Paratesticular fibrous pseudotumor in young males presenting with histological features of IgG4-related disease: two case reports

INTRODUCTION: Paratesticular fibrous pseudotumors represent benign new growths confined to intrascrotal structures. Both pathogenesis and clinical management are little understood due to the rarity of the lesion, with less than 200 cases reported to date. Recently, paratesticular fibrous pseudotumors have been postulated to be immunoglobulin G4-related, pathogenetically. Here we report two cases of patients with paratesticular fibrous pseudotumor to highlight the clinical features of this rare disease and we report the immunohistochemical examinations to support the theory of paratesticular fibrous pseudotumor being an immunoglobulin G4-related disease. CASE PRESENTATIONS: A 28-year-old white man presented with a painless intrascrotal mass. After a clinical examination, a malignant growth was suspected. His ultrasound results revealed a well-demarcated hypoechoic lesion of 1.5cm in diameter at the spermatic cord. Our patient underwent local excision. His follow-up has been uneventful for 12 years. The second case was an 18-year-old white man who presented with a painless scrotal mass suspicious of testicular tumor. A magnetic resonance imaging scan revealed a 3cm mass at the spermatic cord with very low signal density on T2-weighted imaging and a low and inhomogeneous uptake of gadolinium contrast agent on T1-weighted, fat-suppressed imaging. Following local excision, our patient has been well for 18 months. On histological examination, both of the lesions consisted of collagen-rich hyalinized fibrotic tissue with storiform features. There were lymphofollicular infiltrates and, sporadically, also venulitis. The immunoglobulin G4 staining (in case 2) showed an infiltrate of 10 to 15 positive cells per high-power field on average, corresponding to a proportion of 40% in evaluable hot spots. The two patients with paratesticular fibrous pseudotumor presented within a time span of 15 years. During that time, 400 patients with testicular germ cell tumors had been treated in our institution. CONCLUSIONS: The specific histological features documented in our case lend support to the theory of paratesticular fibrous pseudotumor being an immunoglobulin G4-related sclerosing disorder. Paratesticular fibrous pseudotumors usually occur in young adulthood. Clinically, paratesticular fibrous pseudotumor can mimic testicular malignancy. Ultrasonographic findings are largely unspecific, however, scrotal magnetic resonance imaging may aid in discriminating the lesion from malignant tumors. Local excision, whenever technically feasible, is the preferred treatment of paratesticular fibrous pseudotumor.