A rare pathology that mimics lung cancer: <scp>IgG4</scp>‐related vasculitis

Immunoglobulin-G4 (IgG4)-related disease is essentially a fibro-inflammatory disease that can affect any organ simultaneously or at different times. The disease usually presents with organ growth that mimics a tumour and can affect the lacrimal glands, major salivary glands, pancreas, bile ducts, retroperitoneal area, lungs, kidneys, aorta, meninges and thyroid gland. The immunopathogenesis behind this new disease has not yet been elucidated. Histopathological distinguishing features of the disease include dense lymphoplasmocytic infiltrates dominated by IgG4 positive plasma cells, storiform fibrosis and obliterative phlebitis. The likelihood of developing with immunoglobulin G4 (IgG4-RD) is a recently identified rare systemic fibroinflammatory disease with an estimated incidence of less than 1 in 100,000 people worldwide. We present our case, which was diagnosed with IGG4-related vasculitis by lung fine needle aspiration biopsy, which is very rare in the literature.