Interobserver variation in CD30 immunohistochemistry interpretation; consequences for patient selection for targeted treatment

AimsCD30 immunohistochemistry (IHC) in malignant lymphoma is used for selection of patients in clinical trials using brentuximab vedotin, an antibody drug-conjugate targeting the CD30 molecule. For reliable implementation in daily practice and meaningful selection of patients for clinical trials, information on technical variation and interobserver reproducibility of CD30 immunohistochemistry (IHC) staining is required. Methods and resultsWe conducted a three-round reproducibility assessment of CD30 scoring for categorised frequency and intensity, including a technical validation, a live polling' pre- and post-instruction scoring round and a web-based round including individual scoring with additional IHC information to mimic daily diagnostic practice. Agreement in all three scoring rounds was poor to fair ( = 0.12-0.35 for CD30-positive tumour cell percentage and = 0.16-0.41 for staining intensity), even when allowing for one category of freedom in percentage of tumour cell positivity ( = 0.30-0.61). The first round with CD30 staining performed in five independent laboratories showed objective differences in staining intensity. In the second round, approximately half the pathologists changed their opinion on CD30 frequency after a discussion on potential pitfalls, highlighting hesitancy in decision-making. Using fictional cut-off points for percentage of tumour cell positivity, agreement was still suboptimal ( = 0.35-0.60). ConclusionsLack of agreement in cases with heterogeneous expression is shown to influence patient eligibility for treatment with brentuximab vedotin, both in clinical practice and within the context of clinical trials, and limits the potential predictive value of the relative frequency of CD30-positive neoplastic cells for clinical response

Large B-cell Lymphomas of Immune-Privileged Sites Relapse via Parallel Clonal Evolution from a Common Progenitor B Cell

Large B-cell lymphoma of immune-privileged sites (LBCL-IP) arise in immune sanctuaries including the testis and central nervous system (CNS). After initially reaching complete response, relapses occur in almost 50% of patients, typically at other immune-privileged sites. Resolution of the clonal relationships and evolutionary patterns of LBCL-IP is required to understand the unique clinical behavior. We collected a unique set of 33 primary-relapse LBCL-IP sample pairs and performed next-generation sequencing for copy number, mutation, translocation, and immunoglobulin clonality analysis. All LBCL-IP sample pairs were clonally related, and both tumors developed from a common progenitor cell (CPC) with MYD88 and TBL1XR1 mutations and/or BCL6 translocations in 30/33 cases, indicating that these are early genetic events. This was succeeded by intermediate genetic events including shared, as well as unique alterations in targets of aberrant somatic hypermutation (aSHM), CD79B mutations, and 9p21.3/CDKN2A loss. Genetic alterations in genes involved in immune escape (HLA, CD274/PDCD1LG2) were predominantly unique in primary and relapse samples and thus considered late genetic events. Together, this study indicates that primary and relapsed LBCL-IP follow an early parallel evolutionary pattern where the CPC contains genetic alterations that support prolonged survival/proliferation and retention in a memory B-cell state, followed by germinal center reentry, aSHM and immune escape. SIGNIFICANCE: Genomic analyses reveal that primary and relapse LBCL-IP originate from a common progenitor cell with a small set of genetic alterations, followed by extensive parallel diversification, elucidating the clonal evolution of LBCL-IP

Pathology review identifies frequent misdiagnoses in recurrent classic Hodgkin lymphoma in a nationwide cohort:implications for clinical and epidemiological studies

Patients treated for classic Hodgkin lymphoma (CHL) have a reported 13-fold increased risk of developing subsequent non-Hodgkin lymphoma (NHL). In light of the growing awareness of CHL mimickers, this study re-assesses this risk based on an in-depth pathology review of a nationwide cohort of patients diagnosed with CHL in the Netherlands (2006-2013) and explores the spectrum of CHL mimickers. Among 2,669 patients with biopsy-proven CHL, 54 were registered with secondary NHL. On review, CHL was confirmed in 25/54 patients. In six of these, the subsequent lymphoma was a primary mediastinal B-cell lymphoma/mediastinal gray zone lymphoma, biologically related to CHL and 19/25 were apparently unrelated B-cell NHL. In 29/54 patients, CHL was reclassified as NHL, including T-cell lymphomas with secondary Hodgkin-like B-blasts (n=15), Epstein Barr virus-positive diffuse large B-cell lymphoma (n=8), CD30+ T-cell lymphoma (n=3) and indolent B-cell proliferations (n=3). Higher age, disseminated disease at presentation, extensive B-cell marker expression and association with Epstein-Barr virus were identified as markers to alert for CHL mimickers. Based on these data, the risk of developing NHL after CHL treatment was re-calculated to 3.6-fold (standardized incidence ratio 3.61; confidence interval: 2.29-5.42). In addition, this study highlights the clinicopathological pitfalls leading to misinterpretation of CHL and consequences for the care of individual patients, interpretation of trials and epidemiological assessments.</p