Color Standardization and Stain Intensity Calibration for Whole Slide Image-Based Immunohistochemistry Assessment

Automated quantification of human epidermal growth factor receptor 2 (HER2) immunohistochemistry (IHC) using whole slide imaging (WSI) is expected to eliminate subjectivity in visual assessment. However, the color intensity in WSI varies depending on the staining process and scanner device. Such variations affect the image analysis results. This paper presents methods to diminish the influence of color variation produced in the staining process using a calibrator slide consisting of peptide-coated microbeads. The calibrator slide is stained along with tissue sample slides, and the 3,3'-diaminobenzidine (DAB) color intensities of the microbeads are used for calibrating the color variation of the sample slides. An off-the-shelf image analysis tool is employed for the automated assessment, in which cells are classified by the thresholds for the membrane staining. We have adopted two methods for calibrating the color variation based on the DAB color intensities obtained from the calibrator slide: (1) thresholds for classifying the DAB membranous intensity are adjusted, and (2) the color intensity of WSI is corrected. In the experiment, the calibrator slides and tissue of breast cancer slides were stained together on different days and used to test our protocol. With the proposed protocol, the discordance in the HER2 evaluation was reduced to one slide out of 120 slides.

Quality Management System in Clinical Digital Pathology Operations at a Tertiary Cancer Center

Digital pathology workflows can improve pathology operations by allowing reliable and fast retrieval of digital images, digitally reviewing pathology slides, enabling remote work and telepathology, use of computer-aided tools, and sharing of digital images for research and educational purposes. The need for quality systems is a prerequisite for successful clinical-grade digital pathology adoption and patient safety. In this article, we describe the development of a structured digital pathology laboratory quality management system (QMS) for clinical digital pathology operations at Memorial Sloan Kettering Cancer Center (MSK). This digital pathology-specific QMS development stemmed from the gaps that were identified when MSK integrated digital pathology into its clinical practice. The digital scan team in conjunction with the Department of Pathology and Laboratory Medicine quality team developed a QMS tailored to the scanning operation to support departmental and institutional needs. As a first step, systemic mapping of the digital pathology operations identified the prescan, scan, and postscan processes; instrumentation; and staffing involved in the digital pathology operation. Next, gaps identified in quality control and quality assurance measures led to the development of standard operating procedures and training material for the different roles and workflows in the process. All digital pathology-related documents were subject to regulatory review and approval by departmental leadership. The quality essentials were developed into an extensive Digital Pathology Quality Essentials framework to specifically address the needs of the growing clinical use of digital pathology technologies. Using the unique digital experience gained at MSK, we present our recommendations for QMS for large-scale digital pathology operations in clinical settings.

The African Research Group for Oncology: A decade fostering colorectal cancer research in Nigeria

The African Research Group for Oncology (ARGO) was formed in 2013 to undertake methodologically rigorous cancer research in Nigeria, and to strengthen cancer research capacity in the country through training and mentorship of physicians, scientists, and other healthcare workers. Here, we describe how ARGO's work in colorectal cancer (CRC) has evolved over the past decade. This includes the consortium's scientific contributions to the understanding of CRC in Nigeria and globally and its research capacity-building program.

Standardizing HER2 immunohistochemistry assessment: calibration of color and intensity variation in whole slide imaging caused by staining and scanning

In the evaluation of human epidermal growth factor receptor 2 (HER2) immunohistochemistry (IHC) - one of the standard biomarkers for breast cancer- visual assessment is laborious and subjective. Image analysis using whole slide image (WSI) could produce more consistent results; however, color variability in WSIs due to the choice of stain and scanning processes may impact image analysis. We therefore developed a calibration protocol to diminish the staining and scanning variations of WSI using two calibrator slides. The IHC calibrator slide (IHC-CS) contains peptide-coated microbeads with different concentrations. The color distribution obtained from the WSI of stained IHC-CS reflects the staining process and scanner characteristics. A color chart slide (CCS) is also useful for calibrating the color variation due to the scanner. The results of the automated HER2 assessment were compared to confirm the effectiveness of two calibration slides. The IHC-CS and HER2 breast cancer cases were stained on different days. All stained slides and CCS were digitized by two different WSI scanners. Results revealed 100% concordance between automated evaluation and the pathologist's assessment with both the scanner and staining calibration. The proposed method may enable consistent evaluation of HER2.

Digital pathology operations at a tertiary cancer center: Infrastructure requirements and operational cost

Whole slide imaging is revolutionizing the field of pathology and is currently being used for clinical, educational, and research initiatives by an increasing number of institutions. Pathology departments have distinct needs for digital pathology systems, yet the cost of digital workflows is cited as a major barrier for widespread adoption by many organizations. Memorial Sloan Kettering Cancer Center (MSK) is an early adopter of whole slide imaging with incremental investments in resources that started more than 15 years ago. This experience and the large-scale scan operations led to the identification of required framework components of digital pathology operations. The cost of these components for the 2021 digital pathology operations at MSK were studied and calculated to enable an understanding of the operation and benchmark the accompanying costs. This paper describes the unique infrastructure cost and the costs associated with the digital pathology clinical operation use cases in a large, tertiary cancer center. These calculations can serve as a blueprint for other institutions to provide the necessary concepts and offer insights towards the financial requirements for digital pathology adoption by other institutions.

Abstract P2-23-17: Programmed death ligand-1 expression in triple-negative breast cancer from Nigeria

Introduction: The incidence of triple negative breast cancer (TNBC) in West Africa appears to mirror the higher incidence of the disease among African American women in the United States. However, there remains a paucity of molecular data on TNBC from sub-Saharan Africa, despite the emergence of effective immunotherapies. Methods: Consecutive patients diagnosed with invasive breast cancer between March 2018-Jan 2020 were identified from a prospective clinical database and paired biobank at Obafemi Awolowo University Teaching Hospital (OAUTH). All specimens were processed and fixed in formalin within 60 minutes of excision by a trained pathologist. Tissue sections (4μm thick) representative of tumor were selected for routine evaluation of estrogen, progesterone and human epidermal growth factor receptor-2 expression by immunohistochemistry. This was performed at OAUTH with adequate controls according to the ASCO/CAP guidelines and verified at an outside institution for quality assurance. Additional sections from the FFPE blocks of TNBC specimens were further stained using the Dako PharmDx 22C3 PD-L1 commercial assay according to manufacturer protocols at Dalhousie University. External on-slide controls included tonsil, PD-L1 negative TNBC, and PD-L1 positive TNBC. PD-L1 expression was scored using the combined positive score (CPS), which is the number of 22C3 staining tumour cells, lymphocytes, and macrophages divided by the number of viable tumour cells, multiplied by 100. The threshold for a positive result was a CPS of ≥10 as per manufacturer instructions and institutional protocol. Research ethics board approval as well as data and material transfer agreements between institutions was obtained for this study. Results: From 85 cases, 32 were TNBC (37.6%). The mean age and BMI were 49.6±SD 7.7 and 26.2±5.7, respectively. The majority of patients presented with locally advanced disease (64.2% Stage III, 14.2% Stage IV). Seventy-nine percent (78.5%) of patients received an average of five cycles of neoadjuvant chemotherapy (SD 2.3). From 32 TNBC specimens, 27 had available FFPE tissue blocks, and of those, 24 had interpretable PD-L1 IHC for inclusion in the analysis. A total of 37.5% (9/24) of cases demonstrated a CPS ≥10. Conclusions: Over a third of breast cancer specimens in this Nigerian cohort were triple negative, 37.5% of which had PD-L1 CPS scores of ≥10. These results suggest a large proportion of patients in Nigeria may benefit from access to immunotherapy. This is the first reported incidence of PD-L1 expression in breast cancer from sub-Saharan Africa.

Citation Format: Olalekan Olasehinde, Funmilola Wuraola, Aleksandra Kajetanowicz, Gilllian Bethune, Marcia Edelweiss, Peter Ntiamoah, Oluwole Odujoko, Avinash Sharma, Victoria Mango, Peter Kingham, Olusegun Alatise, Gregory Knapp. Programmed death ligand-1 expression in triple-negative breast cancer from Nigeria [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-23-17.

Pathological Evaluation of Rectal Cancer Specimens Using Micro-Computed Tomography

Whole-block imaging (WBI) using micro-computed tomography (micro-CT) allows the nondestructive reconstruction of a three-dimensional view of tissues, implying that WBI may be used for accurate pathological evaluation of patients with rectal cancer. HOWEVER, the clinical impact of this approach is unclear. We aimed to clarify the efficacy of WBI in the whole-mount specimens of locally advanced rectal cancer. A total of 237 whole-mount formalin-fixed paraffin-embedded blocks from 13 patients with rectal cancer who underwent surgical treatment were enrolled and scanned with micro-CT to generate three-dimensional images. WBI was evaluated following the conventional pathological review of the corresponding whole-slide imaging (WSI). WBI identified all tumor sites detected using WSI. Furthermore, WBI revealed one additional tumor site, which was not detected using WSI. Tumor resection margin was significantly closer to the soft-tissue edge when measured using WBI (7.7 mm vs. 6.6 mm, p < 0.01). Seventy-six percent of tumor deposits on WSI were changed according to the evidence of tumor interaction with the surrounding tissues confirmed using WBI. Furthermore, WBI revealed 25 additional lymph nodes, six of which were metastatic. The combination of conventional hematoxylin and eosin-stained imaging and WBI may contribute to an accurate pathological assessment.

Micro-computed tomography: A novel diagnostic technique for the evaluation of gastrointestinal specimens

Micro-computed tomography (micro-CT) is a non-destructive modality that can be used to obtain high-resolution three-dimensional (3 D) images of the whole sample tissue; the usefulness of micro-CT has been reported for evaluation of breast cancer and lung cancer. However, this novel diagnostic technique has never been used for evaluating endoscopically resected gastrointestinal specimens. In the present study, we scanned 13 formalin-fixed paraffin-embedded (FFPE) tissue blocks of a normal human colon and gastric tissue samples using micro-CT. The evaluation comprised a comparison of the acquired whole block images with the images of the corresponding cross-sectional slice of the hematoxylin and eosin-stained slide. Micro-CT was able to produce images of the whole sample and clearly depict tissues such as glandular structures, muscularis mucosae, and blood vessels in the FFPE tissue blocks of normal gastrointestinal samples. Furthermore, the 3 D reconstructed could be used to create a cross-sectional image and reflected the surface structure of samples obtained from any site. Micro-CT has the potential to become a highly promising pathological diagnostic assistance tool for endoscopically resected gastrointestinal specimens in combination with conventional microscopic examination.

Deep Multi-Magnification Networks for multi-class breast cancer image segmentation

Pathologic analysis of surgical excision specimens for breast carcinoma is important to evaluate the completeness of surgical excision and has implications for future treatment. This analysis is performed manually by pathologists reviewing histologic slides prepared from formalin-fixed tissue. In this paper, we present Deep Multi-Magnification Network trained by partial annotation for automated multi-class tissue segmentation by a set of patches from multiple magnifications in digitized whole slide images. Our proposed architecture with multi-encoder, multi-decoder, and multi-concatenation outperforms other single and multi-magnification-based architectures by achieving the highest mean intersection-over-union, and can be used to facilitate pathologists' assessments of breast cancer.

Digital Pathology Operations at an NYC Tertiary Cancer Center During the First 4 Months of COVID-19 Pandemic Response

Implementation of an infrastructure to support digital pathology began in 2006 at Memorial Sloan Kettering Cancer Center. The public health emergency and COVID-19 pandemic regulations in New York City required a novel workflow to sustain existing operations. While regulatory enforcement discretions offered faculty workspace flexibility, a substantial portion of laboratory and digital pathology workflows require on-site presence of staff. Maintaining social distancing and offering staggered work schedules. Due to a decrease in patients seeking health care at the onset of the pandemic, a temporary decrease in patient specimens was observed. Hospital and travel regulations impacted onsite vendor technical support. Digital glass slide scanning activities onsite proceeded without interruption throughout the pandemic, with challenges including staff who required quarantine due to virus exposure, unrelated illness, family support, or lack of public transportation. During the public health emergency, we validated digital pathology systems for a remote pathology operation. Since March 2020, the departmental digital pathology staff were able to maintain scanning volumes of over 100 000 slides per month. The digital scanning team reprioritized archival slide scanning and participated in a remote sign-out validation and successful submission of New York State approval for a laboratory developed test. Digital pathology offers a health care delivery model where pathologists can perform their sign out duties at remote location and prevent disruptions to critical pathology services for patients seeking care at our institution during emergencies. Development of standard operating procedures to support digital workflows will maintain turnaround times and enable clinical operations during emergency or otherwise unanticipated events.

Discordant DNA mismatch repair protein status between synchronous or metachronous gastrointestinal carcinomas: frequency, patterns, and molecular etiologies

The widespread use of tumor DNA mismatch repair (MMR) protein immunohistochemistry in gastrointestinal tract (GIT) carcinomas has unveiled cases where the MMR protein status differs between synchronous/metachronous tumors from the same patients. This study aims at examining the frequency, patterns and molecular etiologies of such inter-tumoral MMR discordances. We analyzed a cohort of 2159 colorectal cancer (CRC) patients collected over a 5-year period and found that 1.3% of the patients (27/2159) had ≥ 2 primary CRCs, and 25.9% of the patients with ≥ 2 primary CRCs (7/27) exhibited inter-tumoral MMR discordance. We then combined the seven MMR-discordant CRC patients with three additional MMR-discordant GIT carcinoma patients and evaluated their discordant patterns and associated molecular abnormalities. The 10 patients consisted of 3 patients with Lynch syndrome (LS), 1 with polymerase proofreading-associated polyposis (PAPP), 1 with familial adenomatous polyposis (FAP), and 5 deemed to have no cancer disposing hereditary syndromes. Their MMR discordances were associated with the following etiologies: (1) PMS2-LS manifesting PMS2-deficient cancer at an old age when a co-incidental sporadic MMR-proficient cancer also occurred; (2) microsatellite instability-driven secondary somatic MSH6-inactivation occurring in only one-and not all-PMS2-LS associated MMR-deficient carcinomas; (3) "compound LS" with germline mutations in two MMR genes manifesting different tumors with deficiencies in different MMR proteins; (4) PAPP or FAP syndrome-associated MMR-proficient cancer co-occurring metachronously with a somatic MMR-deficient cancer; and (5) non-syndromic patients with sporadic MMR-proficient cancers co-occurring synchronously/metachronously with sporadic MMR-deficient cancers. Our study thus suggests that inter-tumoral MMR discordance is not uncommon among patients with multiple primary GIT carcinomas (25.9% in patients with ≥ 2 CRCs), and may be associated with widely varied molecular etiologies. Awareness of these patterns is essential in ensuring the most effective strategies in both LS detection and treatment decision-making. When selecting patients for immunotherapy, MMR testing should be performed on the tumor or tumors that are being treated.

Chromosome 3p loss of heterozygosity and reduced expression of H3K36me3 correlate with longer relapse-free survival in sacral conventional chordoma

Conventional chordoma is a rare slow-growing malignant tumor of notochordal origin primarily arising at the base of the skull and sacrococcygeal bones. Chordoma may arise from its benign counterpart, benign notochordal cell tumors, and can also undergo dedifferentiation progressing into dedifferentiated chordoma. No study has directly compared the genomic alterations among these tumors comprising a morphologic continuum. Our prior study identified frequent chromosome 3p loss of heterozygosity and minimal deleted regions on chromosome 3 encompassing SETD2, encoding a histone methyltransferase involved in histone H3 lysine 36 trimethylation (H3K36me3). In the present study, we expanded our study to include 65 sacral conventional chordoma cases, 3 benign notochordal cell tumor cases, and 2 dedifferentiated chordoma cases using single nucleotide polymorphism (SNP) array, targeted next-generation sequencing analysis, and immunohistochemistry. We performed immunohistochemical analysis of histone, H3K36me3, and investigated whether there is any association between the clinical behavior and recurrent chromosome or aneuploidy or H3K36me3 protein expression. We found that there is increased genomic instability from benign notochordal cell tumor to conventional chordoma to dedifferentiated chordoma. The highly recurrent genomic aberration, chromosome 3p loss of heterozygosity (occurred in 70% of conventional chordomas), is correlated with longer relapse-free survival, but not with overall survival or metastasis-free survival in sacral chordoma. Chordomas demonstrate variable patterns and levels of H3K36me3 expression, and reduced expression of H3K36me3 showed marginally significant correlation with longer relapse-free survival. Copy number alterations in the genes encoding the H3K36me3 methylation transferase complex and demethylase may account for the altered H3K36me3 expression levels.

Developing a breast cancer tissue biobank in low and middle income countries (LMICs): A research program-based approach for improving molecular profiling

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Background: Breast cancer incidence and mortality is increasing in LMICs especially in sub-Saharan Africa, attributed to changes in lifestyle and possible biological differences. To study putative relationships among lifestyle factors, tumor biology, and the microenvironment, we aimed to develop a breast cancer tissue biobank linked with clinicopathologic and patient reported data in this resource constrained setting. Methods: We prospectively enrolled patients undergoing mastectomy at Obafemi Awolowo University Teaching hospital in Ile-Ife, Nigeria. Pre-operatively, a locally validated survey tool assessed lifestyle factors (diet and exercise); BMI and body composition (by bioimpedence) were measured. Fresh breast tissue was frozen or preserved in 10% neutral buffered formalin, or RNA later for future metabolomic work. Immunohistochemistry (IHC) for ER/PR and HER2 status was performed and read in Nigeria by a locally-trained pathologist, and Memorial Sloan Kettering. The primary outcome was feasibility assessed by successful collection of tissue, clinicopathologic data, and survey completion. Secondary outcomes were completion rate of tumor receptor IHC compared to historic rates and concordance of local vs MSK IHC. Results: From April 2018 to June 2019, 50 patients were enrolled (49 treatment and 1 risk reduction mastectomy). Clinicopathologic, body composition, and survey data, along with breast tissue were collected from all 50 patients. Patient characteristics in table below. Receptor IHC was complete in all patients (100%) compared to a historic rate of 29% (83/286) between 2010-17. Concordance of IHC between sites was 86%, 81% and 84% for subtypes (ER/PR/HER2). Conclusions: Establishing a tissue biobank with clinicopathologic and lifestyle data using locally-adapted protocols is feasible in Nigeria. Patient enrolment is ongoing and updated data will be presented. This initiative also increased local capacity for breast tumor phenotyping, which has critical implications for improving patient care. [Table: see text]

Pathology Services in Nigeria: Cross-Sectional Survey Results From Three Cancer Consortia

PURPOSE

Cancer incidence is increasing in sub-Saharan Africa, yet there is little information on the capacity of pathology laboratories in this region. We aimed to assess the current state of pathology services in Nigeria to guide strategies to ensure best practices and improve the quality of surgical specimen handling.

METHODS

We developed structured pathology survey to assess tissue handling, sample processing, and immunohistochemistry (IHC) capabilities. The survey was distributed electronically to 22 medical centers in Nigeria that are part of established cancer consortia. Data were collected between September and October 2017.

RESULTS

Sixteen of 22 centers completed the survey in full. All 16 institutions had at least one board-certified pathologist and at least one full-time laboratory scientist/technologist. The majority of responding institutions (75%) reported processing fewer than 3,000 samples per year. For sample processing, 38% of institutions reported manual tissue processing and 75% processed biopsies and surgical specimens together. The average tissue fixation time ranged from 5 to more than 72 hours before processing and paraffin embedding. Half of the institutions reported having no quality assurance processes to evaluate hematoxylin and eosin–stained slides, and 25% reported having no written operating procedures. Half of the participating institutions have a facility for routine IHC staining, and among these there was considerable variability in processes and validation procedures. External proficiency testing was not common among surveyed sites (38%).

CONCLUSION

Data from 16 Nigerian medical institutions indicate deficiencies in standardization, quality control, and IHC validation that could affect the reliability of pathology results. These findings highlight addressable gaps in pathology services that can ensure accurate diagnosis and follow-up for the growing number of patients with cancer in this region.

A rectal cancer organoid platform to study individual responses to chemoradiation

Rectal cancer (RC) is a challenging disease to treat that requires chemotherapy, radiation and surgery to optimize outcomes for individual patients. No accurate model of RC exists to answer fundamental research questions relevant to patients. We established a biorepository of 65 patient-derived RC organoid cultures (tumoroids) from patients with primary, metastatic or recurrent disease. RC tumoroids retained molecular features of the tumors from which they were derived, and their ex vivo responses to clinically relevant chemotherapy and radiation treatment correlated with the clinical responses noted in individual patients' tumors. Upon engraftment into murine rectal mucosa, human RC tumoroids gave rise to invasive RC followed by metastasis to lung and liver. Importantly, engrafted tumors displayed the heterogenous sensitivity to chemotherapy observed clinically. Thus, the biology and drug sensitivity of RC clinical isolates can be efficiently interrogated using an organoid-based, ex vivo platform coupled with in vivo endoluminal propagation in animals.

Application of large format tissue processing in the histology laboratory

In clinical, research and veterinary laboratories of North America, large format histology has more recently been improved with newer equipment and better methodology. Large tissue specimens are frequently sliced in the grossing room and processed in multiple smaller, standard size tissue cassettes. Justifiably, submitting more blocks inherently lends itself to a greater confidence in the accuracy of the diagnosis, yet guidelines for tissue sampling often suggest taking fewer samples. For example, large tumor specimen protocols recommend taking one standard-sized tissue block for each cm diameter of tumor. However, cancers are the culmination of many complex changes in cell metabolism and often appear dissimilar at different tissue locations. As these changes have an uncertain behavior, many other tissue samples are often taken from areas that appear to have either a variable texture or color. Consequently, at microscopy, the complete tissue sample may need to be reassembled like a jigsaw puzzle as the stained sections are frequently presented over many slides. This problem has easily been overcome by using large format cassettes since the entire cross-section of the tissue sample can often be viewed on a single slide. Because these cassettes can effectively hold up to 10 times the volume of conventional standard size cassettes, they are a more efficient way of assessing large areas of tissue samples. This system is easily adapted for all tissue types and has become the established method for assessing large tissue samples in many laboratory settings.

Cellular localization of PD-L1 expression in mismatch-repair-deficient and proficient colorectal carcinomas

Blockade of the interaction between PD-1 and its ligands PD-L1 has shown clinical efficacy across several tumor types, especially in mismatch-repair-deficient colorectal carcinoma. The aim of this study was to examine the pattern and cellular localization of PD-L1 expression in the different molecular subtypes of mismatch-repair-deficient colorectal cancers vs. their mismatch-repair-proficient counterparts. PD-L1/SATB2 double-antibody-immunohistochemistry was utilized to distinguish tumor cell from immune cell staining. We observed in our series of 129 colorectal adenocarcinomas that PD-L1 expression occurred primarily in tumor-associated-immune cells and most prominently at the tumor-stroma-interface of the invasive front. The level of invasive front immune cell staining was significantly higher in mismatch-repair-deficient tumors compared to mismatch-repair-proficient tumors (p < 0.001), but no difference was observed among the different subtypes of mismatch-repair-deficient tumors: Lynch syndrome-associated vs. MLH1-methylated vs. unexplained. While selected mismatch-repair-proficient tumors exhibited unusually high tumor-infiltrating-lymphocytes and had high level immune cell PD-L1 expression, a positive correlation between PD-L1 expression and high lymphocyte count was detected only in mismatch-repair-deficient tumors (r = 0.39, p < 0.001) and not in mismatch-repair-proficient tumors. Notably, true tumor cell PD-L1 expression in colorectal carcinoma was rare, present in only 3 of 129 tumors (2.3%): 2 MLH1-methylated and 1 mismatch-repair-proficient with high tumor-infiltrating-lymphocytes; and the staining in the tumor cells in all 3 was diffuse (>=50% of the tumor). These findings may serve to inform further efforts aiming to evaluate PD-L1 immunohistochemistry vis-à-vis molecular sub-classification as predictive biomarkers in the treatment of colorectal carcinoma.

SMAD4 Loss in Colorectal Cancer Patients Correlates with Recurrence, Loss of Immune Infiltrate, and Chemoresistance

PURPOSE

SMAD4 has shown promise in identifying patients with colorectal cancer at high risk of recurrence or death.Experimental Design: A discovery cohort and independent validation cohort were classified by SMAD4 status. SMAD4 status and immune infiltrate measurements were tested for association with recurrence-free survival (RFS). Patient-derived xenografts from SMAD4-deficient and SMAD4-retained tumors were used to examine chemoresistance.

RESULTS

The discovery cohort consisted of 364 patients with stage I-IV colorectal cancer. Median age at diagnosis was 53 years. The cohort consisted of 61% left-sided tumors and 62% stage II/III patients. Median follow-up was 5.4 years (interquartile range, 2.3-8.2). SMAD4 loss, noted in 13% of tumors, was associated with higher tumor and nodal stage, adjuvant therapy use, fewer tumor-infiltrating lymphocytes (TIL), and lower peritumoral lymphocyte aggregate (PLA) scores (all P < 0.04). SMAD4 loss was associated with worse RFS (P = 0.02). When stratified by SMAD4 and immune infiltrate status, patients with SMAD4 loss and low TIL or PLA had worse RFS (P = 0.002 and P = 0.006, respectively). Among patients receiving 5-fluorouracil (5-FU)-based systemic chemotherapy, those with SMAD4 loss had a median RFS of 3.8 years compared with 13 years for patients with SMAD4 retained. In xenografted mice, the SMAD4-lost tumors displayed resistance to 5-FU. An independent cohort replicated our findings, in particular, the association of SMAD4 loss with decreased immune infiltrate, as well as worse disease-specific survival.

CONCLUSIONS

Our data show SMAD4 loss correlates with worse clinical outcome, resistance to chemotherapy, and decreased immune infiltrate, supporting its use as a prognostic marker in patients with colorectal cancer.

Histone H3K36M mutation and trimethylation patterns in chondroblastoma

AIMS

Histones are essential components of chromatin, and mutations in histones lead to alterations in methylation and acetylation, which play an important role in tumorigenesis. Most of the chondroblastomas harbour the H3K36M mutation. With the availability of a mutation-specific antibody, we sought to assess the sensitivity of this antibody and the alterations of histone methylation in a series of chondroblastoma cases.

METHODS AND RESULTS

Immunohistochemical staining with antibodies against H3K36M, trimethylated histones (H3K27me3 and H3K36me3) and an osteoblastic marker (SATB2) was performed on 27 chondroblastomas from 27 patients. The clinical and radiological characteristics of each patient were reviewed. All 27 tumours showed typical radiological and histological features of chondroblastoma, with a subset of cases showing secondary aneurysmal bone cyst changes (11/27), giant-cell-rich foci (4/27), and matrix-rich areas mimicking chondromyxoid fibroma (1/27). All except one case (26/27, 96%) showed positive H3K36M immunostaining (nuclear). In the majority of cases, there was a diffuse staining pattern. Immunohistochemical staining for H3K27me3 and H3K36me3 showed a heterogeneous staining pattern in all cases, regardless of mutation status. None of the cases showed loss of positivity or diffuse positivity. Focal or diffuse SATB2 expression was seen in 21 of 26 tumours (81%).

CONCLUSION

Our results demonstrate that the vast majority of chondroblastomas are positive for H3K36M by immunohistochemical analysis, confirming its diagnostic value. H3K27me3 expression and H3K36me3 expression are heterogeneous in these tumours.