Quantitative Analysis of Cytologic Features: Application to Mucoepidermoid Carcinoma

Introduction: Cytologic diagnosis relies on recognition of morphologic features, yet the diagnostic value of individual cytologic features or their combinations is rarely quantified. In this study, we apply a quantitative cytologic feature analysis (QCFA) approach that treats each cytologic feature as a diagnostic test with measurable performance characteristics. Using mucoepidermoid carcinoma (MEC) as a model, we systematically assess and quantify the diagnostic utility of individual and combined cytomorphologic features. Methods: In this retrospective study (2002–2021), 95 salivary gland fine needle aspirates in which MEC was considered in the differential diagnosis were reviewed. Two cytopathologists scored 16 predefined features, including extracellular mucin and three types of vacuolated cells: mucocytes (columnar or cuboidal glandular cells with single mucin-filled vacuoles and eccentric nuclei), epimucocytes (similar to mucocytes but with a dense squamoid cytoplasmic rim), and non-mucinous empty vacuolated cells (containing sharply circumscribed empty vacuoles). Cytologic findings were correlated with follow-up histology, and contingency table analysis was used to calculate sensitivity, specificity, and likelihood ratios. Results: Of 95 cases, 49 (51.6%) were confirmed as MEC on histology. Epimucocytes were the most sensitive feature (0.90), while intermediate cells were the most specific (0.94). Extracellular mucin, mucocytes, and epidermoid cells were also predictive of MEC, whereas non-mucinous empty vacuolated cells were negatively associated with MEC (LR⁻ = 2.3). The combination of any mucinous feature (epimucocytes, mucocytes, or extracellular mucin) with either intermediate or squamous cells yielded optimal diagnostic performance (specificity 91%, LR⁺ 8.9). Conclusions: QCFA provides objective, quantitative support for established cytologic diagnostic criteria. Using MEC as a model, we introduce a standardized definition for epimucocytes and provide the first quantitative assessment of their diagnostic value. This study demonstrates the feasibility and value of applying rigorous quantitative metrics to individual and combined cytologic features, offering a systematic approach to evaluating morphologic criteria.