Pure mucinous carcinomas of breast: morphologic features and prognostic correlates.

Fifty-three pure mucinous carcinomas of breast were studied, with long-term follow-up evaluation (average, 15 years) for 37. The mean age of the patients was 63 years. Long-term survival (Kaplan-Meier method) was 68 per cent, excluding non-tumor-related deaths. Median survival for the patients with fatal carcinomas was 11.3 years. Fatal and disseminated carcinomas were best predicted by the presence of axillary metastases and by tumor cellularity and size. Only five of the patients had axillary metastases at mastectomy, but in four of these five patients distant metastases developed later. The diameters of all ten of the fatal and disseminated carcinomas were at least 2.5 cm, while 17 of the 27 long-term survivors had smaller tumors. All ten of the fatal and disseminated carcinomas had cellularity of more than 10 per cent, while 12 of 27 long-term survivors had less cellular tumors. Tumor cellularity did not correlate with tumor size; these features were entirely independent. Thus, in contrast to the findings of some prior studies with shorter follow-up periods, pure mucinous carcinomas were seen to be slowly growing, but fully malignant, tumors warranting standard breast carcinoma treatment.