Idiopathic granulomatous orchitis (IGO) is a rare inflammatory disorder of the testis of unknown etiology.
Clinical features:
(1) testicular pain
(2) variable fever
(3) testicular mass that is suspicious for malignancy
Ultrasound shows an enlarged, diffusely hypoechoic testis or focal hypoechoic areas. There typically is no rim of residual normal testis; if a rim of normal testis is seen then another diagnosis should be considered.
MRI shows a homogeneous hypointense mass or multiple hypointense areas on T2-weighted images with variable degrees of enhancement.
Histologic features:
(1) epithelioid granulomatous reaction involving the seminiferous tubules and interstitium
(2) interstitial lymphoplasmacytic inflammation
(3) variable interstitial fibrosis
The diagnosis requires exclusion of other conditions:
(1) tuberculosis
(2) sperm granulomas
(3) deep fungal infection
(4) xanthogranulomatous orchitis
(5) IgG4-related orchitis
(6) intratubular germ cell neoplasia unclassified with a granulomatous reaction
(7) malakoplakia
