The role of OCT4 immunohistochemistry in evaluation of retroperitoneal lymph node dissections: a pilot study

We investigated the role of OCT4 immunohistochemical staining in detecting germ cell tumor lymph node metastases. Retroperitoneal lymph node dissection is important for staging and treatment of testicular germ cell tumors, and OCT4 is sensitive and specific for pluripotent testicular germ cell tumors; however, micrometastases, particularly from seminoma, can be difficult to detect. We examined 262 lymph nodes in 45 retroperitoneal lymph node dissection specimens from germ cell tumor patients. Specimens were categorized as postchemotherapy and untreated retroperitoneal lymph node dissection with or without clinical suspicion, based on lymphadenopathy or elevated serum germ cell tumor markers. Sections were stained with anti-OCT4 antibody. Twenty-one additional positive lymph nodes in 12 cases were detected to harbor scattered seminoma cells, singly and in small clusters, from 256 previously considered benign in: untreated retroperitoneal lymph node dissection with clinical suspicion (13% increase), postchemotherapy retroperitoneal lymph node dissection (7%), and untreated retroperitoneal lymph node dissection without suspicion (4%). However, no patient with an entirely negative dissection specimen was reclassified as positive. OCT4 immunohistochemistry detected scattered seminoma cells and small clusters of seminoma cells in lymph nodes previously considered to be benign for an overall increase of 8%, greatest in the setting of untreated retroperitoneal lymph node dissection with clinical suspicion. However, immunohistochemistry did not convert any entirely negative specimen to positive. Future studies will be useful to determine whether the small volume of disease detected by immunohistochemistry has the same impact as routinely detected lymph node metastases.