Intrahepatic Cholangiocarcinoma: Understanding Your Pathology Report

by Stephanie Reid, MD FRCPC
April 22, 2026

Intrahepatic cholangiocarcinoma is a type of cancer that starts in the small bile ducts located within the liver. Bile ducts are the tubes that carry bile, a fluid that helps digest fats, from the liver to the intestine. Intrahepatic cholangiocarcinoma is distinct from hepatocellular carcinoma, which starts from the liver cells themselves, and from extrahepatic cholangiocarcinoma, which starts in the bile ducts outside the liver. Intrahepatic cholangiocarcinoma is the second most common primary liver cancer after hepatocellular carcinoma and accounts for approximately 10 to 15% of primary liver cancers worldwide. Its incidence has been rising over the past several decades in North America and Europe.

This article will help you understand the findings in your pathology report — what each term means and why it matters for your care.

What causes intrahepatic cholangiocarcinoma?

Intrahepatic cholangiocarcinoma develops when the cells lining the small bile ducts within the liver accumulate genetic damage over time. Known risk factors fall into two broad groups that correspond roughly to the two main subtypes of the disease.

Risk factors shared with hepatocellular carcinoma — most relevant for the small-duct subtype — include:

• Chronic viral hepatitis — Long-standing infection with hepatitis B or hepatitis C.
• Cirrhosis — Long-standing liver scarring from any cause.
• Metabolic liver disease — Fatty liver disease related to obesity, type 2 diabetes, or alcohol use.

Risk factors shared with extrahepatic cholangiocarcinoma — most relevant for the large-duct subtype — include:

• Primary sclerosing cholangitis — A chronic disease that causes scarring and narrowing of the bile ducts.
• Liver fluke infections — Parasitic infections with Opisthorchis viverrini or Clonorchis sinensis, most common in parts of Southeast Asia.
• Bile duct cysts and congenital abnormalities — Structural differences in the bile ducts present from birth.
• Other conditions — Chronic bile duct inflammation or infection, and rare occupational chemical exposures.

Many patients have no identifiable risk factor. The incidence of intrahepatic cholangiocarcinoma varies widely by region; it is particularly common in parts of Southeast Asia and relatively uncommon in Europe and North America, although rates have been rising in Western countries.

What are the symptoms of intrahepatic cholangiocarcinoma?

Early intrahepatic cholangiocarcinoma often causes no symptoms. Because the tumor grows within the liver rather than blocking the main bile ducts, many tumors grow silently until they become relatively large. When symptoms do appear, they are often non-specific and include fatigue, discomfort or pain in the right upper abdomen, loss of appetite, and unintentional weight loss.

Tumors that arise near the larger bile ducts inside the liver can block bile flow and cause jaundice (yellowing of the skin and eyes), itching, dark urine, pale stools, and occasional episodes of bile duct infection (cholangitis). Because symptoms are often absent or mild until the disease is advanced, many intrahepatic cholangiocarcinomas are discovered incidentally on imaging performed for another reason.

Types of intrahepatic cholangiocarcinoma

Pathologists recognize two main types of intrahepatic cholangiocarcinoma based on where the tumor arises within the liver and how it grows. The distinction is important because the two types differ in their risk factors, microscopic appearance, molecular features, and outlook.

• Small-duct type — Arises from the smaller bile ducts in the peripheral parts of the liver and typically forms a distinct mass within the liver tissue. This type is more likely to occur in people with chronic viral hepatitis, cirrhosis, or metabolic liver disease. Under the microscope, it often shows a pattern in which tumor cells gradually replace normal liver cells. Small-duct tumors are more likely to carry IDH1 or IDH2 mutations and FGFR2 fusions, both of which can be targeted with specific drugs. Some specific subtypes, such as cholangiolocarcinoma, belong in this category. Small-duct tumors generally have a better outlook than large-duct tumors.
• Large-duct type — Arises from the larger bile ducts closer to the hilum of the liver (the area where major ducts and vessels enter and leave the liver). This type tends to grow along the bile ducts and spread into the surrounding liver tissue. It shares risk factors with extrahepatic cholangiocarcinoma, including primary sclerosing cholangitis and liver fluke infections. Under the microscope, it closely resembles extrahepatic cholangiocarcinoma and often produces mucus. Large-duct tumors are more likely to carry KRAS, TP53, and SMAD4 alterations and have a worse outlook than small-duct tumors.

How is the diagnosis made?

The diagnosis of intrahepatic cholangiocarcinoma is usually made using a combination of imaging, a tissue sample examined under the microscope by a pathologist, and — in many cases — molecular testing. Imaging studies such as ultrasound, CT, MRI, and PET scans are used to locate the tumor, measure its size, and assess spread. Small-duct tumors usually appear as a mass in the liver, while large-duct tumors may show bile duct thickening and narrowing with dilation of the ducts upstream. Because the tumor can look similar to hepatocellular carcinoma or to cancers that have spread to the liver from another site, imaging features alone are rarely enough to establish the diagnosis.

Tissue is usually obtained by a needle biopsy through the skin under ultrasound or CT guidance. In selected cases, cells may be sampled by fine-needle aspiration or bile duct brushings during endoscopic retrograde cholangiopancreatography (ERCP). When the cancer is removed surgically, the full resection specimen is also examined.

Under the microscope, intrahepatic cholangiocarcinoma is almost always an adenocarcinoma, meaning it forms abnormal gland-like structures. The glands can be round, tubular, or cord-like and are often surrounded by dense scar-like tissue called desmoplastic stroma. The tumor cells frequently invade nearby portal tracts, and can grow along nerves and into small blood vessels and lymphatic channels. Mucus production is common in large-duct tumors but usually absent in small-duct tumors. Because intrahepatic cholangiocarcinoma can closely resemble other cancers on biopsy, the pathologist often uses special stains called immunohistochemistry to confirm the diagnosis and rule out hepatocellular carcinoma or adenocarcinomas from other sites such as the pancreas, colon, stomach, or breast. Pathologists also look for precancerous changes in nearby bile ducts, including biliary intraepithelial neoplasia, which supports the idea that the cancer developed gradually over time.

Histologic grade

Histologic grade describes how closely the tumor cells resemble normal bile duct cells under the microscope and is based mainly on how much of the tumor forms well-organized glands. Grade helps predict how the cancer is likely to behave and is one of several factors used to guide treatment.

• Well differentiated — The tumor forms mostly well-organized glands that resemble normal bile ducts. These tumors tend to grow more slowly and are generally less aggressive.
• Moderately differentiated — The tumor shows a mix of gland-forming and less organized areas. This is the most common grade.
• Poorly differentiated — Few glands are formed and the tumor cells look very abnormal. These tumors behave more aggressively and are more likely to spread.

Lymphovascular (vascular) invasion

Lymphovascular invasion, often called vascular invasion in intrahepatic cholangiocarcinoma, means that tumor cells are found inside blood vessels or lymphatic channels within or near the tumor. In intrahepatic cholangiocarcinoma, vascular invasion is particularly important because the tumor spreads preferentially through blood vessels to other parts of the liver and, later, to more distant organs.

• Microvascular invasion — Tumor cells are seen inside small blood vessels under the microscope. This finding raises the pathologic tumor stage from pT1 to pT2 when a single tumor is present, and is associated with a higher risk of recurrence after surgery.
• Macrovascular invasion — The tumor has grown into a larger blood vessel such as a branch of the portal vein or a hepatic vein, usually visible on imaging. Macrovascular invasion generally excludes surgical resection as a curative option.

Lymphatic invasion — tumor cells inside small lymphatic channels — does not directly change the pathologic tumor stage but increases the risk of spread to regional lymph nodes.

Perineural invasion

Perineural invasion means that cancer cells are found growing around or along nerves. Nerves can act as pathways that allow tumor cells to spread beyond the visible edge of the tumor. Perineural invasion is more common in the large-duct subtype of intrahepatic cholangiocarcinoma, where the tumor grows along the bile ducts, and is associated with a higher risk of local spread and recurrence.

Surgical margins

A margin is the cut edge of tissue removed during surgery. For intrahepatic cholangiocarcinoma, the pathologist examines two main margins: the liver tissue margin (the cut edge of the liver parenchyma) and, when a portion of a bile duct has also been removed, the bile duct margin.

• Negative margin — No cancer cells are seen at the cut edge. This suggests that the tumor was completely removed and is associated with the best chance of long-term survival.
• Close margin — Tumor cells are within a few millimeters of the cut edge but do not reach it. The clinical meaning of a close margin varies, and your surgeon will consider it alongside other features of the tumor.
• Positive margin — Tumor cells are present at the cut edge. A positive margin raises the risk of recurrence in the remaining liver and may prompt consideration of further treatment.

Lymph nodes

Lymph nodes are small immune organs scattered throughout the body. Spread to regional lymph nodes — those located near the liver and along the main bile ducts — is an important prognostic feature of intrahepatic cholangiocarcinoma and is associated with a substantially worse outcome. During surgery, the surgeon removes regional lymph nodes for examination under the microscope. The pathology report will state the total number of lymph nodes examined and the number containing cancer. Current guidelines recommend examining at least 6 regional lymph nodes to accurately stage the disease.

Biomarker and molecular testing

Biomarker and molecular testing plays a central role in the care of intrahepatic cholangiocarcinoma, particularly for advanced or recurrent disease. Small-duct intrahepatic cholangiocarcinomas in particular carry targetable genetic changes in a high proportion of cases, and current guidelines recommend comprehensive molecular profiling — usually by next-generation sequencing — for anyone with advanced disease. The biomarkers most relevant to intrahepatic cholangiocarcinoma are described below.

IDH1 and IDH2 mutations

IDH1 and IDH2 are enzymes involved in cellular energy production. Mutations in these genes are found in approximately 15-20% of intrahepatic cholangiocarcinomas, almost always in the small-duct type. The mutation is detected by molecular testing on tumor tissue. Tumors with an IDH1 mutation can be treated with the targeted drug ivosidenib, which has been shown to extend progression-free survival in patients with previously treated disease.

FGFR2 fusions

FGFR2 is a gene that helps control cell growth. In some intrahepatic cholangiocarcinomas — almost exclusively the small-duct type — a segment of the FGFR2 gene is fused to another gene, creating an abnormal fusion that drives the cancer. FGFR2 fusions are present in approximately 10-15% of intrahepatic cholangiocarcinomas and are detected by next-generation sequencing. Tumors with an FGFR2 fusion can be treated with FGFR inhibitors, including pemigatinib and futibatinib.

BRAF V600E

BRAF is a gene that, when mutated, drives uncontrolled cell growth. The specific BRAF V600E mutation is uncommon in intrahepatic cholangiocarcinoma (roughly 3 to 5% of cases) but is important because tumors with this mutation can be treated with the combination of dabrafenib and trametinib under a tumor-agnostic approval that applies across cancer types.

NTRK fusions

NTRK fusions are very rare in intrahepatic cholangiocarcinoma, but, when present, make the tumor eligible for highly effective targeted drugs called TRK inhibitors (larotrectinib or entrectinib) under another tumor-agnostic approval.

HER2

HER2 amplification or overexpression is less common in intrahepatic than in extrahepatic cholangiocarcinoma but is occasionally found, particularly in large-duct tumors. When present, HER2-directed therapies such as zanidatamab or trastuzumab-based regimens may be an option.

Mismatch repair (MMR) and microsatellite instability (MSI)

The mismatch repair system is a group of proteins that fix small errors made when cells copy their DNA. When this system does not function, many small mutations accumulate in the tumor, a state called mismatch repair-deficient (dMMR) or microsatellite instability-high (MSI-H). MMR deficiency is uncommon in intrahepatic cholangiocarcinoma, but when present, it makes the tumor eligible for pembrolizumab under a tumor-agnostic approval. A dMMR or MSI-H result may also indicate Lynch syndrome, an inherited condition that increases the risk of several cancers, and should prompt referral for genetic counseling.

Other genetic changes

Molecular testing also often identifies mutations in genes such as KRAS, TP53, ARID1A, and BAP1. These mutations do not currently have approved targeted therapies but may help classify the tumor, provide prognostic information, or identify clinical trial eligibility.

For more information about these and other biomarkers, visit the Biomarkers section.

Pathologic stage (pTNM)

Intrahepatic cholangiocarcinoma is staged using the American Joint Committee on Cancer (AJCC) 8th edition TNM system, which combines information about the tumor (T), regional lymph nodes (N), and distant spread (M). The M category is almost always determined by imaging rather than by pathology. The tumor stage considers the size and number of tumors, the presence of vascular invasion, and whether the tumor has grown through the outer surface of the liver or into adjacent organs.

Tumor stage (pT)

• pTis — Carcinoma in situ. Abnormal cells are confined to the lining of the bile duct and have not invaded deeper tissue.
• pT1a — A single tumor 5 cm or smaller, without vascular invasion.
• pT1b — A single tumor larger than 5 cm, without vascular invasion.
• pT2 — A single tumor of any size with vascular invasion, or multiple tumors (with or without vascular invasion).
• pT3 — Tumor has grown through the outer surface of the liver (the visceral peritoneum).
• pT4 — Tumor directly invades adjacent organs or tissues outside the liver, such as the stomach, small intestine, colon, or diaphragm.

Nodal stage (pN)

• pN0 — No cancer is found in regional lymph nodes.
• pN1 — Cancer is found in one or more regional lymph nodes.

What is the prognosis?

The outlook for intrahepatic cholangiocarcinoma depends mainly on whether the tumor can be completely removed by surgery, the stage at diagnosis, the subtype (small-duct versus large-duct), and the microscopic features of the tumor. Overall, intrahepatic cholangiocarcinoma is an aggressive cancer — in part because many patients are diagnosed after the tumor has grown large or spread — but the availability of effective targeted therapies for the small-duct subtype has improved outcomes meaningfully in recent years.

For patients whose tumors can be completely removed by surgery, five-year survival is approximately 25 to 40%. Survival is substantially lower when the tumor cannot be removed or has already spread; median survival for advanced disease treated with modern chemotherapy plus immunotherapy (gemcitabine, cisplatin, and durvalumab or pembrolizumab) is approximately 12 to 15 months, and longer for patients eligible for targeted therapies.

Pathologic features associated with a worse outcome include:

• Vascular invasion — Especially macrovascular invasion into the portal or hepatic veins, which generally excludes curative surgery.
• Lymph node metastasis — Spread to regional lymph nodes.
• Positive surgical margins — Tumor cells at the cut edge of the liver.
• High histologic grade — Poorly differentiated tumors behave more aggressively.
• Perineural invasion — Tumor growth along nerves.
• Large-duct subtype — Tends to have a worse outlook than the small-duct subtype.
• Multiple tumors — The presence of more than one tumor often reflects spread within the liver.
• Large tumor size — Tumors larger than 5 cm are more likely to recur after surgery.

What happens after the diagnosis?

Care for intrahepatic cholangiocarcinoma is usually coordinated by a multidisciplinary team that includes a hepatobiliary surgeon, a medical oncologist, a radiation oncologist, an interventional radiologist, and a hepatologist. Treatment depends on the size and number of tumors, whether the tumor have invaded blood vessels, whether they have spread to lymph nodes or distant sites, the results of molecular testing, the patient’s overall health, and the rest of the liver.

When the tumor can be removed surgically, a partial liver resection (partial hepatectomy) is the standard approach, sometimes combined with the removal of regional lymph nodes. Liver transplantation is an option in carefully selected patients at specialized centers. After surgery, chemotherapy with capecitabine is often given to reduce the risk of recurrence. When surgery is not possible, locoregional treatments — transarterial chemoembolization (TACE), transarterial radioembolization (TARE), or external-beam radiation — can sometimes control tumor growth. Advanced disease is treated with chemotherapy (gemcitabine and cisplatin) plus immunotherapy (durvalumab or pembrolizumab) as first-line therapy. Patients whose tumors carry an IDH1 mutation, FGFR2 fusion, BRAF V600E mutation, NTRK fusion, HER2 amplification, or MMR deficiency may be eligible for targeted therapies either upfront or after initial treatment.

Treatment of any underlying liver disease — such as antiviral therapy for hepatitis B or C, abstinence from alcohol, or management of metabolic liver disease — continues to be important, because ongoing liver injury increases the risk of new tumors. Follow-up after treatment typically includes regular imaging and blood tests, including the tumor marker CA 19-9.

Questions to ask your doctor

• Is my tumor the small-duct type or the large-duct type?
• What is the size and number of tumors in my liver?
• What is the histologic grade of my tumor?
• Is microvascular or macrovascular invasion present in my pathology report?
• Is perineural invasion present?
• What is the pathologic stage (pTNM) of my cancer?
• If I had surgery, were the surgical margins negative, close, or positive?
• How many lymph nodes were examined, and how many contained cancer?
• Has my tumor been tested for IDH1, FGFR2, BRAF, NTRK, HER2, and mismatch repair status?
• Are any of my molecular test results actionable with a targeted treatment?
• Am I a candidate for surgical resection, liver transplantation, or locoregional therapy?
• Will I need chemotherapy, immunotherapy, or targeted therapy after surgery?
• Am I a candidate for a clinical trial?
• Do I have an underlying liver condition (such as hepatitis, cirrhosis, or primary sclerosing cholangitis) that needs to be managed at the same time?
• What is the plan for follow-up imaging and CA 19-9 testing?