Added value of pathology consultations in cutaneous lymphomas: a 2-year review from the Dutch national referral and expertise centre.

Background: The accurate diagnosis of cutaneous lymphomas (CLs) and lymphoproliferative disorders presents significant challenges due to their rarity, the diversity of clinicopathological entities, and the necessity of integrating clinical, immunophenotypic, and molecular analyses with histopathology. Misdiagnosis and diagnostic delays are common, potentially leading to inappropriate treatments. The contribution of an expertise centre specifically for the pathology of CL has not been previously investigated.

Objectives: To evaluate the value of pathology consultations at the Dutch national referral centre for CLs focusing on diagnostic agreement and identifying common diagnostic pitfalls.

Methods: We retrospectively reviewed all pathology consultations concerning CLs received at the Leiden University Medical Centre during 2020 and 2021. Cases were categorized into informative and ambiguous conclusions. Diagnostic agreement between submitting and expert pathologists was assessed and categorized as essential agreement, more specific conclusion, minor disagreement, or major disagreement.

Results: A total of 239 consultations from 230 patients, were analysed. The submitted conclusion was categorized as informative in 64% of the consultations and as ambiguous in 36%. Most (59%) consultations in our study exhibited essential agreement with the submitting pathologist. The expert centre reduced ambiguous conclusions from 36% to 13%, primarily by resolving differential diagnostic considerations between lymphoma and pseudolymphomatous infiltrates. However, major diagnostic disagreements, with a potentially significant impact on treatment or prognosis, were found in 12% of consultations mostly involving reclassification from benign dermatoses to lymphomas. Mycosis fungoides, primary cutaneous follicle centre lymphoma, CD30-positive lymphoproliferative disorders, and pseudolymphomas were delineated as specific areas of diagnostic difficulty.

Conclusions: The findings indicate that a national referral and expertise centre for CL pathology contributes to ensuring accurate diagnoses and appropriate patient management. Our data encourage low-threshold consultation in an expert centre for all patients with clinical and/or histological suspicion of CL.