Aims First, to determine the frequency of intravascular granulomas (IVGs) in seminomas and assess for the presence of entrapped seminoma cells. Second, to identify the relationship of this unusual form of vascular space invasion with tumour relapse and/or dissemination.

Methods 86 cases of seminoma were reviewed to identify IVGs. Immunostaining for OCT3/4 and CD68 was performed. Pathological stage, presence of conventional vascular and rete testis invasion, parenchymal granulomas and follow-up were recorded. Multivariable analysis incorporating tumour size, vascular invasion (conventional granulomas and IVGs) and rete testis invasion was performed.

Results IVGs were identified in 13 cases (13/86). CD68 confirmed histiocytes in all cases. OCT3/4 identified tumour cells in 9/13 seminomas. 27 patients had disease progression with either dissemination at presentation (n=11) or relapse (n=16). Of these 27 patients, 8 had IVG (29.6%). By comparison, 6 of 57 clinical stage 1 seminomas that did not relapse had IVG (10.53%). Multivariable analysis revealed that no single parameter was statistically significant at predicting tumour relapse and/or dissemination (size: HR 1.65; CI 0.71 to 3.82, p=0.24, rete testis invasion: HR 1.04; CI 0.48 to 2.26, p=0.92, lymphovascular space invasion/IVG: HR 1.62; CI 0.65 to 4.01, p=0.30).

Conclusions IVGs may represent a previously unrecognised form of vascular space invasion in seminomas. Studies on larger cohorts are needed to demonstrate its clinical value.