Cytological Diagnostic Procedures in Malignant Mesothelioma

Malignant mesotheliomas (MM) are rare tumors with high mortality rates, whose incidence varies regionally and nationally, and the diagnosis is difficult. Histology-based diagnosis is considered the gold standard despite its low sensitivity of 57-84%. However, recent advances in cytological analysis offer promise for diagnostic advancements. In this study, we reappraised the current cytological guidelines for the MM diagnosis and concluded on their practicability and reliability. The study included 5731 consecutive specimens of pleural effusions from 4552 patients (3026 males of the average age of 67.5 years and 1526 females of the average age of 65.4 years) between December 2017 and January 2000. Out of these patients, 444 (9.8%) were diagnosed with MM. The effusions were examined by immunocytochemistry using routine Giemsa staining. Additionally, hyaluronic acid (HA) was assessed. Cytological findings confirmed 223 out of the 444 MM. The additional 88 cases with negative cytology were corroborated by supplemental assessments of HA above 30 mg/L. Cytological evaluation accomplished the sensitivity of 0.50, specificity of 0.99, and a positive predictive value (PPV) of 0.97 for MM diagnosis. The use of HA determination raised the sensitivity to 0.70 without affecting the specificity or PPV. We conclude that cytological evaluation of effusions aided by the assessment of HA demonstrates the diagnostic sensitivity and specificity for MM no less than the hitherto standard histological evaluation. The cytology-based MM diagnosis may thus be routinely considered when MM is suspected and may offer confirmatory advantages in difficult or doubtful diagnostic cases.