Introduction:
Microscopic polyangiitis (MPA) is an antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) that can affect any organ. Sometimes, untypical localization, together with an unusual clinical manifestation of tumour-resembling inflammatory changes, can cause a delay in diagnosis and proper treatment.

Aim:
The aim of this study was to expose the case of very rare location of MPA manifestation.

Case study:
In this paper, we present the case of inflammatory testicular tumour-like lesion that was a manifestation of MPA and mimicked testicular cancer.

Results and discussion:
It is probably first desribed case of MPA mimicking testicular cancer. However, in the literature some others AAV manifestation in that location can be found. In these patients orchiectomy was recommended much more often than a testicular biopsy.

Conclusions:
We conclude that in case of a patient with untypical features of a tumour, inflammatory processes, including vasculitis, should be taken into consideration in differential diagnosis.