IgG4-Related Disease of Genitalia: When Inflammation Imitates Cancer

The systemic fibro-inflammatory disease known as immunoglobulin G4-related disease (IgG4-RD) usually shows multiorgan involvement. A unique instance of a solitary IgG4-RD of the epididymis in a male adult, age 54, was reported. A painless mass over the lower aspect of the left testicle was his initial presentation. Tuberculosis was diagnosed based on the clinical findings. A comparatively hetero-echoic mass lesion on the left epididymis near the left testis was visible on the scrotum ultrasound. The patient was planned for surgical removal of the epididymal mass. However, intraoperative findings showed the mass was tightly stuck to the left testicle and indivisible from it, which required left total orchiectomy. The histopathology showed that the number of plasma cells and keloid-like collagen was increased along with focal spindle cell proliferation. Vimentin and IgG4 immunohistochemistry were positive, while CD34 was negative. IgG4 was high in the serum (165 mg/dL). There was no evidence of systemic involvement on the abdomen or thorax computed tomography. IgG4-RD of the epididymis was diagnosed and validated by immunohistochemistry and histopathology with high blood IgG4 levels. The medical literature only reports a very small number of solitary cases of IgG4-RD of epididymis with no other systemic manifestations. This study highlights the significance of this rare inflammatory condition mimicking epididymal tuberculosis or testicular malignancy.