[1705] Mucinous Hepatocelluar Carcinoma: A Previously Undescribed Variant of Hepatocellular Carcinoma

Safia N Salaria, Michael S Torbenson. Johns Hopkins School of Medicine, Baltimore, MD

Background: Mucin production in a primary liver cancer generally provides evidence for a diagnosis of cholangiocarcinoma or a biphenotypic carcinoma with mixed hepatocellular and cholangiocarcinoma differentiation. We describe four cases of a unique subtype of hepatocellular carcinoma, one that shows unequivocal hepatocellular differentiation, but produces pools of extracellular mucin and has no evidence for glandular or biliary differentiation.
Design: The surgical pathology files were searched for cases of hepatocellular carcinoma with extracellular mucin production. All cases of cholangicocarcinoma and all cases of biphenotypic hepatocellular/cholangiocarcinoma were excluded.
Results: Four cases were identified (three resections, one biopsy). Three were consult cases submitted because of the unusual extracellular mucin production. All were male patients and two had chronic hepatitis C, one had no known liver disease, and information was not available in the fourth case. The median age was 49 years (range 34-83 years). Three of the patients (75%) were Caucasian and one was Middle Eastern in ethnicity. The median tumor size was 5.8 cm (range 3.3-12 cm) and tumors were single in two cases and multifocal in one case; one case did not have information available. The tumors were well differentiated in all cases, with cells growing in a trabecular architecture and showing typical hepatocellular morphology with abundant eosinophilic cytoplasm and only mild cytological atypia. However, the tumors were also striking for large pools of extracellular mucin that separated the trabecular plates. No intracellular mucin was seen. No gland formation or psuedogland formation was seen. The mucin was alcian blue positive in all cases and mucicarmine positive in 2 of 4 cases. All cases were negative for lymphovascular invasion. By immunohistochemistry, the tumors were Hep Par positive and showed a typical canalicular staining pattern for CD10 or pCEA staining. Ki-67 immunostains showed mildly increased proliferative rates. CK19 immunostains (typically positive in cholangiocarcinomas) were negative. The background livers in the resected specimens showed portal fibrosis (N=2) and cirrhosis (1).
Conclusions: We report a previously undescribed subtype of hepatocellular carcinoma: mucinous hepatocullar carcinoma. These hepatocellular carcinomas show striking extracellular mucinous production, but lack glandular or biliary differentiation. Recognition of the unique histopathological findings will allow pathologists to properly diagnosis this unique variant of hepatocellular carcinoma.
Category: Liver

Tuesday, March 5, 2013 9:30 AM

Poster Session III # 191, Tuesday Morning

 

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