Fibrolamellar Carcinoma: A Young Adult Liver Cancer

Fibrolamellar hepatocellular carcinoma (FLC) is a rare and distinct variant of liver cancer that primarily affects adolescents and young adults without underlying liver disease. Unlike the more common hepatocellular carcinoma (HCC) that typically arises in cirrhotic livers, fibrolamellar carcinoma develops in otherwise healthy livers, making it a unique entity in hepatobiliary oncology. This article provides a comprehensive overview of FLC, including its pathophysiology, clinical presentation, radiological features, and management strategies, with a focus on the key symptoms and diagnostic challenges associated with this rare malignancy.

Epidemiology and Pathophysiology of Fibrolamellar Carcinoma

Fibrolamellar carcinoma accounts for less than 1% of all primary liver cancers, yet it is the most common liver cancer in young adults aged 15-35 years. It shows no gender predilection and has a higher incidence in Caucasian populations. Unlike typical HCC, which is strongly associated with hepatitis B/C infection, alcohol use, or metabolic liver disease, FLC occurs in patients with no known risk factors. The pathogenesis involves a unique DNAJB1-PRKACA fusion gene, resulting from a deletion on chromosome 19, which leads to constitutive activation of protein kinase A. This molecular hallmark is present in nearly all cases and is a key diagnostic biomarker.

Fibrolamellar Carcinoma Symptoms and Clinical Presentation

The most common FLC symptoms include vague abdominal pain, a palpable right upper quadrant mass, nausea, weight loss, and fatigue. Because these symptoms are nonspecific and the tumor grows slowly, diagnosis is often delayed for months. Unlike typical HCC, jaundice and ascites are uncommon unless the tumor is very large or obstructs the biliary tract. Approximately 20-30% of patients are asymptomatic at diagnosis, with the tumor found incidentally during imaging for unrelated reasons. Laboratory studies may show elevated serum levels of vitamin B12-binding protein and neurotensin, which can serve as tumor markers. Alpha-fetoprotein (AFP) is usually normal or only mildly elevated, contrasting with typical HCC.

Given the rarity of FLC, awareness among clinicians is crucial. Young adults presenting with unexplained upper abdominal symptoms or a liver mass should raise suspicion for this entity. Early recognition of its symptoms can lead to timely surgical intervention, which offers the best chance for cure.

Fibrolamellar Hepatocellular Carcinoma Radiology

Imaging plays a pivotal role in the radiologic diagnosis of FLC. On ultrasound, the tumor typically appears as a well-defined, lobulated, hypoechoic or hyperechoic mass with a central scar. Contrast-enhanced computed tomography (CT) reveals a large, heterogeneous mass with a central scar that shows delayed enhancement. The scar is often calcified in 50-70% of cases, a feature that helps distinguish fibrolamellar carcinoma from focal nodular hyperplasia (FNH) or typical HCC. On magnetic resonance imaging (MRI), the tumor is hypointense on T1-weighted images and hyperintense on T2-weighted images, with the central scar showing low T2 signal intensity due to fibrous tissue. The calcified scar is best seen on CT and is a hallmark of this tumor.

Other radiological features include the absence of cirrhosis, the presence of lymph node metastases at diagnosis in up to 50% of patients, and occasional vascular invasion. The differential diagnosis on imaging includes FNH, hepatic adenoma, and metastatic disease. However, the combination of a large liver mass with a calcified central scar in a young noncirrhotic patient is highly suggestive of FLC. Nuclear medicine studies, such as FDG-PET, may show increased uptake and can help detect extrahepatic metastases.

Diagnosis and Staging

Definitive diagnosis requires histopathologic examination of tumor tissue. Core needle biopsy or surgical resection specimens show large polygonal tumor cells with abundant eosinophilic cytoplasm, prominent nucleoli, and lamellar fibrosis interspersed between nests of tumor cells. Immunohistochemically, tumor cells are positive for CK7, CK19, and epithelial membrane antigen (EMA), while negative for AFP and HepPar1. The presence of the DNAJB1-PRKACA fusion gene can be confirmed by reverse transcription-polymerase chain reaction (RT-PCR) or fluorescence in situ hybridization (FISH). Staging follows the same TNM system as HCC, but prognosis is more favorable for resectable disease due to the absence of underlying liver disease.

Treatment Options for Fibrolamellar Carcinoma

Surgical resection is the mainstay of treatment for localized FLC. Complete removal of the tumor with negative margins offers the best long-term survival, with 5-year survival rates of 70-80% for resectable cases. For patients with unresectable disease due to extensive intrahepatic involvement or metastases, liver transplantation has been performed in selected cases, but recurrence rates are high. Systemic therapies, including chemotherapy (e.g., platinum-based regimens) and targeted agents, have limited efficacy. Recent clinical trials are exploring the use of protein kinase A inhibitors, given the molecular target provided by the fusion gene. For advanced disease, locoregional therapies such as transarterial chemoembolization (TACE) or radiofrequency ablation can be used for palliation. The role of immunotherapy is still under investigation.

Given the rarity of FLC, treatment should ideally be offered at specialized centers with multidisciplinary expertise. Clinical trials are available for patients with advanced disease and should be considered. Regular surveillance with imaging and tumor markers is recommended after treatment due to the risk of late recurrence.

Prognosis and Long-Term Outcomes

The prognosis of FLC is generally better than that of typical HCC, but it remains a serious malignancy. Five-year survival for all stages combined is approximately 40-50%. Factors associated with worse outcomes include larger tumor size, lymph node involvement, vascular invasion, and inability to achieve complete resection. Late recurrences beyond 5 years are not uncommon, emphasizing the need for prolonged follow-up. Young patients with resectable disease have the most favorable prognosis, and with advances in molecular targeted therapies, outcomes may improve in the future.

• Fibrolamellar carcinoma is a rare liver cancer in young adults without cirrhosis.
• Fibrolamellar hepatocellular carcinoma radiology often shows a calcified central scar.
• Fibrolamellar carcinoma symptoms include abdominal pain and a mass, but are nonspecific.
• Diagnosis relies on histology and molecular testing for the DNAJB1-PRKACA fusion.

In summary, fibrolamellar carcinoma is a distinct liver cancer that demands a high index of suspicion in young adults. Recognizing the typical radiological findings and characteristic symptoms can expedite diagnosis and improve outcomes. Ongoing research into the molecular mechanisms of this disease holds promise for novel targeted therapies.