Background. Among many oncologists the opinion exists, that multitumor breast cancer (MBC) shows greater
metastatic dynamics and has worse prognosis comparing to unitumor breast cancer (UBC) in the same TNM stage.
Some researchers think that proper evaluation of pT in MBC should be based on combined diameters and not on the
largest tumor diameter. The aim of the work is estimation of the treatment results for multiple tumors in breast cancer.

Material and methods. The retrospective analysis included 954 consecutive women with breast cancer in stage
IA-IIIC after radical mastectomy who were treated between 1995 and 1998 at the Cancer Center-Institute in Warsaw.
MBC was diagnosed after mastectomy in 104 (10.9%) of patients.
There were no significant differences in characteristics between unicentric and multicentric breast cancer groups
according to age, stage, pT, pN, type and grade of histology and methods of adjuvant treatment. Cox’s regression model was used to analyse the prognostic factors having influence on disease-free survival (DFS) and overall survival (OS). Median of follow-up was 11 years.

Results. There were no significant differences in characteristics between UBC and MBC groups according to age, stage, pT, pN, type and grade of histology and methods of adjuvant treatment. The 10-year actuarial DFS and OS and cumulative rate of locoregional recurrence for patients with UBC and MBC were 51% vs 58% p = 0.1 and 62% vs 72% p = 0.05 and 13% vs 9% p = 0.3

There were no statistical significant differences in frequencies of lymph node metastases among groups with UBC and MBC according to pT, measured as the greatest diameter of tumor. In multivariate logistic regression analyses the following classical prognostic factors had an independent influence on DFS and OS: pN, pT, G, and vascular invasion. MBC did not appeared to be a significant prognostic factor either for DFS or OS.

Conclusions. From the present retrospective analysis the results show that MBC does not reduce prognosis compared to UBC and the largest tumor rather than combined diameters of lesions should be used to establish pT.