Abstract Introduction Silicosis is a pneumoconiosis caused by chronic inhalation of crystalline silica, classically associated with occupational exposure. Non-occupational cases are rare and can pose significant diagnostic challenges, often mimicking malignancy. We present the case of a patient with no occupational exposures whose FDG-avid pulmonary and mediastinal nodal lesions raised strong concern for lung cancer but were ultimately diagnosed as non-occupational silicosis from chronic exposure to silica-containing cat litter. Description A 69-year-old woman with no significant past medical history presented for evaluation of an abnormal chest radiograph obtained after a persistent cough. She denied other constitutional symptoms, history of smoking, or occupational dust exposure. Physical examination was unremarkable. Chest CT demonstrated a 2.0 cm right apical spiculated nodule extending to the pleura. PET-CT revealed the lesion to be FDG-avid (SUVmax 5.1) with uptake in right suprahilar and paratracheal lymph nodes (SUVmax 2.8 and 3.8, respectively) and an incidental FDG-avid thyroid nodule (SUVmax 3.5). Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) of lymph node stations 4L, 7, 4R, and 11R demonstrated silicotic changes and scant atypical cells in station 4R without definitive malignancy. Thyroid fine-needle aspiration revealed one benign and one indeterminate (Bethesda III) nodule. Due to persistent concern for malignancy, robotic-assisted bronchoscopy was performed. Intraoperative CT demonstrated interval reduction in the right upper lobe nodule size, and biopsy was deferred. Repeat EBUS-TBNA of station 4R again showed benign cytology. Pathologic evaluation revealed numerous small birefringent crystalline particles consistent with silicate material. Upon detailed reevaluation of potential environmental exposures, the patient disclosed chronic handling of domestic silica-containing cat litter. The litter, used for 20 indoor cats, was exclusively poured indoors, providing a plausible source of chronic inhalational exposure. Discussion This case highlights the diagnostic complexity of distinguishing silica-related inflammation from malignancy, as FDG-avid pulmonary and mediastinal lesions often trigger extensive oncologic evaluation. Absence of granulomas suggested a non-granulomatous inflammatory variant of silicosis. Particularly novel was the finding of an FDG-avid spiculated nodule that nearly resolved within two months—a pattern not previously reported in non-occupational silicosis. This rapid radiographic improvement supported a benign inflammatory process rather than malignancy and underscores the dynamic nature that silica-induced inflammation can exhibit. Non-occupational silicosis from cat litter exposure is a rare but important mimicker of lung cancer, emphasizing the need for thorough exposure history, histopathologic confirmation, and multidisciplinary evaluation to prevent unnecessary invasive procedures and patient anxiety. This abstract is funded by: None
Camilion et al. (Fri,) studied this question.