Solitary but Sinister: A Pulmonary Nodule Detected Through Lung Cancer Screening Unveils Small Cell Lung Cancer

Small cell lung cancer (SCLC) is an aggressive malignancy that typically presents as a centrally located mass with early metastatic spread and only rarely manifests as a solitary pulmonary nodule (SPN) without lymphadenopathy. We report a 63-year-old active smoker whose low-dose computed tomography (LDCT) screening identified a 1.6 cm solitary nodule in the right lower lobe. Positron emission tomography (PET) confirmed metabolic activity without evidence of metastasis, although the nodule grew to 2.2 cm over six months. Robotic-assisted bronchoscopy with endobronchial ultrasound-guided biopsy revealed a high-grade neuroendocrine carcinoma. Immunohistochemical staining confirmed SCLC (TTF-1 positive, synaptophysin positive, p40 negative, Napsin A negative, and Ki-67 >80%). The tumor was staged as IA (T1c N0 M0), and the patient was considered a candidate for curative surgical resection. However, she succumbed to severe cardiovascular comorbidities prior to intervention. This case illustrates the "solitary but sinister" presentation of SCLC as a SPN and underscores the importance of maintaining a high index of suspicion, prompt tissue diagnosis, and expedited management in high-risk patients to avoid missing a narrow window for potentially curative treatment.