A hidden lung cancer in a patient with granulomatosis with polyangiitis

Granulomatosis with polyangiitis is a systemic necrotizing vasculitis that affects the small- and medium-sized blood vessels. The diagnosis can be challenging since the clinical and imaging findings have similarities with infection, and malignancy. Serologic and histopathological investigations often help confirm the diagnosis. However, this can be falsely reassuring. We present a unique case of the coexistence of vasculitis and squamous cell carcinoma in the same cavitating lung mass. The case highlights the importance of recognizing changes in disease behaviour early to allow for timely management.