Expression of E-cadherin, alpha-catenin, and beta-catenin in tubulolobular carcinoma of the breast.

Tubulolobular carcinoma (TLC) of the breast is a rare subtype of breast carcinoma categorized by Fisher et al. (Hum Pathol 8:679-683, 1977) as a tubular variant of lobular carcinoma. E-cadherin is a transmembrane glycoprotein, and complete loss of E-cadherin expression has been observed in invasive lobular carcinoma. Ductal carcinoma retains at least some expression of E-cadherin. Moreover, the adhesive function of E-cadherin is dependent on the integrity of the catenin components, which link E-cadherin to the actin filaments. In order to achieve improved categorization of TLC, we decided to investigate both E-cadherin and the catenins in TLCs and invasive lobular carcinomas. We reviewed all 1,430 cases of primary breast carcinoma that were surgically resected at Saitama Medical Center, Saitama Medical School, and at Saitama Red Cross Hospital between 1990 and 2005. Among these, 16 cases of TLC were reported retrospectively. The results were compared with those of 20 cases of invasive lobular carcinomas that were included as controls. Tumor tissue was immunostained for E-cadherin, alpha-catenin, and beta-catenin. The presence of immunoreactivity in the TLC was seen in 12 (75%) cases for E-cadherin, in 8 (50%) cases for alpha-catenin, and in 10 (62.5%) cases for beta-catenin. However, plasma-membrane-associated staining for E-cadherin, alpha-catenin, and beta-catenin was completely absent in invasive lobular carcinomas. These results suggest the possibility that TLCs are not a variant of lobular carcinoma, but rather ductal carcinomas with a lobular growth pattern.