Ancillary Prognostic and Predictive Testing in Breast Cancer: Focus on Discordant, Unusual, and Borderline Results

Relationship of Tubule Formation, Indian File Pattern and Apocrine Change With Estrogen and Progesterone Receptors and HER2 Immunostaining

Objectives: In breast carcinomas, histomorphological features like low-grade and lobular differentiation are associated with estrogen receptor (ER) and progesterone receptor (PR) expression. Apocrine carcinoma is associated with human epidermal growth factor receptor 2 (HER2) positivity. Studies have not emphasized the association between other histological features like tubule formation, Indian file pattern and apocrine change (which may be found in all grades of tumors or as a part of a mixed pattern of no special type) and immunohistochemistry (IHC). The study was designed to find the association between these morphological factors and ER, PR and HER2 status.

Materials and methods: The presence or absence of tubule formation, Indian file pattern and apocrine change was correlated with ER, PR and HER2 expression in core biopsies of 102 invasive breast carcinomas.

Statistical analysis: Fisher exact test with median unbiased odds ratio was used.

Results: Tubule formation and/or Indian file pattern were significantly associated with ER in all tumors (P-value <0.001), as well as separately for grade II, grade III, HER2-negative and HER2-positive tumors. Comparable results were obtained for their association with PR. Apocrine change was significantly associated with HER2 in all tumors (P-value <0.001), as well as separately for grade III, ER-positive and ER-negative tumors.

Conclusion: These histomorphological patterns are modest predictors of IHC status in breast carcinomas, even in tumors of higher grade. Knowledge of these morphological correlates of ER, PR and HER2 in breast cancer may serve as an aid in the quality management of breast carcinoma reporting.

Prognostic and predictive parameters in breast pathology: a pathologist's primer

The pathologist's role in the breast cancer treatment team has evolved from rendering a diagnosis of breast cancer, to providing a growing list of prognostic and predictive parameters such that individualized treatment decisions can be made based on likelihood of benefit from additional treatments and potential benefit from specific therapies. In all stages, ER and HER2 status help segregate breast cancers into treatment groups with similar outcomes and treatment response rates, however, traditional pathologic parameters such as favorable histologic subtype, size, lymph node status, and Nottingham grade also have remained clinically relevant in early stage disease decision-making. This is especially true for the most common subtype of breast cancer; ER positive, HER2 negative disease. For this same group of breast cancers, an ever-expanding list of gene-expression panels also can provide prediction and prognostication about potential chemotherapy benefit beyond standard endocrine therapies, with the 21-gene Recurrence Score, currently the only prospectively validated predictive test for this purpose. In the more aggressive ER-negative cancer subtypes, response to neoadjuvant therapy and` the extent of tumor infiltrating lymphocytes (TILs) are more recently recognized powerful prognostic parameters, and clinical guidelines now offer additional treatment options for those high-risk patients with residual cancer after standard neoadjuvant therapy. In stage four disease, predictive tests like germline BRCA status, tumor PIK3CA mutation status (in ER+ metastatic disease) and PDL-1 status (in triple negative metastatic disease) are now used to determine additional new treatment options. The objective of this review is to describe the latest in prognostic and predictive parameters in breast cancer as they are relevant to standard pathology reporting and how they are used in breast cancer clinical treatment decisions.

Clinical validation of Ki67 by quantitative reverse transcription-polymerase chain reaction (RT-PCR) in HR+/HER2- early breast cancer

Objective: To evaluate the clinical value of Ki67 by RT-PCR, we investigated the concordance of Ki67 expression by IHC and by RT-PCR, and assessed their prognostic value in HR+/HER2- early breast cancer.

Methods: 1259 HR+/HER2- early breast cancer patients treated at Ruijin Hospital with recurrence score were retrospectively recruited. RT-PCR assay measurement of Ki67 was conducted by 21-gene expression assay and compared with IHC measurement of Ki67 using chi-square tests. X-tile program was used to determine the optimal cutoff point for Ki67 by RT-PCR. Survival analyses were performed by Kaplan-Meier analysis and log-rank tests, and hazard ratios were derived from the Cox proportional hazards model.

Results: Ki67 by RT-PCR had a weak positive correlation with Ki67 by IHC. Pathology, grade and Ki67 expression by IHC were significantly related to the concordance between two assays, and most discordance cases were seen in patients with Ki67 ranging from 10 to 29. The estimated 3-year DFS was 96.0% in low, and 92.5% in high expression group of Ki67 by IHC, 97.0% in low and 90.4% in high expression group of Ki67 by RT-PCR. Univariate and multivariate analysis in the whole population indicated that only Ki67 by RT-PCR—but not intrinsic subtype or recurrence score—was an independent factor for DFS.

Conclusions: Ki67 assessed by RT-PCR assay was weakly correlated to Ki67 by IHC. Using 5.68 as cutoff point, Ki67 by RT-PCR had shown potential as a prognostic biomarker in HR+/HER2- early breast cancer.