Concurrent IgG4-Related disease and clear cell renal cell carcinoma

We report a case of a 54-year-old man with a concurrent diagnosis of IgG4-related disease (IgG4-RD) and clear cell renal cell carcinoma (ccRCC) following asymptomatic submandibular lymphadenopathy with an incidental finding of a left renal mass. Partial nephrectomy revealed ccRCC with surrounding lymphoplasmacytic infiltrate, storiform fibrosis and a strong positivity for IgG4 on immunoperoxidase staining. The IgG4+:IgG + ratio was >40% and serum IgG4 levels were elevated at 159mg/dL. This case highlights the concurrent diagnosis of a unique dual pathology within the same organ and emphasises the importance of malignancy screening in patients with IgG4-RD and vice versa.