Concordance of HER2 status assessed on needle core biopsy and surgical specimens of invasive carcinoma of the breast.

AIMS: Human epidermal growth factor receptor 2 (HER2) status of invasive breast cancers is vital for selection of patients for trastuzumab treatment. This study aimed to assess the level of agreement of HER2 status in core biopsy and excision specimens using immunohistochemistry, with in-situ hybridisation for equivocal cases. METHODS AND RESULTS: 300 consecutive invasive carcinomas with core biopsy and surgical specimens had HER2 assessed on both specimens. Immunohistochemistry was performed first. Fluorescence in-situ hybridization (FISH) was automatically performed if the immunohistochemistry was scored as equivocal (2+). There was agreement between the HER2 status of the two specimens in 294 tumours (98%). In two carcinomas the core was negative and the excision specimen showed focal strong staining with amplification. In four carcinomas the core biopsy was negative and the excision showed 2+ staining with amplification in at least one block (although in three there was no amplification in a second block). CONCLUSION: There is excellent agreement between HER2 assessed in core biopsy and surgical specimens. Discrepancies arise most frequently due to focal amplification or levels of gene amplification around the cut-off for defining positivity.

Minichromosome maintenance protein 2 is a strong independent prognostic marker in breast cancer.

PURPOSE: To test the hypothesis that prognostic information in breast cancer may be derived from an accurate assessment of epithelial cell cycle entry, as indicated by expression of minichromosome maintenance (MCM) proteins. MATERIALS AND METHODS: We used immunohistochemistry to examine the distribution of Mcm-2 in breast tissue. Power calculations based on a pilot study of 67 whole tissue sections led to selection of an independent 347-core breast carcinoma tissue microarray validation set. We tested for associations between Mcm-2 (and Ki-67) labeling index (LI) and various clinicopathologic parameters. RESULTS: Mcm-2 was expressed more frequently than the standard proliferation marker Ki-67 in whole tissue sections of normal breast (P =.0003) and breast carcinoma (P <.0001). In 221 assessable cores of invasive carcinoma, the Mcm-2 LI showed a positive association with tumor size (P =.002), mitotic index (P <.0001), histologic grade (P <.0001), and the Nottingham Prognostic Index (NPI) score (P <.0001). Using a cutoff value of 50%, Mcm-2 LI was associated with overall survival (P =.0007), disease-free interval (P =.0002), and with the development of regional recurrence (P =.011) and distant metastases (P =.0016). Cox regression analysis suggested that the Mcm-2 LI is a strong prognostic factor in breast cancer that is independent and superior to histologic grade, lymph node stage, and Ki-67 LI, but not the NPI score. CONCLUSION: Mcm-2 may be of utility as a prognostic marker to refine the prediction of outcome in breast cancer, for example when combined with parameters currently used in the NPI.

An immunohistochemical study of metaplastic spindle cell carcinoma, phyllodes tumor and fibromatosis of the breast.

The diagnosis of metaplastic (sarcomatoid) carcinoma (MSC) of breast often requires immunohistochemistry with a cytokeratin (CK) panel to distinguish them from phyllodes tumors (PT), primary sarcomas, and fibromatoses. CK staining may be heterogeneous in metaplastic carcinomas. The aim of the study was to investigate the theory that MSCs show evidence of myoepithelial differentiation and to evaluate immunohistochemical markers that may be helpful in distinguishing MSCs from PT and fibromatosis. We reviewed histology and performed immunohistochemistry for AE1/AE3, 34betaE12, CK5 and CK14, Cam5.2, CK7 and CK19, epithelial membrane antigen (EMA) (B55), smooth muscle actin (SMA), S100, desmin, vimentin, CD31, CD34, and bcl-2 on paraffin-embedded tissue from 18 MSCs, 26 PTs, and 8 fibromatoses. We assessed staining by using a semiquantitative method. Sarcomatous areas in MSCs were positive for 34betaE12 in 11 cases; for SMA in 10; for CK5 in 7; for CK14 in 6; for Cam5.2, AE1/AE3, and S100 in 5; and for CK7 and CK19 in 3. No CK expression was seen in stromal areas in PT or in fibromatoses. CD34 and bcl-2 were more frequently expressed in spindle cell areas in PTs (18 and 12 of 26, respectively) than in MSCs (0 and 2 of 18, respectively). MSCs show strong evidence of myoepithelial differentiation. CD34 and, to a lesser extent, bcl-2 positivity in PTs may be helpful in differentiating these two lesions from MSCs, particularly in small biopsies, because CK staining in MSCs may be heterogeneous. In our hands, 34betaE12 was the CK most frequently expressed in sarcomatoid areas in MSCs.

The effect of delay in fixation on HER2 expression in invasive carcinoma of the breast assessed with immunohistochemistry and in situ hybridisation.

AIMS: Accurate assessment of HER2 status is essential for selection of patients for HER2-targeted treatment such as trastuzumab. This study investigated the hypothesis that delayed fixation impairs HER2 assessment. METHODS: 9 carcinomas were received fresh, and samples were fixed immediately or put in fixative at time intervals up to 24 h. All carcinomas were scored as 3+ with immunohistochemistry in properly fixed tissue. RESULTS: 2 of 9 carcinomas (95% CIs 6% to 56%) showed reduced immunohistochemical staining with delays in fixation of 1 and 8 h. One carcinoma showed low-level amplification with fluorescence in situ hybridisation (FISH) when properly fixed and was not amplified after delayed fixation. The other carcinomas were amplified at all time points. CONCLUSIONS: Delayed fixation impaired HER2 protein expression assessed using immunohistochemistry in 22% of 3+ carcinomas. HER2 amplification assessed using FISH may be less affected.

Breast carcinomas with borderline (2+) HER2 immunohistochemistry: percentage of cells with complete membrane staining for HER2 and the frequency of HER2 amplification.

AIM: HER2 status is vital for selecting breast cancer patients for trastuzumab treatment. One recommended approach is to assess immunohistochemical staining and then perform in situ hybridisation on those tumours with a borderline (2+) immunohistochemical result. This audit aimed to assess the value of the percentage of immunohistochemical staining in 2+ tumours in selecting tumours for in-situ hybridisation. METHODS: HER2 immunohistochemistry and in situ hybridisation was performed according to UK guidelines. The percentage of complete membrane staining of invasive carcinoma cells for HER2 was recorded as part of routine reporting. RESULTS: 191 (11%) of 1735 invasive carcinomas were scored as 3+. 419 (24%) were scored as 2+. 57 of 413 2+ carcinomas (14%) were amplified (ratio of HER2 to chromosome 17 ≥ 2.0). The frequency of amplification was related to the percentage of complete membrane staining: eight of 149 (5%) with 10-19% membrane staining, 11 of 93 (12%) with 20-29% staining, 26 of 150 (17%) with 30-79% staining and 12 of 21 (57%) with 80-100% staining. CONCLUSIONS: This audit suggests that increasing the threshold for 2+ from 10% to 20% complete membrane staining would reduce the number of in-situ hybridisation tests by 36%, but reduce the detection of amplified tumours by 14%.