Intertumoral heterogeneity of bifocal breast cancer: a morphological and molecular study

PURPOSE

To analyze concordance rates between individual foci of bifocal BC for histological grade, type and intrinsic subtype based on immunohistochemical (IHC) and mRNA-testing using MammaTyper.

METHODS

We evaluated histological grade and type as well as intrinsic subtype based on IHC status for estrogen and progesterone receptors, HER2 and the mitotic activity index in 158 individual foci of 79 bifocal BC. A subgroup of 31 cases additionally underwent mRNA-based subtyping using the MammaTyper (MT) test. We calculated concordance rates between individual foci, as well as Cohen's Kappa (K).

RESULTS

For 79 bifocal BC, concordance rates between individual foci for grade, histological type, and IHC-based subtype were 69.6% (K=0.53), 92.4% (K=0.81), and 74.7% (K=0.62), respectively. In the MT subgroup of 31 bifocal BC, concordance rates between individual foci for grade, histological type, IHC-based and mRNA-based intrinsic subtype were 87.1% (K=0.78), 90.3% (K=0.73), 87.1% (K=0.82), and 87.1% (K=0.7), respectively. Overall concordance between IHC- and mRNA-based subtype in the MT subgroup was 79% (K=0.7). In 6/79 cases (7.6%), testing of the smaller focus added clinically relevant information either on IHC- or mRNA-level: four cases showed high hormonal receptor expression while the expression in the larger focus was negative or low, warranting additional endocrine treatment; two cases presented with higher proliferative activity in the smaller focus, warranting additional chemotherapy.

CONCLUSION

In bifocal BC, intertumoral heterogeneity on the morphological, immunohistochemical and molecular level is common, with discordant intrinsic subtype in up to 25% between individual foci, with about 8% clinically relevant discordances.

Spontaneous expression of the gene of KI67 and P53 in cynomolgus monkeys infected with papillomavirus

Background and Aim: Cynomolgus monkeys (Macaca fascicularis) develop spontaneous infection of Papillomavirus (PV); thus, potentially beneficial for modeling human PV (HPV) infection study. Contrary to human origin, infection in cynomolgus monkeys does not always show evident clinical symptoms of cervical cancer. The absence of cervical cancer clinical symptoms leads us to investigate the molecular mechanism of the HPV infection in cynomolgus monkeys. This study aimed to investigate the messenger ribonucleic acid (mRNA) expression levels of KI67 and P53 genes, majorly known as biomarker oncogenesis of PV infection. Materials and Methods: The polymerase chain reaction (PCR) technique was used with MY11/MY09 primer to screen PV in cynomolgus monkey, further grouped as positive-PV and negative-PV infection groups. Real-time quantitative PCR was also applied to quantify the mRNA expression levels of KI67 and P53 genes in animals. Results: Increased expression of mRNA level of KI67 genes was significantly higher in Positive- PV group than negative-PV group. In contrast, the P53 mRNA expression level increased markedly higher in the negative-PV group than in the positive-PV group. Conclusion: Our study describes the potential of cynomolgus monkeys as a spontaneous oncogenesis model of PV infection-type. However, we used a limited number of cancer genetic markers. So, further study of other genetic markers is required to prove that cervical cancer could be developed naturally in cynomolgus monkeys.

Identifying ultrasound features of positive expression of Ki67 and P53 in breast cancer using radiomics

PURPOSE

To examine the relationship between ultrasonic findings and positive expression of Ki67 and P53 in breast cancer.

MATERIAL AND METHODS

Surgical resection specimens of 263 breast cancer lesions were examined. Ultrasound examination and pathological examination were performed on each lesion for retrospective analysis. We applied regression analysis to the ultrasonic features related to the positive expression of Ki67 and P53 and obtained the corresponding models. To analyze diagnostic efficiency, we calculated the area under the curve (AUC). Additionally, we created a heat map to show the results of the cluster analysis.

RESULTS

Lesions with higher Ki67 expression were associated with posterior acoustic enhancement, absence of an echo halo and a higher Breast Imaging Reporting and Data System (BI-RADS) category. P53-positive cancer were associated with an absence of an echo halo and a higher BI-RADS category. The AUC of the regression models of Ki67 and P53 was 0.78 and 0.71, respectively.

CONCLUSIONS

Our study revealed that breast cancer ultrasonic findings were closely related to expression of molecular indicators, suggesting that ultrasound can be used to provide useful information to clinicians.

Luminal A versus luminal B breast cancer: MammaTyper mRNA versus immunohistochemical subtyping with an emphasis on standardised Ki67 labelling-based or mitotic activity index-based proliferation assessment

AIMS

Proliferation assessment by the use of Ki67 is a crucial component in intrinsic subtyping of luminal breast cancers (BCs), but suffers from variability between laboratories, observers, and methods. MammaTyper is a quantitative molecular tool that measures mRNA levels of ERBB2, ESR1, PGR and MKI67 in BC, and interprets the results according to the St Gallen 2013 consensus recommendations. We compared MammaTyper with immunohistochemistry (IHC)-based subtypes, with a focus on standardised proliferation assessment.

METHODS AND RESULTS

We analysed the agreement in assigning subtypes between MammaTyper and receptor IHC in 101 unifocal luminal HER2-negative early BCs of no special type. Two Ki67 counting protocols, Ki67-Global (Ki67-G) and Ki67-HotSpot (Ki67-H), recommended by the International Ki67 in BC Working Group, and the mitotic activity index (MAI) were used for proliferation assessment. The proportions of BCs identified as luminal A and as luminal B were 55% and 45% for MammaTyper, 55% and 45% for IHC + Ki67-G, 36% and 64% for IHC + Ki67-H, and 56% and 44% for IHC + MAI. The levels of agreement between MammaTyper-based and IHC-based subtyping were 84% (κ = 0.679) for IHC + Ki67-G, 72% (κ = 0.462) for IHC + Ki67-H, and 89% (κ = 0.779) for IHC + MAI.

CONCLUSIONS

High rates of agreement between mRNA-based and IHC-based intrinsic subtyping of luminal HER2-negative BC can be achieved. However, the agreement between IHC-based and MammaTyper-based luminal subtypes depends on the proliferation assessment method, and was highest when the MAI was used. Further comparative clinical studies are needed to determine which method is to be preferred, including analysis of cost-effectiveness.

Performance of 4 Immunohistochemical Phosphohistone H3 Antibodies for Marking Mitotic Figures in Breast Cancer

BACKGROUND

Phosphohistone H3 (PHH3) has been suggested to facilitate and improve mitotic activity assessment in breast cancer and other tumor entities, but the reliability of respective immunohistochemical antibodies has not yet been compared for routine purposes. Our aim was to test the performance of 4 different PHH3 antibodies on a series of highly proliferating breast cancers with good preservation of morphology.

METHODS

Four commercially available PHH3 antibodies were tested on 9 grade 3 invasive breast cancers processed in the same batch. We analyzed the number of antibody stained and nonstained mitotic figures as well as the total of cells observed in 10 high power fields per tumor to calculate sensitivity, specificity, and accuracy of the respective antibodies for staining mitotic figures, taking morphologically defined mitotic figures as gold standard.

RESULTS

Sensitivity, specificity, and accuracy of the respective PHH3 antibodies for staining mitotic figures were 54.51%, 99.98%, and 98.79% for Cell Marque, 87.48%, 67.62%, and 67.47% for Epitomics, 98.62%, 99.73%, and 99.49% for Merck 06-570, and 99.74%, 99.52%, and 99.51% for Merck 09-797, respectively. Sensitivity was lowest for telophase. In statistical analysis, the Cell Marque antibody demonstrated significantly lower sensitivity and Epitomics substantially lower sensitivity and specificity than Merck 06-570 and Merck 09-797 antibodies (P<0.0001, respectively).

CONCLUSIONS

Performance and reliability varied significantly between the 4 tested antibodies. For faster identification of mitotic hot spots and as potential marker in digital image analysis, the Merck antibodies seem to be most suitable.

Interlaboratory variability of Ki67 staining in breast cancer

BACKGROUND

Postanalytic issues of Ki67 assessment in breast cancers like counting method standardisation and interrater bias have been subject of various studies, but little is known about analytic variability of Ki67 staining between pathology labs. Our aim was to study interlaboratory variability of Ki67 staining in breast cancer using tissue microarrays (TMAs) and central assessment to minimise preanalytic and postanalytic influences.

METHODS

Thirty European pathology labs stained serial slides of a TMA set of breast cancer tissues with Ki67 according to their routine in-house protocol. The Ki67-labelling index (Ki67-LI) of 70 matched samples was centrally assessed by one observer who counted all cancer cells per sample. We then tested for differences between the labs in Ki67-LI medians by analysing variance on ranks and in proportions of tumours classified as luminal A after dichotomising oestrogen receptor-positive cancers into cancers showing low (<14%, luminal A) and high (≥14%, luminal B HER2 negative) Ki67-LI using Cochran's Q.

RESULTS

Substantial differences between the 30 labs were indicated for median Ki67-LI (0.65%-33.0%, p < 0.0001) and proportion of cancers classified as luminal A (17%-57%, p < 0.0001). The differences remained significant when labs using the same antibody (MIB-1, SP6, or 30-9) were analysed separately or labs without prior participation in external quality assurance programs were excluded (p < 0.0001, respectively).

CONCLUSION

Substantial variability in Ki67 staining of breast cancer tissue was found between 30 routine pathology labs. Clinical use of the Ki67-LI for therapeutic decisions should be considered only fully aware of lab-specific reference values.

St Gallen 2015 subtyping of luminal breast cancers: impact of different Ki67-based proliferation assessment methods

Ki67 has been proposed as prognostic proliferation marker in luminal breast cancer (BC), but little is known on the influence of Ki67 assessment methods on subtyping into luminal A- and B-like tumors. Our aim was to study the influence of different Ki67-labeling index (Ki67-LI) assessment methods on the proportion of BCs classified as luminal A-like. 280 early BCs were subtyped according to the St Gallen 2015 definitions into 71 % luminal (HER2 negative), 6 % luminal B-like (HER2 positive), 13 % triple negative, 1 % HER2 positive (nonluminal), and 9 % special type. Digitized whole slides were counted manually on the screen. We used nine defined counting methods to assess the Ki67-LI (including the International Ki67 in Breast Cancer Working Group recommendations), and compared the resulting medians and the proportions of cancers classified as luminal A-like according to the formerly used cut-off <20 %. Methods assessing hot spots and tumor periphery resulted in significantly higher Ki67-LI medians than those measuring an average proliferation (27.45 % vs 16.96 %, p < 0.0001). Substantially lower median Ki67-LI were found when assessing 1020 compared to counting 100, 200, 300 cells (17.65 vs 33 %, vs 28 %, vs 24.33 %, respectively; p < 0.0001), or 510 cells (20.59 %, p = 0.019). Applying a standard Ki67-LI cut-off <20 % to define low proliferation for all methods, the proportion of luminal A-like cancers varied between 13 and 44 %. The proportion of BCs classified as luminal A-like is highly influenced by the Ki67-LI assessment method. As a consequence, the selection of a specific Ki67-LI assessment method may have a direct effect on the proportion of patients considered having low-risk disease and thus influence therapeutic decision making. This calls for a standardized assessment method.

Prognostic impact of discrepant Ki67 and mitotic index on hormone receptor-positive, HER2-negative breast carcinoma

Background:

Inconsistencies between mitotic index (MI) and Ki67 measures have been identified in many breast tumour samples. The aim of this study was to describe the prognosis of hormone receptor-positive (HR+) HER2− tumours having discrepant MI and Ki67.

Methods:

We included a cohort of breast cancer patients initially treated by surgery between 2001 and 2005 in the Institut Curie. Breast cancer-specific survival (BCSS) and disease-free survival (DFS) were analysed according to three proliferation groups: high MI/high Ki67 (MI=3, Ki67>20%), low MI/low Ki67 (MI<3, Ki67⩽20%) and discrepant (high MI/low Ki67 or low MI/high Ki67).

Results:

Among the 1430 patients, 19.6% had discrepant Ki67 and MI, 11.6% had high markers and 68.8% had low markers. The 5-year BCSS was 95.8%, 95% CI (0.93–0.98) in the discrepant group, 99.3%, 95% CI (0.993–0.999) in the low-proliferation group and 91.8%, 95% CI (0.88–0.96) in the high-proliferation group. In multivariate analysis, the survival of the discrepant group was lower than that of the low-proliferation group: BCSS hazard ratio (HR)=3.01 (1.32–6.84; P=0.008) and DFS HR=2.07, 95% CI (1.31–3.26; P=0.002). Among grade 2 tumours in multivariate analysis, DFS of the discrepant group was lower than that of the low MI/low Ki67 group: HR=1.98, 95% CI (1.14–3.46), P=0.02. Regarding BCSS, the obtained results were similar.

Conclusion:

The prognosis of patients with discrepant MI and Ki67 appears intermediate between that of low MI/low Ki67 and high MI/high Ki67 groups. These markers should be jointly analysed to clarify prognosis.

Prognostic impact of the inclusion of uPA/PAI-1 tumor levels in the current adjuvant treatment decision-making for early breast cancer

AIMS

Following the introduction of new adjuvant therapies we wanted to reappraise the prognostic and predictive value of uPA/PAI-1 in early breast cancer.

PATIENTS & METHODS

This monocentric retrospective study included 652 patients who had curative surgery between 2006 and 2011 and adjuvant treatment decision-making, taking into account uPA/PAI-1 tumor levels.

RESULTS

uPA and PAI-1 levels were associated with classical clinicopathological parameters and adjuvant chemotherapy decision, but not with peritumoral vascular invasion (PVI; also known as peritumoral vascular emboli). HER2 overexpression, PVI and uPA/PAI-1 levels were not significantly associated with relapse-free survival in univariate analysis. In multivariate analysis, T stage, N stage and progesterone receptors were the only independent relapse-free survival predictive factors.

CONCLUSION

The absence of an association between uPA/PAI-1 and PVI allows their concomitant consideration in adjuvant treatment discussion. The overall good prognosis of patients with high uPA/PAI-1 levels might be linked to the uPA/PAI-1 predictive value and the inclusion of these parameters in adjuvant guidelines.

Detection of circulating cytokeratin-19 mRNA-positive cells in the blood and the mitotic index of the primary tumor have independent prognostic value in early breast cancer

BACKGROUND

Previous studies showed that molecular detection of CK-19 mRNA in peripheral blood and the mitotic index of primary tumors have prognostic value in early breast cancer. The aim of this study was to assess the association between these variables.

PATIENTS AND METHODS

The primary tumors of 223 operable breast cancer patients (92 premenopausal and 131 postmenopausal) were evaluated for the MAI classified as either ≤ 5 per 10, 6 to 10 per 10 and > 10 per 10 or < 10 per 10 and ≥ 10 per 10 mitoses per high power field using a standardized protocol previously reported. Peripheral blood was also collected before and after the end of adjuvant chemotherapy for detection of CK-19 mRNA-positive cells using reverse transcription polymerase chain reaction previously described.

RESULTS

After a median follow-up of 118 months, 75 patients (33.6%) experienced disease relapse and 56 (25.1%) died of breast cancer. MAI was strongly associated with disease-free survival (DFS) and overall survival (OS) (P < .001 for DFS and OS together). Detecting CK-19 mRNA-positive cells in the peripheral blood before but not after adjuvant chemotherapy was associated with marginally worse DFS (P = .055) and OS (P = .059). Cox regression analysis revealed that MAI and CK-19 mRNA-positive cell detection before adjuvant chemotherapy were independent variables associated with decreased DFS (P < .001 and P = .038, respectively) and OS (P < .001 and P = .029, respectively). There was no significant interaction between MAI and detection of CK-19 mRNA-positive cells.

CONCLUSION

MAI of the primary tumor and detection of CK-19 mRNA-positive cells in the blood before adjuvant chemotherapy in early breast cancer patients are 2 independent prognostic factors associated with clinical outcome.

The prognostic value of mitotic activity index (MAI), phosphohistone H3 (PPH3), cyclin B1, cyclin A, and Ki67, alone and in combinations, in node-negative premenopausal breast cancer

Proliferation, either as the main common denominator in genetic profiles, or in the form of single factors such as Ki67, is recommended for clinical use especially in estrogen receptor-positive (ER) patients. However, due to high costs of genetic profiles and lack of reproducibility for Ki67, studies on other proliferation factors are warranted. The aim of the present study was to evaluate the prognostic value of the proliferation factors mitotic activity index (MAI), phosphohistone H3 (PPH3), cyclin B1, cyclin A and Ki67, alone and in combinations. In 222 consecutive premenopausal node-negative breast cancer patients (87% without adjuvant medical treatment), MAI was assessed on whole tissue sections (predefined cut-off ≥10 mitoses), and PPH3, cyclin B1, cyclin A, and Ki67 on tissue microarray (predefined cut-offs 7th decile). In univariable analysis (high versus low) the strongest prognostic proliferation factor for 10-year distant disease-free survival was MAI (Hazard Ratio (HR)=3.3, 95% Confidence Interval (CI): 1.8-6.1), followed by PPH3, cyclin A, Ki67, and cyclin B1. A combination variable, with patients with MAI and/or cyclin A high defined as high-risk, had even stronger prognostic value (HR=4.2, 95%CI: 2.2-7). When stratifying for ER-status, MAI was a significant prognostic factor in ER-positive patients only (HR=7.0, 95%CI: 3.1-16). Stratified for histological grade, MAI added prognostic value in grade 2 (HR=7.2, 95%CI: 3.1-38) and grade 1 patients. In multivariable analysis including HER2, age, adjuvant medical treatment, ER, and one proliferation factor at a time, only MAI (HR=2.7, 95%CI: 1.1-6.7), and cyclin A (HR=2.7, 95%CI: 1.2-6.0) remained independently prognostic. In conclusion this study confirms the strong prognostic value of all proliferation factors, especially MAI and cyclin A, in all patients, and more specifically in ER-positive patients, and patients with histological grade 2 and 1. Additionally, by combining two proliferation factors, an even stronger prognostic value may be found.

Adjuvant early breast cancer systemic therapies according to daily used technologies

Prognosis of early breast cancer patients is significantly improved with the use of adjuvant therapies. Various guidelines have been proposed to select patients who will derive the most benefit from such treatments. However, classifications have limited usefulness in subsets of patients such as those with node negative breast cancer. The 2007 St. Paul de Vence Clinical Practice Recommendations proposed to consider adjuvant therapy in accordance with the 10-year relapse-free survival reduction estimated by Adjuvant! Online. However, many limitations remain regarding the use of Adjuvant! Online. Among them, adverse prognostic and/or predictive factors such as vascular invasion, mitotic activity, progesterone receptor negativity, and HER-2 expression are not incorporated in the routine clinical decision process. Our group has therefore issued guidelines based on the consideration of both Adjuvant! Online calculations and the prognostic and/or predictive effects of these markers. In addition, web-accessible comprehensive tables summarizing these recommendations are provided.

In Patients Younger Than Age 55 Years With Lymph Node–Negative Breast Cancer, Proliferation by Mitotic Activity Index Is Prognostically Superior to Adjuvant!

Purpose

In breast cancer, different tools are used for prognostication and adjuvant systemic therapy selection. We compared the accuracy of the online program Adjuvant!, the Norwegian Breast Cancer Group (NBCG) guidelines, and the proliferation factor mitotic activity index (MAI) in patients with lymph node (LN) –negative disease (pN0).

Patients and Methods

Adjuvant! and MAI thresholds were set to 90% to 95% breast cancer–specific survival (BCSS) rates. These thresholds were 95% for Adjuvant!, 3 for MAI, and as follows for NBCG: pT1 grade 1 + pT1a-b grade 2 to 3; all pN0M0 and estrogen receptor/progesterone receptor positive versus all others. In 516 patients younger than age 55 years (T1-3N0M0) without adjuvant systemic therapy, univariable and multivariable 10-year BCSS rates were estimated.

Results

Median follow-up time was 118 months. The concordance between MAI and Adjuvant! or NBCG was fair (κ = 0.35 and κ = 0.29, respectively). Adjuvant!, NBCG, and MAI were all prognostically significant (P ≤ .001). In the univariable analysis, the 10-year BCSS of MAI less than 3 versus ≥ 3 was 95% v 71%, respectively, with a hazard ratio of 7.0. In multivariable analysis, MAI was superior to Adjuvant! and NBCG. The 10-year survival of Adjuvant! ≥ 95% versus less than 95% was 91% v 74%, respectively, but stratification by MAI identified subgroups with different prognosis. Similar results occurred for NBCG and MAI. Adjuvant! and NBCG were not prognostic to each other.

Conclusion

MAI is superior to Adjuvant! and NBCG in prognostication of patients with LN-negative breast cancer younger than age 55 years.

A signature inferred from Drosophila mitotic genes predicts survival of breast cancer patients

Introduction

The classification of breast cancer patients into risk groups provides a powerful tool for the identification of patients who will benefit from aggressive systemic therapy. The analysis of microarray data has generated several gene expression signatures that improve diagnosis and allow risk assessment. There is also evidence that cell proliferation-related genes have a high predictive power within these signatures.

Methods

We thus constructed a gene expression signature (the DM signature) using the human orthologues of 108 Drosophila melanogaster genes required for either the maintenance of chromosome integrity (36 genes) or mitotic division (72 genes).

Results

The DM signature has minimal overlap with the extant signatures and is highly predictive of survival in 5 large breast cancer datasets. In addition, we show that the DM signature outperforms many widely used breast cancer signatures in predictive power, and performs comparably to other proliferation-based signatures. For most genes of the DM signature, an increased expression is negatively correlated with patient survival. The genes that provide the highest contribution to the predictive power of the DM signature are those involved in cytokinesis.

Conclusion

This finding highlights cytokinesis as an important marker in breast cancer prognosis and as a possible target for antimitotic therapies.

Triple negativity and young age as prognostic factors in lymph node-negative invasive ductal carcinoma of 1 cm or less

BACKGROUND

Whether a systemic adjuvant treatment is needed is an area of controversy in patients with node-negative early breast cancer with tumor size of ≤1 cm, including T1mic.

METHODS

We performed a retrospective analysis of clinical and pathology data of all consecutive patients with node-negative T1mic, T1a, and T1b invasive ductal carcinoma who received surgery between Jan 2000 and Dec 2006. The recurrence free survival (RFS) and risk factors for recurrence were identified.

RESULTS

Out of 3889 patients diagnosed with breast cancer, 375 patients were enrolled (T1mic:120, T1a:93, T1b:162). Median age at diagnosis was 49. After a median follow up of 60.8 months, 12 patients developed recurrences (T1mic:4 (3.3%), T1a:2 (2.2%), T1b:6 (3.7%)), with a five-year cumulative RFS rate of 97.2%. Distant recurrence was identified in three patients. Age younger than 35 years (HR 4.91; 95% CI 1.014-23.763, p = 0.048) and triple negative disease (HR 4.93; 95% CI 1.312-18.519, p = 0.018) were significantly associated with a higher rate of recurrence. HER2 overexpression, Ki-67, and p53 status did not affect RFS.

CONCLUSIONS

Prognosis of node-negative breast cancer with T1mic, T1a and T1b is excellent, but patients under 35 years of age or with triple negative disease have a relatively high risk of recurrence.

The safety of temozolomide in the treatment of malignancies

BACKGROUND

Temozolomide (TMZ) has demonstrated clinical antitumor activity. In the US and the EU, TMZ is licensed for the treatment of glioblastoma multiforme concurrently with radiation followed by a maintenance treatment, and for refractory anaplastic astrocytoma or glioblastoma multiforme. TMZ is also approved for metastatic melanoma in > 20 countries worldwide.

OBJECTIVES

To ascertain the safety profile of TMZ.

METHODS

Synthesis of evidence from published clinical trials and the investigator's brochure of the manufacture.

CONCLUSION

For a cytotoxic cancer-treatment agent, TMZ has an acceptable safety profile. Lymphopenia is common in patients treated with all doses and schedules of TMZ. All patients receiving TMZ should be observed for lymphopenia and potential opportunistic infections, particularly when it is combined with other immune suppressive therapies.

Validating the prognostic value of proliferation measured by Phosphohistone H3 (PPH3) in invasive lymph node-negative breast cancer patients less than 71 years of age

We validated and compared the prognostic value of the proliferation marker phosphohistone H3 (PPH3) with classical variables in 241 T(1-2)N(0)M(0) breast cancer patients less than 71 years old with long-term follow-up (median 117 months) and without adjuvant treatment. PPH3 was measured by automated digital image analysis. Thirty-seven patients (15%) developed distant metastases and 29 (12%) died. The previously established PPH3 prognostic threshold H3 <13 (n = 157; 65% of all cases) vs. >or=13 (n = 84; 35% of all cases) was the strongest prognostic threshold exceeding all other characteristics, with 10-year recurrence-free survival of distant metastases of 96 and 64%, respectively (P = < 0.0001, hazard ratio = 7.8, 95% confidence interval = 3.4-17.9). PPH3 is robust as it showed high inter-observer reproducibility and was prognostic over wide range of thresholds around 13 and is the strongest prognostic variable in invasive node-negative breast cancer patients less than 71 years old.