Back to Basaloid: Revisiting the Diagnostic Dilemma of Basaloid Squamous Carcinoma Versus Small Cell Carcinoma on Lung Fine Needle Aspiration Biopsy Cytology

ABSTRACT Background Basaloid Squamous cell carcinoma (BSCC) is a rare subtype of squamous cell carcinoma whose cytomorphologic features on lung fine needle aspiration (FNAB) can mimic small cell lung carcinoma (SCLC), creating a diagnostic dilemma. As the distinction is critical for patient management and prognosis, this study aimed to determine if published cytological criteria can reliably differentiate these entities. Methods A 10‐year retrospective search of cytology archives yielded six cases of BSCC. These were compared to 15 confirmed SCLC cases. Key cytomorphologic parameters, including dispersal patterns, tissue fragment characteristics, architecture, and background elements, were systematically evaluated. Results BSCC cases consistently showed a predominantly cohesive tissue fragment pattern ( n = 6, 100%) with sharp, straight edges and peripheral palisading ( n = 6, 100%). Pseudorosettes ( n = 5, 83.3%) and keratinous debris ( n = 2, 33.3%) were also noted in BSCC. In contrast, SCLC cases typically showed discohesive cells and tissue fragments with irregular borders that lacked peripheral palisading. Conclusions Although no single feature is pathognomonic, a combination of architectural findings is useful in distinguishing BSCC from SCLC. The presence of cohesive tissue fragments with sharp edges and peripheral palisading strongly favors a diagnosis of BSCC.