Cytologic atypia of benign inflammatory versus neoplastic cutaneous squamous lesions

Abstract Background Cytologic atypia encompasses several features of abnormal cellular morphology. We sought to quantify these features in benign and premalignant/malignant squamous cell lesions to better characterize criteria for malignancy. Methods We conducted a rater‐blinded observational study in which histopathology slides were evaluated under light microscopy, and the presence and relative quantity of 24 distinct cytological features were recorded, along with respective diagnoses. Each slide was evaluated, and the ratings were recorded and analyzed. Results The most helpful findings, whose presence in high numbers indicates an increased likelihood that the tissue sample is premalignant/malignant, were: (1) pleomorphic parakeratosis; (2) pleomorphic nuclei in the epithelium; (3) irregular nuclei; (4) thick refractile nuclear envelope; (5) presence of nuclear hyperchromasia (dark gray); (6) peripheral nucleoli; and (7) nucleolar stems. Higher values of round or oval nuclear shape and vesicular nuclei increase the likelihood that the tissue sample is benign. Conclusions Certain nuclear features have a higher association with premalignancy/malignancy and may guide histologic evaluation of a given lesion. These findings can be used in combination with architectural features and clinical history to add to a complete diagnostic picture.