Utility of the cytological criteria in the diagnosis of malignant pleural mesothelioma: Making the bridge between theory and practice

Our plain-English summary of Utility of the cytological criteria in the diagnosis of malignant pleural mesothelioma: Making the bridge between theory and practice, by M. Mlika, R. Yaiche, R. Ayadi, et al (La Tunisie Médicale, 2023).

The study

• Authors: M. Mlika, R. Yaiche, R. Ayadi, E. Braham, M. Abdennadher, F. Mezni
• Journal: La Tunisie Médicale
• Published: 2023;101(5):497-501
• Read it: PubMed · Free full text

Abstract

Introduction: The diagnosis of malignant pleural mesothelioma (MPM) depends on microscopic examination performed on pleural biopsies taken under thoracoscopy. However, it has recently been established that cytology presents a significant diagnostic contribution enabling an earlier diagnosis with a minimally invasive procedure.

Aim: To assess the diagnostic value of consensual cytological features of MPM in the differentiation between adenocarcinoma, mesothelioma and reactive mesothelial cells in pleural liquid.

Methods: All available retrospective records from the computerized pathology database system and pathology reports were searched for malignant pleural effusion cytology specimens, over a 5-year period from January 2015 to February 2020. The cytological criteria based on the international Guidelines for cytopathologic diagnosis of epithelioid and mixed type of MPM were assessed. Malignant mesothelial cells, MNML and RL were considered as the gold standard.

Results: 189 pleural biopsies with their corresponding cytology specimens were available for review. Among the reviewed cytologies, the diagnoses of 21/189 pleural cytologies were modified. The highest sensitivities were attributed to cytoplasmic blebbing, hypercellularity and cell ball clusters. The most specific feature was the absence of extracellular granular hyaluronic acid cores in reactive cytology and the absence of intercellular openings in NMML cell clusters. Extracellular granular hyaluronic acid cores had the highest positive predictive value and the highest negative predictive value was attributed to the cytoplasmic blebbing in both reactive cytology and NMML.

Conclusion: These results highlight the fact that no sign is pathognomonic of the diagnosis of MPM pointing out the necessity of immunocytochemical techniques in equivocal cases.

In plain English

This retrospective, descriptive study tested how well microscopic features seen in pleural fluid samples (cytology) identify malignant pleural mesothelioma, using biopsy diagnoses as the reference. The authors reviewed 189 cases with both a pleural biopsy and cytology, taken from 2186 pleural biopsies received between January 2015 and February 2020. Biopsies showed adenocarcinoma in 100 cases, lymphoma in 30, small cell carcinoma in 20, squamous cell carcinoma in 5, malignant pleural mesothelioma in 7 and inflammatory processes in 27. Without immunocytochemistry, they checked each slide for ten features listed in international guidelines. On review, 21 of 189 cytology diagnoses were changed, including 3 reclassified as mesothelioma. Cytoplasmic blebbing was present in all mesothelioma cases (100% sensitivity). Hypercellularity, clustering, perinuclear vacuolization and multinucleation each had 75% sensitivity. The authors concluded that no single feature was diagnostic of mesothelioma and that immunocytochemistry is needed in equivocal cases. They described both the small number of mesotheliomas and the absence of immunocytochemistry as major limitations. The study did not examine asbestos exposure, and some of its reported figures disagree with one another.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Retrospective, descriptive diagnostic-accuracy study of cytological criteria, without immunocytochemistry, with tissue biopsy as the gold standard
• Who was studied: 189 cases with both a pleural biopsy and pleural cytology, out of 2186 pleural biopsies received from January 2015 to February 2020. Biopsy diagnoses: 100 adenocarcinomas, 30 lymphomas, 20 small cell carcinomas, 5 squamous cell carcinomas, 7 malignant pleural mesotheliomas and 27 inflammatory processes. Peritoneal cytologies were not included.
• Exposure: No asbestos or other exposure was studied. What the study assessed was whether each of ten guideline-listed cytological features was present on Papanicolaou-stained pleural fluid slides.
• Main results:
  • On review, 21 of 189 cytology diagnoses were changed: 18 suspect cytologies were reclassified as reactive, and 3 cases first called metastatic tumor were reclassified as mesothelioma.
  • After review, the authors reported 100% concordance between cytology and biopsy diagnoses.
  • Sensitivity for mesothelioma: hypercellularity 75%, clustering 75%, perinuclear vacuolization 75%, multinucleation 75%, and protrusions through the cell membrane (blebbing) 100%.
  • Extracellular granular hyaluronic acid cores had a sensitivity of 50% and a specificity of 100%.
  • Atypia had a sensitivity of 25% for mesothelioma.
• The authors' conclusion: The authors concluded that no single cytological criterion is diagnostic of mesothelioma, that the diagnosis may be suspected when many signs are present, and that equivocal cases need immunocytochemistry.
• Limitations the authors state:
  • Few malignant mesotheliomas were included, which the authors attributed to the rarity of the tumor.
  • The results may be hard to interpret because of the many diagnostic categories and cytological signs assessed.
  • Cytological criteria were analysed without immunocytochemistry, which the authors also called a major limitation.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Thoracoscopy, Cytology, Adenocarcinoma, Mesothelioma, Reactive Mesothelial Hyperplasia, Pathology, Pathology Report.

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