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Unexpected Dual Malignancy Case Report: Synchronous Bronchopulmonary Adenosquamous Carcinoma and Papillary Thyroid Carcinoma Revealed by 18F-FDG PET/CT

Year: 2026

Type: article

Abstract: Introduction Synchronous tumors are defined as two or more distinct primary neoplasms of different histological origin occurring simultaneously in the same individual. In most cases, the second malignancy is discovered incidentally during the diagnostic evaluation or treatment of the first tumor. The association between differentiated thyroid carcinoma and lung cancer has been reported, but the coexistence of bronchopulmonary adenosquamous carcinoma and papillary thyroid carcinoma remains extremely rare. Case Presentation We report the case of a 47-year-old North African woman with a history of diabetes mellitus treated with insulin and metformin, and uveitis treated with corticosteroids, who presented with persistent cough. Bronchoscopic biopsy revealed bronchopulmonary adenosquamous carcinoma in situ. To evaluate the extent of disease, a whole-body 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) scan was performed. Imaging demonstrated a hypermetabolic pulmonary nodule in the anterior basal segment of the left lower lobe associated with an FDG-avid right subhilar lesion. Additionally, PET/CT revealed an incidental hypermetabolic thyroid nodule in the left thyroid lobe. The patient subsequently underwent left lung lobectomy, and histopathological examination confirmed bronchopulmonary adenosquamous carcinoma. Because of the PET/CT thyroid finding, cervical ultrasound and fine-needle aspiration cytology were performed, revealing an oncocytic follicular neoplasm. Total thyroidectomy was therefore carried out. Histological examination revealed two foci of papillary thyroid carcinoma measuring 1.0 cm and 1.3 cm with capsular involvement. The patient subsequently received high-dose radioiodine therapy (100 mCi of iodine-131). Post-therapy whole-body scintigraphy demonstrated intense cervical uptake consistent with thyroid remnant tissue. At 9-month follow-up, the patient remained in remission for thyroid carcinoma and under surveillance for pulmonary disease. Conclusion The coexistence of bronchopulmonary adenosquamous carcinoma and papillary thyroid carcinoma is exceptionally rare. Whole-body 18F-FDG PET/CT plays a crucial role in the detection of synchronous primary malignancies by identifying unexpected hypermetabolic lesions, thereby improving diagnostic accuracy and enabling timely and appropriate therapeutic management.

Source: Case Reports in Oncology

DOI: 10.1159/cro/abzag058