GATA3-Positive Adnexal Adenocarcinoma: Report of a Confusing Case with a Potential Pitfall of Leading to a Misdiagnosis of Urothelial Carcinoma and a Review of Published Work.

We describe a confusing case of GATA3-positive adnexal adenocarcinoma with a potential pitfall of leading to a misdiagnosis of urothelial carcinoma. A 62-year-old male presented with a subcutaneous nodule on the right lower abdomen around a scar from surgery for urothelial carcinoma in the right urinary tract, which had been resected 8 years previously. Histologically, atypical cells possessing ample cytoplasm and partial intracytoplasmic lumens were densely grouped in the subcutaneous expansive nodule and bilateral inguinal lymph nodes dissected. Decapitation secretion could not be seen. Neoplastic cells were positive for CK7, GATA3, and GCDFP15, and negative for CK5/6, CK20, p63, CD10, PAX8, HER-2, and uroplakin-II. Neoplastic cells in the urothelium and the metastasized lung were positive for CK7, CK5/6, and GATA3, and negative for CK20, p63, GCDFP15, and TTF-1. A variable level of GATA3 expression in malignant tumors with apocrine and eccrine differentiation should be recognized by dermatologists.