Current clinical and therapeutic approach to tumour-like mass lesions in granulomatosis with polyangiitis.

Granulomatosis with polyangiitis (GPA) is a systemic autoimmune disorder classified among the anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and characterized by a triad of upper and lower respiratory tract disease, systemic vasculitis involving small-to-medium vessels and renal manifestations. Mass lesions, also described as inflammatory lesions, pseudotumor or tumour-like masses, are uncommon manifestations of GPA and are often called granuloma since histology examination shows granulomatous inflammation and rarely vasculitis. Masses could represent a localized manifestation of GPA or develop as part of a systemic disease. Unusual clinical presentation together with nonspecific radiological and histological features may delay the correct diagnosis leading to disease progression and organ damage. Diagnosis of GPA in such cases may be challenging and malignancy or infections must be considered as alternative diagnostic options. Here we reviewed all the different sites where mass lesions were reported in GPA, focusing on atypical localization, and summarized current therapeutic options and their different outcomes. We retrieved and discussed the cases reported since 2010, bearing in mind the advances in the therapeutic management of AAV patients in the last decade, namely biological therapy such as rituximab. Despite treatment regimens with glucocorticoids and immunosuppressive agents, mass lesions have a refractory course in a high proportion of patients. Invasive surgical procedures may be considered only when drug therapy fails.