Glutathione sulfhydryl transferase (GST) is believed to play a major role in the detoxification of chemotherapeutic agents and therefore is thought to be important in chemoresistance. Thirty primary testicular germ cell tumors were stained immunohistochemically for GST pi using a rabbit polyclonal antibody and formalin-fixed paraffin-embedded tissue. There were 12 pure seminomas and 18 mixed germ cell tumors (GCTs). Immunostaining of each element present was graded as negative (-), weakly positive (+), or strongly positive (++). The results were as follows: seminoma (8/17 +, 9/17 ++); embryonal carcinoma (1/13 -, 7/13 +, 5/13 ++); mature teratoma (9/9 ++); immature teratoma (7/7 +); endodermal sinus tumor (7/8 +, 1/8 ++); and choriocarcinoma (1/1 -). These results show that variability exists in the expression of GST pi between different tumor types and between different examples of the same tumor type. Strongest expression was seen in seminomas and mature teratomas while other germ cell elements tended to show weaker staining. The staining patterns showed no apparent correlation with stage or response to therapy.

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