CGH analysis of a rare case of squamous cell carcinoma of the urachus of the bladder. W. Thelmo¹, M.J. Macera^2,3, J. Breshin^2,3, P. Chandra³, A. Babu^2,3. 1) Dept Pathology; 2) Div Molec Medicine & Genetics; 3) Dept Medicine, Wyckoff Heights Med Ctr, Brooklyn, NY.
   A seventy two year old female was admitted for gross hematuria. She has a history of hypertension, asthma and urinary reflux. She denied dysuria or increase of urinary frequency. She had no weight loss, fever, chills, nausea or vomiting or a history of passing out stones in the urine. She is a non-smoker. She underwent cystoscopy and urinary bladder biopsy which showed high grade urotherlial carcinoma with necrosis. Three weeks later, this was followed by radical cystectomy and ileal conduit. There was a tumor in the dome of the bladder with ulceration demonstrating squamous cell carcinoma with invasion of the urachal remnant. The rest of the bladder showed chronic cystitis, diffuse without squamous metaplasia or any evidence of parasites (Schistosoma). Right and left pelvic lymph nodes were all negative for tumor. Comparative genomic hybridization (CGH) analysis was done on DNA extracted from formalin fixed tumor and identified loss of a chromosome 17 as well as the entire 16p arm. The UroVysion probe was then applied to sections of the tumor. Three abnormal clones were detected: one with a single 17 centromere and a single p16 gene (located at 9p21) (27.0%), the second with a single 17 centromere and two p16 genes (17.0%), and the third with two 17 centromeres and a single p16 gene (25.0%). The remaining cells (31.0%) showed normal signal numbers for all probes. No loss of 9p was seen by CGH, likely due to a small deletion below the detection level of the test. Deletions of part of or loss of the entire chromosome 9 are the most common findings in all bladder cancers. Loss of chromosome 17 has been associated with progression in this disease. Only approximately 7% of non schistosome related bladder cancer is squamous cell, and aberrations of chromosome 17 and loss of 16p are more frequently observed in transitional cell carcinoma than squamous cell carcinoma. This case represents an unusual presentation and further study may help to elucidate this complex disease.