Calretinin expression in high-grade invasive ductal carcinoma of the breast is associated with basal-like subtype and unfavorable prognosis

Abstract

Calretinin, a calcium-binding protein, is a widely used marker for mesothelial differentiation. There is accumulating evidence of calretinin expression in epithelial and mesenchymal malignancies, as well. The objectives of this study were to (1) further delineate the expression of calretinin in grade 3 breast carcinomas in the context of molecular subtypes and (2) identify the impact of calretinin expression on overall and disease-free survival. On the basis of immunohistochemical expression of estrogen receptor, progesterone receptor, human epidermal growth factor receptor-2 (HER2), cytokeratin 5/6, and epidermal growth factor receptor, 214 grade 3 invasive ductal carcinomas were stratified into 36 luminal A, 63 luminal B, 24 HER2 positive, 81 basal-like (including 13 metaplastic carcinomas), and 10 unclassified. Tissue microarrays were analyzed for immunohistochemical expression of calretinin. High-level calretinin expression was identified in a significant proportion of basal-like (54.3%), HER2 (33.3%), and unclassified (30%) tumors. In contrast, luminal A and B subtypes demonstrated high-level calretinin expression in only 11.1% and 12.7%, respectively (P < .0001). Within the basal-like group, 38.5% of the metaplastic carcinomas demonstrated high-level expression, associated predominantly with the epithelial component and squamous metaplasia. High-level calretinin expression was strongly associated with decreased overall survival in the entire cohort of grade 3 cancer (P = .0096) and in the basal-like group (P = .039). Multivariate analysis revealed that both tumor stage and high-level calretinin expression were independent predictors of overall survival (P = .0002 and P = .0023, respectively). In conclusion, high-level calretinin expression is most common in grade 3 tumors with a basal-like phenotype and is associated with poor overall survival.

Keywords: Basal-like; Breast; Calretinin; Carcinoma; Immunohistochemisty.

Figure 1

Calretinin expression in non-neoplastic and malignant breast tissue. Non-neoplastic breast tissue is negative for calretinin staining (A, ×200). Strong nuclear and cytoplasmic immunoreactivity in basal-like breast carcinoma (B, ×400). Strong nuclear and cytoplasmic calretinin immunostaining in squamous component of metaplastic carcinoma. Note intercellular bridges indicative of squamous differentiation (C, ×400). Weak focal calretinin immunoreactivity in mesenchymal spindle cell component of metaplastic carcinoma (D, ×400).

Figure 1

Calretinin expression in non-neoplastic and malignant breast tissue. Non-neoplastic breast tissue is negative for calretinin staining (A, ×200). Strong nuclear and cytoplasmic immunoreactivity in basal-like breast carcinoma (B, ×400). Strong nuclear and cytoplasmic calretinin immunostaining in squamous component of metaplastic carcinoma. Note intercellular bridges indicative of squamous differentiation (C, ×400). Weak focal calretinin immunoreactivity in mesenchymal spindle cell component of metaplastic carcinoma (D, ×400).

Figure 1

Calretinin expression in non-neoplastic and malignant breast tissue. Non-neoplastic breast tissue is negative for calretinin staining (A, ×200). Strong nuclear and cytoplasmic immunoreactivity in basal-like breast carcinoma (B, ×400). Strong nuclear and cytoplasmic calretinin immunostaining in squamous component of metaplastic carcinoma. Note intercellular bridges indicative of squamous differentiation (C, ×400). Weak focal calretinin immunoreactivity in mesenchymal spindle cell component of metaplastic carcinoma (D, ×400).

Figure 1

Calretinin expression in non-neoplastic and malignant breast tissue. Non-neoplastic breast tissue is negative for calretinin staining (A, ×200). Strong nuclear and cytoplasmic immunoreactivity in basal-like breast carcinoma (B, ×400). Strong nuclear and cytoplasmic calretinin immunostaining in squamous component of metaplastic carcinoma. Note intercellular bridges indicative of squamous differentiation (C, ×400). Weak focal calretinin immunoreactivity in mesenchymal spindle cell component of metaplastic carcinoma (D, ×400).

Figure 2

Hierarchical clustering analysis (Complete method with data standardization) of the expression of calretinin, estrogen receptor (ER), progesterone receptor (PR), HER2, CK5/6, and epidermal growth factor receptor (EGFR) in grade 3 carcinoma. Each column represents a different tumor, and each row a marker. Red: highest expression; blue: lowest expression. The analysis shows that calretinin-high cases are clustered predominantly with cases positive for basal markers CK5/6 and EGFR, as indicated by short dendrogram branches linking these markers. Calretinin-low cases are clustered with ER and PR positive tumors.

Figure 3

Analysis of overall survival in grade 3 invasive ductal carcinoma by stage (A), calretinin expression (high vs low) in the entire cohort (B), and calretinin expression (high vs low) in basal-like subtype only (C).

Figure 3

Analysis of overall survival in grade 3 invasive ductal carcinoma by stage (A), calretinin expression (high vs low) in the entire cohort (B), and calretinin expression (high vs low) in basal-like subtype only (C).

Figure 3

Analysis of overall survival in grade 3 invasive ductal carcinoma by stage (A), calretinin expression (high vs low) in the entire cohort (B), and calretinin expression (high vs low) in basal-like subtype only (C).