[850] Immunohistochemical Analysis of Urachal Carcinoma (UC) with Emphasis on Its Morphologic Types and Their Differential Diagnosis with Metastatic Colonic Adenocarcinoma (CAC): Diagnostic Role of Traditional and Novel Markers
GP Paner, JK McKenney, JL Yao, WL Frankel, SS Shen, RE Jimenez. Loyola University Medical Center, Maywood, IL; The Mayo Clinic, Rochester, MN
Background: The vast majority of UC is urachal adenocarcinoma (UAC) which has several morphologic types including mucinous, colloid, enteric, not otherwise specified (NOS), mixed, and signet ring cell (SRC) types. Metastatic carcinomas from various sites can often mimic these different UAC types; such as the enteric and SRC types by those arising from the colon. However, the immunophenotypic data pertaining to UC and its morphologic types that may potentially aid in their distinction is very limited.
Design: We examined 24 bona fide UCs including 23 UACs (8 mucinous/colloid, 8 enteric, 1 NOS, 3 mixed and 3 SRC types) and 1 urachal urothelial carcinoma (uroCa) with glandular differentiation, and 5 bladder metastasis of CAC including 1 with SRC carcinoma (SRCC) differentiation. Non-urachal type bladder and equivocal UAC cases were excluded. Whole sections for all cases except for 1 from TMA were immunostained with the ff: p63, CK7, CK20, CDX2, 
-catenin, claudin-18 and REG IV.
Results:
| Histology | p63 | CK7 | CK20 | CDX2 | Nuclear -catenin | Claudin-18 | REG IV |
| UAC, overall | 0/23 | 13/23 | 23/23 | 17/23 | 0/23 | 9/22 | 18/23 |
| UAC, mucinous/colloid | 0/8 | 5/8 | 8/8 | 7/8 | 0/8 | 2/7 | 7/8 |
| UAC, enteric | 0/8 | 6/8 | 8/8 | 6/8 | 0/8 | 2/8 | 5/8 |
| UAC, NOS | 0/1 | 1/1 | 1/1 | 0/1 | 0/1 | 0/1 | 0/1 |
| UAC, mixed | 0/3 | 0/3 | 3/3 | 3/3 | 0/3 | 2/3 | 3/3 |
| UAC, SRC | 0/3 | 1/3 | 3/3 | 1/3 | 0/3 | 3/3 | 3/3 |
| Urachal UroCa | 1/1 | 1/1 | 1/1 | 0/1 | 0/1 | 0/1 | 0/1 |
| Metastatic mod diff CAC | 0/5 | 1/5 | 5/5 | 5/5 | 4/5 | 0/5 | 0/5 |
| Metastatic colonic SRCC | 0/1 | 0/1 | 1/1 | 1/1 | 1/1 | 1/1 | 1/1 |
All UACs, urachal uroCa, and CACs showed membranous
-catenin positivity. p63 highlighted benign urachal remnants intermingled with neoplasm in 5 UCs.Conclusions: 1) UC does not express nuclear
-catenin in sharp contrast to metastatic CAC. 2) Expression of CK7 and REG IV is higher in enteric type UAC compared to differentiated CAC. Thus, -catenin, CK7 and REG IV may potentially aid in this morphologic differential diagnostic context. 3) In addition to the enteric type UAC, CDX2 can also be expressed with high frequency by UACs with no obvious enteric morphology. 4) The novel colonic SRCC selective markers claudin-18 and REG IV can also be expressed by SRC type UAC. 5) Although not expressed by UAC, p63 may highlight intermingled benign urachal remnants within the neoplasm.Category: Genitourinary (including renal tumors)
Wednesday, March 11, 2009 9:30 AM
Poster Session V # 109, Wednesday Morning