Correlation of Clinicopathologic Parameters and Immunohistochemical Features of Triple-negative Invasive Lobular Carcinoma

Abstract

Invasive lobular carcinoma (ILC) is a subtype of invasive breast carcinoma. With the advent of gene profiling, breast cancer has been classified into luminal A, luminal B, HER2-overexpressing, and triple-negative carcinoma (TNC). Several studies have described TNC (ER, PR, HER2) as a surrogate for basal-like breast carcinoma. However, there is sparse literature on triple-negative lobular carcinoma (TNLC), as most of them show hormone receptor expression. The aim of this study was to investigate the correlation of clinicopathologic parameters of TNLC that has been demonstrated in invasive ductal carcinoma. Clinicopathologic parameters and immunohistochemical stains for ER, PR, E-cadherin, HER2, MIB1, and fluorescent in situ hybridization for HER2 of 255 ILC cases were retrieved. In addition, immunohistochemical analysis was performed for p53, c-kit, vimentin, p16, cyclinD1, and BCL2 on 78 cases where 12 were TNC cases and 66 were non-TNC cases. Of the 255 ILC cases, 218 (85.5%) were classic and 37 (14.5%) were pleomorphic. Seventy-seven (30.1%) cases showed axillary lymph node metastasis. There were 14 of the 255 TNC cases (5.49%) that showed higher incidence in the elderly patients. Six of the 37 (16.21%) cases were pleomorphic and 8 of the 218 (3.7%) cases were classic. Positivity for vimentin was seen in 8 of the 12 cases (67.7%), CK 5 in 3 of the 12 (25%) cases, p16 in 11 of the 12 (91.6%) cases, p53 in 8 of the 12 (66.7%) cases, c-kit in 6 of the 12 (50%) cases, and cyclinD1 in 6 of the 12 cases (50%) indicating basal-like phenotype in 3 cases and nonbasal-like phenotype in 9 cases. There was no statistical significance in lymph node metastasis, tumor recurrence, and distant metastasis between TNC and non-TNC. TNLC showed distinct clinicopathologic features such as more frequently seen in the elderly, pleomorphic, larger tumor size, increased expression of vimentin, CK 5, p16, p53, and c-kit. Not all cases showed basal-like phenotype. TNLC is less frequently seen as compared with TNC in invasive ductal carcinoma.