What Is ICC Cancer? Intrahepatic Cholangiocarcinoma

Intrahepatic cholangiocarcinoma, commonly abbreviated ICC or iCCA, is a cancer that starts in the bile ducts inside the liver. It belongs to a broader family of biliary cancers but behaves as a distinct disease with its own risk factors, molecular features, and treatment landscape. ICC is uncommon compared to liver cancers that arise from liver cells themselves, but its incidence has been climbing worldwide over the past few decades, and it remains one of the more difficult gastrointestinal cancers to treat. The good news is that advances in molecular profiling and targeted drugs have opened new options that did not exist even a few years ago.

Where ICC Fits Among Biliary Cancers

Biliary cancers arise from the cells lining the bile ducts, the network of tubes that carry bile from the liver to the small intestine. They are split into three groups based on location: intrahepatic cholangiocarcinoma (inside the liver), extrahepatic cholangiocarcinoma (outside the liver, including the perihilar region near where ducts exit), and gallbladder cancer. Although they share a common cell type of origin, each group behaves differently in terms of how aggressive it is, how well it responds to treatment, and how long patients survive.¹

ICC itself is not one uniform disease. Pathologists now recognize at least two major subtypes based on where in the liver’s ductal system the tumor originates. “Large duct” ICC arises from the bigger bile ducts closer to the center of the liver, tends to produce mucin, and often looks and acts more like extrahepatic cholangiocarcinoma. “Small duct” ICC forms in the tiny peripheral ducts and has a different appearance under the microscope, sometimes resembling liver cell tumors enough to cause diagnostic confusion.² This distinction matters because the two subtypes carry different molecular profiles, which increasingly guides treatment decisions.

Animal studies have confirmed that ICC can arise directly from biliary epithelial cells, the lining cells of bile ducts, particularly when chronic inflammation and loss of the tumor-suppressor gene p53 are both present.³ Some evidence also suggests that certain ICC subtypes may originate from liver progenitor cells, which could explain why a subset of these tumors share features with hepatocellular carcinoma.⁴

Rising Incidence and Known Risk Factors

ICC rates have been increasing in most countries tracked between the early 1990s and the early 2010s.⁵ Part of that rise likely reflects better imaging and more precise classification, since tumors that used to be lumped under “liver cancer, not otherwise specified” are now correctly identified as ICC. But the trend is real enough that researchers have looked hard at what drives it.

The risk factors for ICC vary by geography. In East and Southeast Asia, infection with liver flukes, parasitic worms acquired by eating raw or undercooked freshwater fish, is a major driver. The flukes lodge in bile ducts, cause chronic inflammation, damage the duct lining, and alter the local microbiome, all of which promote cancer development over decades.⁶ In Western countries, primary sclerosing cholangitis, an autoimmune condition that scars the bile ducts, carries one of the highest known risks for cholangiocarcinoma.

Beyond those region-specific factors, a range of other conditions raise ICC risk, including viral hepatitis B and C, cirrhosis from any cause, bile duct stones lodged inside the liver, congenital cystic diseases of the biliary system, heavy alcohol use, tobacco smoking, and metabolic syndrome.⁷ Still, the majority of patients diagnosed with ICC in Western countries have none of these recognized risk factors, which makes screening difficult and means the cancer is usually found at a later stage.

How ICC Is Found and Diagnosed

ICC often grows silently for a long time. Symptoms, when they appear, tend to be vague: dull pain in the upper right abdomen, weight loss, fatigue, or sometimes jaundice if the tumor blocks a major bile duct. Because these symptoms overlap with many other conditions, the cancer is frequently discovered incidentally on imaging done for another reason, or it presents when it is already advanced.

CT and MRI are the primary imaging tools. On contrast-enhanced scans, ICC tends to show a pattern of peripheral arterial enhancement with progressive delayed enhancement, reflecting the dense fibrous tissue (desmoplasia) that is a hallmark of these tumors. Newer MRI techniques using liver-specific contrast agents have improved the ability to distinguish ICC from hepatocellular carcinoma, which is important because the two cancers require different treatment approaches.⁸ Several imaging features on CT and MRI, including tumor multiplicity, an infiltrative margin, lymph node involvement, and the pattern of contrast enhancement, also carry prognostic value and help guide surgical planning.⁹

Blood tests play a supporting role. CA 19-9 is the most commonly used tumor marker, but it is not specific to ICC and can be elevated in other biliary and pancreatic conditions. Combining CA 19-9 with CEA improves predictive accuracy for survival after surgery.¹⁰ A recent multi-institutional study found that a scoring system combining all three of CA 19-9, CA 125, and CEA outperformed any individual marker in predicting both overall survival and recurrence-free survival after radical surgery.¹¹ None of these markers are reliable for early detection, though. A definitive diagnosis almost always requires a tissue biopsy or comes from examining the tumor after surgical removal.

Molecular Features That Drive Treatment

One of the most significant developments in ICC care has been the discovery of specific genetic alterations that can be targeted with drugs. The two most clinically relevant are FGFR2 fusions and IDH1 mutations.

About 15% of ICC tumors carry a fusion involving the FGFR2 gene, where part of FGFR2 gets fused to one of more than 60 different partner genes.¹² The result is a permanently activated growth signal. Several FGFR inhibitors have shown meaningful activity in patients whose tumors carry these fusions. Futibatinib, for example, produced responses in about 42% of patients with advanced ICC and FGFR2 fusions, with a median duration of response around 10 months and a median overall survival of roughly 22 months.¹³ Pemigatinib, another FGFR inhibitor, showed durable responses in about a third of patients with FGFR2 rearrangements, with a median progression-free survival near seven months.¹⁴

IDH1 mutations are found in a meaningful fraction of ICC tumors and cause a metabolic abnormality: the mutated enzyme produces abnormally high levels of a metabolite called 2-hydroxyglutarate, which disrupts normal cell differentiation.¹⁵ The drug ivosidenib, designed to block this mutant enzyme, showed a statistically significant improvement in progression-free survival compared to placebo, reducing the risk of progression or death by about 63%.¹⁶

These targeted options exist only for patients whose tumors carry the relevant alteration, which is why molecular profiling through genomic sequencing of a biopsy sample has become standard practice in ICC care. If your tumor does not carry an FGFR2 fusion or IDH mutation, these drugs will not help, and treatment follows a different path.

The Tumor’s Protective Shield

ICC has a reputation for being stubbornly resistant to treatment, and part of the reason lies in its microenvironment. The most common form of ICC, the mass-forming type, builds a thick layer of fibrous tissue around and within the tumor. This desmoplastic reaction is dense with collagen and is populated by cells called cancer-associated fibroblasts, which are the most abundant non-cancer cell type in the tumor’s stroma.¹⁷ These fibroblasts are not passive bystanders. They actively support tumor growth through a web of signaling interactions with immune cells and cancer cells, creating an environment that shields the tumor from the immune system and from chemotherapy.¹⁸

Understanding this microenvironment is an active area of research. If scientists can find ways to disrupt the fibroblast network or make the dense stroma more permeable to drugs and immune cells, it could significantly improve how well existing treatments work. For now, the desmoplastic stroma is one reason ICC responds less dramatically to immunotherapy compared to some other cancer types.

Surgery as the Best Shot at Cure

Complete surgical removal of the tumor, achieving what surgeons call negative margins (no cancer cells at the cut edge), remains the only treatment that offers a real chance of long-term survival. The operation typically involves removing a portion of the liver large enough to encompass the tumor with clear margins, along with any involved bile ducts, blood vessels, or adjacent structures.¹⁹

Whether to remove nearby lymph nodes has been debated for years. A large international study found that patients who turned out to have cancer in their lymph nodes at final pathology lived longer if they had undergone adequate lymph node removal during surgery, with a median overall survival of 28 months versus 23 months without adequate lymph node sampling.²⁰ The benefit was most pronounced in patients without underlying chronic liver disease and in those with earlier-stage tumors. Lymph node dissection also helps with staging, since knowing the true nodal status informs decisions about whether to pursue chemotherapy after surgery.²¹

The unfortunate reality is that most patients are not candidates for surgery at diagnosis, either because the tumor is too large, involves critical blood vessels, has spread to lymph nodes or other organs, or because the patient’s liver function is too poor. Even among those who do undergo resection, recurrence rates are high, with the majority experiencing some form of recurrence within a few years.

Liver Transplantation for Select Cases

Liver transplantation was historically considered off the table for ICC because early results were discouraging. That thinking is shifting. A growing body of evidence suggests that transplantation can produce good outcomes in carefully selected patients: those with small tumors (under about 2 cm) that are unresectable because of underlying liver disease, and those with locally advanced tumors confined to the liver that respond well to chemotherapy or other pre-transplant treatments.²² Patient selection is everything here. Transplanting someone with aggressive or widespread ICC leads to rapid recurrence and wastes a scarce donor organ. But for the right patient, transplant may offer a chance that surgery alone cannot.

Chemotherapy, Immunotherapy, and Combined Approaches

For patients with advanced ICC who cannot undergo surgery, the standard first-line treatment for years was the combination of gemcitabine and cisplatin. The landscape changed with the TOPAZ-1 trial, which showed that adding the immunotherapy drug durvalumab to this chemotherapy backbone improved survival. Updated results showed a median overall survival of about 13 months with durvalumab versus 11 months with chemotherapy alone, and the two-year survival rate roughly doubled, from about 12% to 24%.²³ This combination has become a new standard of care for advanced biliary tract cancers, including ICC.²⁴

A separate large trial, KEYNOTE-966, tested adding pembrolizumab (a different immunotherapy drug) to gemcitabine and cisplatin. Quality-of-life data from that trial are encouraging in one specific sense: adding immunotherapy did not worsen patients’ day-to-day functioning or symptoms compared to chemotherapy alone.²⁵ For patients worried about immunotherapy making them feel worse on top of chemo, that is reassuring.

Locoregional Treatments for Liver-Confined Disease

When ICC stays within the liver but cannot be removed surgically, locoregional therapies delivered directly to the tumor through the liver’s blood supply can be effective. The most studied of these is radioembolization with yttrium-90, where tiny radioactive beads are injected into the artery feeding the tumor, delivering a concentrated dose of radiation from inside.

A phase 2 trial combining radioembolization with chemotherapy as first-line treatment for locally advanced ICC reported a response rate of about 41% and a median overall survival of 22 months, with about a fifth of patients being downstaged enough to undergo successful surgery.²⁶ Another small study using radioembolization combined with gemcitabine, cisplatin, and capecitabine found a median overall survival of 29 months from diagnosis, and more than half the patients were downstaged to surgery.²⁷

A larger registry study of radioembolization alone in cholangiocarcinoma patients reported a median overall survival of 14 months. Patients without cirrhosis fared better, with a median survival of about 19 months compared to 12 months for those with cirrhosis. Serious liver toxicity was relatively uncommon.²⁸ The ability to convert initially unresectable tumors into operable ones through locoregional therapy is one of the more promising developments in ICC management, effectively giving some patients a second path to potentially curative surgery.

Liquid Biopsy and Monitoring Treatment Resistance

Tissue biopsies of liver tumors are invasive and cannot easily be repeated to track how a cancer is evolving during treatment. Liquid biopsy, which analyzes fragments of tumor DNA circulating in the blood, is emerging as a practical alternative. In the context of ICC, researchers are exploring liquid biopsy for several purposes: determining the tumor’s molecular profile to guide targeted therapy, detecting leftover cancer cells after surgery (minimal residual disease), monitoring for recurrence, and screening high-risk populations for early detection.²⁹

One particularly valuable application is tracking resistance to targeted drugs. Patients with FGFR2 fusion-positive ICC who respond to FGFR inhibitors often eventually develop resistance, frequently through new mutations in the FGFR2 gene itself. Studies have used liquid biopsy to detect these resistance mutations in circulating tumor DNA, sometimes before the cancer visibly progresses on imaging. This information can guide decisions about switching therapies or sequencing different FGFR inhibitors strategically.³⁰

Living With Biliary Obstruction

Many ICC patients, whether their cancer is operable or not, experience blockage of bile ducts at some point. This causes jaundice, intense itching, and a cascade of metabolic problems. Biliary drainage, using a stent or external tube to bypass the blockage, can dramatically lower bilirubin levels and relieve itching. One prospective study found that successful drainage was associated with improvements in social function and mental health.³¹

However, the picture is complicated. A more recent study found that while drainage achieved a steep drop in bilirubin and relieved itching, overall quality-of-life scores actually declined over the following weeks, with social well-being taking a particular hit and emotional improvements fading by four weeks.³² The takeaway is not that drainage should be avoided, since it is medically necessary in most cases, but that relieving the physical problem does not automatically resolve the psychological and social burden. Patients dealing with biliary stents or drainage tubes benefit from comprehensive support that includes nutritional counseling, psychological care, and palliative services alongside the procedural intervention.

How Geographic Patterns Shape Risk

ICC’s geographic distribution is uneven in ways that reflect the underlying causes in each region. The highest rates globally are in parts of Thailand and other Southeast Asian countries where liver fluke infection is endemic. The fluke itself causes direct mechanical damage to bile duct cells, and its secreted proteins trigger inflammatory and immune responses that compound the injury over time. Exposure to environmental carcinogens alongside the parasitic infection further amplifies risk.³³

Within the United States, studies have found that the incidence patterns of ICC and extrahepatic cholangiocarcinoma are more similar to each other than either is to hepatocellular carcinoma, with overlapping racial distributions and peak age ranges.³⁴ This makes sense given that both types of cholangiocarcinoma arise from bile duct cells and share many risk factors, while hepatocellular carcinoma follows a more distinct set of drivers. For patients and clinicians, the practical implication is that ICC surveillance strategies may need to account for regional risk profiles rather than applying a one-size-fits-all approach, particularly in populations with high rates of hepatitis, liver fluke exposure, or primary sclerosing cholangitis.