Response of mucinous breast carcinoma to neoadjuvant chemotherapy.

Background/aim: Mucinous breast carcinoma (MBC) is thought to be a favorable-differentiated form of invasive breast cancer and is rarely preferred for neoadjuvant chemotherapy (NAC). The study aimed to define the response of MBCs to NAC.

Materials and methods: A review was made of the demographic, clinicopathologic characteristics, management and follow-up data of 70 patients diagnosed with MBC between May 2010 and December 2020 by examining the patients' historical files and oncology records.

Results: The median age, tumor size, and follow-up period of patients were 52.9 (range: 32-87) years, 25.8 (range: 8-88) mm, and 61.5 (range: 18-143) months, respectively. Of the 70 patients, 45 had conservative surgery, 25 had a mastectomy, and 22 had axillary clearance due to a positive sentinel node biopsy or clinical axilla. Eight patients (11.4%) received NAC. Twenty-one patients (30.0%) received adjuvant chemotherapy, whereas almost all the patients received hormone therapy. The preoperative core biopsy diagnosis of four of eight patients receiving NAC was unspecified invasive breast carcinoma. NAC was used as treatment in patients who were younger, had tumors larger in diameter, had tumors with an initial higher T-stage, and especially those with clinically positive axilla, and tumors with a higher Ki-67 index. Despite these preference criteria, both the overall mastectomy and axillary clearance rates were significantly higher in these patients. Two local and five systemic recurrences were observed in the follow-up period. NAC had no significant contribution to survival.

Conclusion: It may be concluded that NAC is not sufficiently effective in either helping to diminish the need for mastectomy by downsizing the tumor, or in preventing axillary clearance in MBCs, and no significant benefit on survival could be observed. In addition, the results may emphasize the importance of identifying the MBC subtype, and the significant association between the degree of response to NAC and the subtype.