Huge mucinous carcinoma of the breast in which doubling time was observed by computed tomography during 3 years without treatment.

Here we report the case of a 77-year-old woman with a huge cancer of the right breast for which size was measured on computed tomography in our hospital preoperatively and in other hospital 3 years earlier. During the 3-year untreated interval, the tumor grew from 4 cm to 13 cm in maximum diameter, and the tumor-volume doubling time (TVDT) was calculated as 209 days. The patient underwent mastectomy with axillary lymph node dissection, with the large skin defect covered by autologous skin graft. The pathological diagnosis was pure mucinous carcinoma (MC) of the breast with a low MIB-1 index, no vessel invasion, and no lymph node metastasis. Breast MC has been known to show a slow growth rate, but the TVDT of this current tumor was not markedly different from that of common breast cancers described in previous reports. This short TVDT notwithstanding the low aggressiveness may be due to abundant mucin occupying the majority of the tumor volume. To the best of our knowledge, no previous reports have provided accurate TVDTs for breast MC.