3. Clear cell adenocarcinoma of urinary tract: 2 cases involving urethra and bladder

Abstract

<h3>Background</h3> Adenocarcinoma of urothelial tract is considered primary when conventional urothelial carcinoma component is not identified. Cases with co-existing urothelial carcinoma are regarded as differentiation of urothelial origin. Clear cell adenocarcinoma is a rare variant that needs to be discriminated from primary adenocarcinoma of urinary tract, urothelial carcinoma with glandular differentiation and metastatic tumours. <h3>Methods</h3> We report two cases of clear cell adenocarcinoma of urinary tract, involving urethra (Case 1) and urinary bladder (Case 2). Histological features, immunohistochemical profile and clinical outcome are summarised. <h3>Results</h3> Case 1 (urethral tumour): A 64-year-old Chinese female presented with anterior vaginal wall mass. Biopsy showed clear cell adenocarcinoma and she underwent neoadjuvant chemotherapy. Resection showed urethral tumour involving bladder neck and one lymph node. Histologically, tumour showed tubulopapillary and glandular architecture, hobnail nuclei and clear cytoplasm. Immunohistochemically, tumour cells were CK7 and CA125 positive, thrombomodulin and HMWCK weak positive, and CK20 and p63 negative. Patient is under follow-up. Case 2 (bladder tumour): A 56-year-old Chinese female underwent surgery for bladder mass. Tumour showed tubulopapillary and glandular architecture, hobnail nuclei and clear cytoplasm. Two lymph nodes were positive. Immunohistochemical profile was CK7 positive and CK20 negative. Patient expired following peritoneal carcinomatosis. Conclusions: Clear cell adenocarcinoma of urinary tract can be identified by a constellation of features: (1) presence of tubulo-papillary/glandular architecture, high grade hobnail nuclei and clear cytoplasm, (2) absence of primary adenocarcinoma of urinary tract, conventional urothelial carcinoma with glandular differentiation and metastasis, and (3) immunohistochemical profile of positive CK7 and CA125, weak positive HMWCK and CK5/6, negative CK20 and p63 and negative staining for potential metastatic tumour (e.g., CDX2 negative). Clinical behaviour is aggressive. Correct identification can aid in trial of neoadjuvant chemotherapy.