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Higher concordance of PD‐L1 expression between biopsies and effusions in epithelioid than in nonepithelioid pleural mesothelioma
Author(s) -
Mansour Mohammed S. I.,
Seidal Tomas,
Mager Ulrich,
Dobra Katalin,
Brunnström Hans,
Dejmek Annika
Publication year - 2021
Publication title -
cancer cytopathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.29
H-Index - 57
eISSN - 1934-6638
pISSN - 1934-662X
DOI - 10.1002/cncy.22401
Subject(s) - medicine , concordance , pathology , mesothelioma , cytology , histology , pleural effusion , biopsy , pleural disease , immunohistochemistry , clone (java method) , effusion , respiratory disease , lung , biology , surgery , dna , genetics
Background Malignant mesothelioma (MM) is a therapy‐resistant tumor, often causing an effusion. Drugs targeting the programmed cell death 1 (PD‐1)/programmed cell death ligand 1 (PD‐L1) pathway have shown promising results, but assessment of PD‐L1 expression to select patients for therapy has mainly been performed on histologic tissue samples. In a previous study, we showed that MM effusions are suitable for PD‐L1 assessment with results comparable to those reported in histologic studies, but no studies have compared PD‐L1 expression in histologic and cytologic samples. Methods PD‐L1 expression was determined immunohistochemically (clone 28‐8) in 61 paired samples of effusions and biopsies from patients with pleural MM, obtained at the time of diagnosis. Only cases with >100 tumor cells were included. Membranous staining in tumor cells was considered positive at ≥1%, >5%, >10%, and >50% cutoff levels. Results Of 61 histologic samples, PD‐L1 expression was found in 28 and 7 samples at ≥1% and >50% cutoffs, respectively; the corresponding figures for cytology were 21 and 5, respectively. The overall percentage agreement between histology and cytology was 69% and 84%, with a kappa (κ) of 0.36 and 0.08 at ≥1% and >50% cutoffs, respectively. The concordance between cytology and histology tended to be higher for epithelioid MM versus nonepithelioid MM at a ≥1% cutoff. PD‐L1 positivity in biopsies, but not in effusions, correlated with the histologic subtype at a ≥1% cutoff. Conclusions A moderate concordance of PD‐L1 expression between biopsies and effusions from pleural MM, especially for the epithelioid subtype, indicates biological differences between the 2 types of specimens. Cytology and histology may be complementary.