The findings suggest a possible role for ultraviolet radiation and chronic immunosuppression in the induction of malignant squamous differentiation in a subset of EPCs. Further reports on this histological variant of EPC are required to determine whether a pathogenetic link does indeed exist or whether these tumours simply represent a unique variant of squamous cell carcinoma with divergent acrosyringial differentiation.

Objective To systematically review the literature on the prognostic value of lymphovascular invasion (LVI) and embryonal carcinoma (EC) for occult metastatic disease in clinical stage I nonseminomatous germ cell tumour (CS I NSGCT). Materials and methods The PubMed, Embase (OVID) and SCOPUS databases were searched up to March 2019. Studies reporting on the association between LVI and/or EC and occult metastatic disease were considered for inclusion. The quality and risk of bias were evaluated by the Quality in Prognosis Studies tool. Results We screened 5287 abstracts and 207 full‐text articles. We included 35 studies in the narrative synthesis and 24 studies in a meta‐analysis. LVI showed the strongest effect. Pooled rates of occult metastasis were 47.5% and 16.9% for LVI‐positive and LVI‐negative patients, respectively (odds ratio [OR] 4.33, 95% confidence interval [CI] 3.55–5.30; P < 0.001). Pooled rates of occult metastasis were 33.2% for EC presence and 16.2% for EC absence (OR 2.49, 95% CI 1.64–3.77; P < 0.001). Pooled rates of occult metastasis were 40.0% for EC >50% and 20.0% for EC <50% (OR 2.62, 95% CI 1.93–3.56; P < 0.001). Conclusions LVI is the strongest risk factor for relapse. The prognostic value of EC is high, but there is no common agreement on how to define this risk factor. Both EC presence and EC >50% have similar ORs for occult metastasis. This shows that the assessment of EC presence is sufficient for the classification of EC.

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