Diagnosing seminoma: practicalities and problems

Abstract

Classical seminoma is the most commonly encountered testicular neoplasm. Most clinically localised seminomas are now managed by surveillance, though adjuvant chemo or radiotherapy can be given. The diagnosis of seminoma can be relatively straightforward, but may present unforseen challenges leading to inappropriate treatment or serious misdiagnosis in a number of ways. 1) Thorough macroscopy. Seminomas require rigorous blocking. This is because tiny amounts of non-seminoma may be missed, leading to potential under-treatment. Inflammatory lesions and granulomatous lesions may also harbour small foci of seminoma and should be treated with suspicion. 2) Unusual histological patterns. Some seminomas show unusual features. They may show frequent syncytiotrophoblastic cells leading to misdiagnosis as choriocarcinoma. A minority show tubular elements or even signet ring change. 3) Mimicks. Solid type yolk sac tumour may mimic seminoma as well as a number of other entities, especially some malignant sex cord stromal tumours. The former should be considered for adjuvant treatment, while the latter may require a prophylactic retroperitoneal lymph node dissection. Spermatocytic seminoma, especially when monomorphic may be mistaken for seminoma. Close morphological inspection allied to to judicious use of immunochemistry and knowledge of clinical details including serology is essential for the accurate diagnosis of seminoma.