Intrahepatic mucinous cholangiocarcinoma

Dear Editor,

Mucinous cholangiocarcinoma (MC) is an exceptionally rare variant of intrahepatic cholangiocarcinoma, which comprises a large amount of mucin. ¹ , ² , ³ , ⁴ Here, we report a case of resected MC of the liver.

A 56‐year‐old male patient came into the Emergency Department due to fever and epigastralgia; initial computed tomography (CT) scans revealed a cystic lesion in the S2 segment of liver (Figure 1A) with marked dilated intrahepatic ducts (IHDs) and extrahepatic ducts (EHDs). Abdominal magnetic resonance imaging (MRI) revealed the lobulated lesion, much similar to bile juice or other cystic content, showed prominent hyperintensity on T2‐weighted and hypointensity on T1‐weighted images. There were no overt enhanced soft tissue components observed on the post‐enhanced T1‐weighted images. Biliary cystadenoma was impressed at that time, and the primary physician treated the patient with endoscopic retrograde biliary drainage stent placement.

FIGURE 1.

Images and pathologic studies of liver tumor. A, Enhanced computed tomography showed a cystic lesion in the left hepatic duct with marked dilated IHDs and EHDs. B, Sixteen months later, enhanced CT showed the development of a poorly enhanced, lobulated cystic tumor with septi in the left hepatic lobe. C, Sixteen months later, MRI showed that the lobulated malignant neoplasm had a high signal on the T2‐weighted images in the left hepatic lobe. D, Initial fistulography showed dilated intrahepatic bile ducts of left hepatic lobe. E, Resected liver specimen of the left hepatic lobe. F‐G, Microscopically eosinophilic neoplastic cells with abundant mucin production replaced the normal liver parenchyma and were arranged in papillary or tubular structures Hematoxylin and eosing (HE) staining. Original magnification: ×20 and ×200. H‐K, By immunohistochemistry, the tumor cells were positive for MUC 2, MUC5AC, MUC 6, and CK 7. Original magnification: ×200. CK, cytokeratin; CT, computed tomography; EHDs, extrahepatic ducts; IHDs, intrahepatic ducts; MRI, magnetic resonance imaging; MUC, mucin core protein

However, 16 months later, he came back to our Emergent Department with similar symptoms and signs. Emergent‐enhanced CT revealed enlargement of the previously identified multilobulated cyst lesion, which now occupied the entire left hepatic lobe. The lesion had irregular margins, demonstrated poor enhancement, and caused the dilatation of the common bile duct and bilateral IHDs (Figure 1B). Repeated MRI showed the previously recognized distinct high signal on the T2‐weighted images (Figure 1C). There were also clusters of metastatic lymphadenopathies along the hepatoduodenal and gastrohepatic ligaments and at cardiophrenic, aortocaval, and paraaortic regions, which exhibited similar high signals on T2‐weighted and diffusion‐weighted images (DWI) images. Fistulography validated that the lesion was located in the intrahepatic ducts (Figure 1D).

Palliative left lobectomy was carried out for the patient. The macroscopic examination found a mucous lobulated tumor that occupied most of the left hepatic lobe (Figure 1E) with size: 18.8 × 13.2 × 6.0 cm. The resected liver specimen had whitish and lobulated cutting surface, and mucinous content surrounded by a grossly distinct capsule. Microscopic examination showed glandular and tubular structures with mucin production occupying its background. The tumor cells were characterized with low‐to‐moderate nuclear‐cytoplasmic ratio (Figure 1F‐G), which indicated a low‐grade mucinous carcinoma.

Immunohistochemical analysis revealed positive immunoreactivity in MUC2, MUC5AC, MUC6, CK7 (Figure 1H‐K) irrespective of negative results in MUC1. CK20 survey was negative, whereas CDX2 stain only showed focal and faint positive in tumor cells. Esophagogastroduodenoscopy and coloscopy showed no evidence of gastrointestinal lesions. No abnormal uptake of gastrointestinal tracts was depicted on fluorodeoxyglucose (FDG)‐positron emission tomography (PET). Therefore, we categorized this tumor as a MC, an extremely rare variant of intrahepatic cholangiocarcinoma.

In conclusion, the probability of MC should be taken into consideration even when there might not be any prominent enhanced soft tissues on imaging modalities. This scarce primary intrahepatic MC was confirmed by the expression of specific mucin core proteins such as MUC1, MUC2, MUC4, MUC6, and MUC5AC, ⁵ and by the exclusion of metastatic mucinous carcinoma from colorectal cancer or breast cancer.

CONFLICT OF INTEREST

The authors declare no potential conflict of interest.