[1655] Mucinous Carcinoma (MC) of the Gallbladder (GB): Clinicopathologic Analysis of 14 Cases Identified among 606 GB Carcinomas

O Tapia, JC Roa, A Cakir, N Dursun, I Coban, O Basturk, J Cheng, J Sarmiento, H Losada, NV Adsay. U de La Frontera, Temuco, Chile; Emory U, GA; NYU, NY

Background: There is virtually no data in the literature regarding the incidence, subtypes & clinicopathologic characteristics of MC of GB.
Design: 606 primary invasive GB carcinomas were reviewed. Extracellular mucin production of variable degrees & patterns was identified in 40(6%). Those with >50% of the tumor showing stromal mucin deposition (14 cases, 2.3%) were classified as MC. Remainders (26 cases, 3%) were excluded as adenocarcinoma with focal mucinous differentiation.
Results: Clinical: Mean age=64. F/M=1.6 (vs 3.8 of usual GB carcinomas; UCa). Pathology: Mean & median tumor sizes were larger than those of UCas (4.8 & 3.4 vs 2.7 & 2.4 cm, respectively; p=0.034). MCs revealed 3 histologic patterns: I.Colloid(2/14): >90% composed of well-defined stromal mucin nodules, some containing scanty ca cells, mostly floating within the mucin. II.Mixed-mucinous(7/14): Substantial amount (up to 50%) of other Ca component in addition to at least 50% mucinous pattern. III.Mucinous signet-ring cell(5/14): Both the cells within the mucinous component and those infiltrating into the stroma (individually or in cords) are mostly of signet-ring morphology. 3/14 MCs were associated with an intramucosal papillary neoplasm of villous-intestinal pattern. IHC: MCs lacked the gastric-pancretobiliary differentiation marker(MUC6) and some of the intestinal differentiation markers(CDX2/CK20); although colloid marker(MUC2) was expressed.

CK7	CK20	MUC1	MUC2	MUC5AC	MUC6	CDX2	p53
4/7	2/7; F	3/7	6/7	6/7	0/7	1/7 F	3/7 (1; F)

F:Focal

MLH1 and MSH2 was retained in all 7 tested. Outcome: F/U was available in 11: 10 died of disease (1-37 mos), 1 was alive (23 mos). Median survival was worse than that of UCas (13.7 vs 49.8 mos); however, the difference in estimated survival probabilities was not significant, due to small number of MCs (p=0.09).
Conclusions: Focal/aberrant mucinous differentiation is noted in 6% of GB carcinomas; however, MCs (defined as >50% with stromal mucin) constitute 2.3% and typically present as large tumors. Most are mixed type (not pure colloid), which goes along with their aggressive behavior; their prognosis appears to be even worse than usual GB carcinomas. Immunophenotypically, they are different from usual GB carcinomas by MUC6 negativity, from intestinal carcinomas by an inverse CK7/20 profile, and pancreatic MCs by CDX2 negativity. Unlike gastrointestinal MCs, they appear to be microsatellite stable.
Category: Liver & Pancreas

Monday, March 22, 2010 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 215, Monday Morning