Diagnosis of thoracic SMARCA4 -deficient undifferentiated tumor in cytology

摘要

IntroductionAlthough alterations in SMARCA4-deficient occur in non-small cell lung carcinoma (SD-NSCLC), thoracic SMARCA4-deficient undifferentiated tumor (TSDUT) is recognized as a distinct entity in the 2021 World Health Organization Classification of Thoracic Tumors because of unique morphologic, immunophenotypic and molecular features, and worse survival compared with SD-NSCLC. Cytologic diagnosis of TSDUT is clinically important because of its aggressive behavior and because it is often diagnosed by fine-needle aspiration because TSDUTs are usually unresectable at presentation. Here, we identify cytologic features that can be used for recognition of TSDUT and distinction from SD-NSCLC. Materials and MethodsCytomorphologic features were investigated in cytology specimens from patients with TSDUT (n = 11) and compared with a control group of patients with SD-NSCLC (n = 20). ResultsThe presence of classic rhabdoid morphology, at least focally, was entirely specific for TSDUT (n = 6, 55) compared with SD-NSCLC (n = 0) in this study. TSDUT more frequently showed tumor necrosis (n = 11, 100 vs. n = 8, 40; p = .001), dominant single-cell pattern on aspirate smears or touch preparation slides (n = 8 of 9, 80 vs. n = 3, 15; p = .010), nuclear molding (n = 5, 45 vs. n = 1, 5; p = .013), and indistinct cell borders (n = 11, 100 vs. n = 5, 25; P < .001) compared with SD-NSCLC, respectively. ConclusionsCytomorphologic features occurring more frequently in TSDUT include tumor necrosis, dominant single-cell pattern, nuclear molding indistinct cell borders, and focal rhabdoid cells. Presence of these features in a cytology specimen of an undifferentiated tumor, particularly in a patient with a thoracic mass, should raise suspicion for TSDUT and prompt appropriate ancillary workup.