Cytologic features of triple-negative breast carcinoma

Triple-negative breast cancer (TNBC) is distinct from other breast cancers, because the tumor cells lack estrogen and progesterone receptors (hormone receptors) and also are negative for human epidermal growth factor receptor 2 (HER2). They comprise a heterogeneous group of tumors with various histologic features and clinical behaviors. High-grade, invasive ductal carcinoma not otherwise specified is the most frequent type, and a substantial fraction of TNBCs belongs to the basal-like tumor type. The purpose of this study was to determine whether some cytologic features could predict the triple phenotype of breast carcinoma.

Fine-needle aspiration cytology samples of 62 TNBCs were compared with samples of 82 hormone receptor-positive, high-grade, invasive carcinomas (HRBC) and with samples of 33 hormone receptor-negative, HER2 positive, invasive carcinomas (HER2BC) for the following cytomorphologic features: cellularity, necrosis, lymphocytes, syncytial clusters, tubular/ductal-like clusters, large bare nuclei, streaming within the clusters, and calcifications. Moreover, single cell features, such as cellular borders, cytoplasm, cytoplasmic vacuoles, nuclear pleomorphism, nucleoli, and type of chromatin pattern, were evaluated. Descriptive analyses and 2 multivariate regression models were performed to compare TNBC, HRBC, and HER2BC and to identify the cytologic factors that were associated with tumor type.

TNBCs were more likely to have an abundant necrotic background, many lymphocytes, many syncytial clusters, and ill defined cell borders than non-TNBCs. A tubular/ductal pattern was observed only rarely in TNBCs. Multivariate logistic analysis indicated a 90.8% probability of identifying TNBC versus HRBC by the following cytologic variables: lymphocytes, ill defined cell borders and syncytial clusters, tubular/ductal clusters, cytoplasmic vacuoles, and cellular pleomorphism; whereas there was a 77.5% probability of identifying TNBC rather than HER2BC by the following variables: cellularity, ill defined cellular borders and syncytial clusters, and tubular/ductal clusters.

Although TNBCs embrace a heterogeneous group of tumors, in this study, they exhibited some common cytologic features that can help to distinguish them from other high-grade breast carcinomas in daily practice.