical significance of the sub-classification of 71 cases mucinous breast carcinoma

Abstract

Objective: Mucinous breast carcinoma (MBC) is classified into mixed mucinous breast carcinoma (MMBC) and pure mucinous breast carcinoma (PMBC) based on whether the tumor is with or without a component of invasive ductal carcinoma, respectively. PMBC is subtyped into hypocellular PMBC (PMBC-A) and hypercellular PMBC (PMBC-B).

Methods: Of 1,760 primary breast carcinomas, 71 were diagnosed as MBC, and were subtyped for comparison purposes.

Results: Seventy-one of all breast cancers (4.0%) were MBC, and consisted of 23 MMBC, 32 PMBC-A and 16 PMBC-B. The MBC tumors were more often hormone receptor-positive and HER2-negative than non-MBC tumors. Patients with MMBC, PMBC-B or PMBC-A, in this order, had significantly higher recurrence rates than non-MBC cases (p=0.006, log-rank).

Conclusions: In the NCCN guidelines, MBC is also regarded as "a histological type with a favorable prognosis" in a uniform manner, and "treatment for a histological type with a favorable prognosis" is recommended. However, the results of this study suggest that sub-classification-based, individualized therapeutic strategies should be considered.

Keywords: Breast cancer; Hypercellular variant; Hypocellular variant; Mucinous breast carcinoma; Subclassification.

Figure 1

Correlation between the mucinous carcinoma phenotype and disease-free survival in the breast cancer series. The mixed mucinous breast carcinoma patients experienced significantly poorer outcomes in all breast cancers (a) and mucinous carcinomas (b). (NS; not significant).

Figure 2

Histological findings (H.E. stain x 400). (a) primary lesion of mixed mucinous breast carcinoma. (b) metastatic lymph node of mixed mucinous breast carcinoma. (c) primary lesion of pure mucinous breast carcinoma type A. (d) metastatic lymph node of pure mucinous breast carcinoma type A.