Paratesticular fibrous pseudotumor with histological features of IgG4-related disease: two case reports and review of the literature.

Background: Paratesticular fibrous pseudotumor (PFP) is a rare intrascrotal benign fibrous mass of uncertain aetiology, usually arising between testicular tunica layers and is supposed to be related to inflammatory reactive conditions. Because of morphological similarities to IgG4-related sclerosing fibro-inflammatory lesions, some authors recently postulated that PFP might belong to the IgG4-related disease (IgG4-RD) family. Considering the rarity of this lesion, only few cases have been reported in literature about the correlation between IgG4-RD and PFP. Management of PFP could be extremely challenging: due to the lack of typical clinical signs and the non-specific radiological characteristics, misapprehension does occur in the majority of cases, mainly because these intrascrotal mass may mimic testicular neoplasm, therefore leading to radical orchidectomy rather than a desirable testis-sparing surgery.

Case Description: Herein we report two cases of young males treated for PFP with histological feature of IgG4-RD. Patients underwent testicular sparing surgery. At 2-year follow-up no evidence of local or distant relapse nor testicular disorder was observed in both patients. An up-to-date review of the literature about the correlation between PFP and the IgG4-RD was carried out.

Conclusions: PFP is an extremely rare condition with uncertain etiology being part of IgG4-RD family. Preoperative imaging mimics malignancy hence diagnosis is usually made by specimen analysis. Intraoperative frozen section is fundamental in order to guarantee conservative treatment that is feasible and safe after mid-term follow-up.