A Case of Transient Spontaneous Regression of Intrahepatic Cholangiocarcinoma Clinically Mimicking Inflammatory Pseudotumor: A Diagnostic Dilemma.

introductionSpontaneous regression of intrahepatic cholangiocarcinoma (iCCA) is extremely rare and may create diagnostic confusion when mimicking benign inflammatory lesions. We herein report a case of iCCA that demonstrated transient spontaneous regression, which led to difficulty in differentiating it from hepatic inflammatory pseudotumor (HIPT). CASE PRESENTATION: A 70-year-old woman with alcoholic liver cirrhosis was found to have a 14-mm hepatic mass in segment 6 with peripheral ring-like enhancement on contrast-enhanced CT and high fluorodeoxyglucose (FDG) uptake (maximum standardized uptake value [SUVmax] 11.2). Carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) were mildly elevated. iCCA, hepatocellular carcinoma, and combined hepatocellular-cholangiocarcinoma were considered. Two months later, the lesion regressed spontaneously to 5 mm without treatment, and CEA and CA19-9 decreased, suggesting a diagnosis of HIPT. However, the lesion gradually increased in size over the following year. CEA and CA19-9 subsequently increased markedly, and FDG uptake intensified (SUVmax 14.3). Given the strong suspicion of malignancy, laparoscopic partial hepatectomy was performed. Histopathological examination revealed an invasive iCCA with glandular formation, mucin production, necrosis with neutrophilic infiltration, and portal vein invasion.

conclusionsThis case highlights that spontaneous tumor regression does not exclude malignancy. Careful long-term surveillance and timely surgical intervention are crucial when imaging findings and tumor marker trends raise suspicion of malignancy despite temporary regression.