The Diagnostic Odyssey of Uncommon Liver Lesions

Introduction

Hepatic tumors offer quite a difficulty in getting an informed diagnosis possible. This holds true for both common and uncommon hepatic lesions. Some examples of common hepatic lesions include hepatocellular carcinoma (HCC), cholangiocarcinoma, and liver metastasis. The imaging findings for each of these lesions differ greatly from one another and have sufficient backed-up data in the literature to use for reference. However, the uncommon hepatic lesions barely make the cut and carry little to no data to confirm their diagnosis. Hence, it is evident for a radiologist to identify these imaging abnormalities and deliver an appropriate conclusion in favor of the patient. This article aims to discuss some uncommon liver lesions in brief and provide insights related to diagnostic affairs.

What Are Liver Lesions?

Liver lesions refer to abnormal growths that may either be benign or malignant. Benign lesions are usually not a subject of concern, as they often tend to resolve without seeking any specific treatment. Cancerous lesions, however, need medical attention to prevent them from incurring any serious damage. The examples of each type are listed below.

1. Benign Liver Lesions: Liver hemangioma, focal nodular hyperplasia, liver adenoma, and cystic lesions.

2. Malignant Liver Lesions: Hepatocellular carcinoma, cholangiocarcinoma, and metastatic liver cancer.

A third category, referred to as uncommon liver lesions, include:

1. Lymphoma (cancer of white blood cells).

2. Combined hepatocellular and cholangiocarcinoma (cancer of liver and bile ducts).

3. Angiosarcoma (caner in lining of blood vessels).

4. Inflammatory pseudotumor (a non cancerous growth that mimics cancerous growth).

5. Hepatoblastoma ( a form of liver cancer).

6. Hydatid cyst (cyst caused by echinococcus tapeworm species, occurring mainly in liver).

The symptoms presented by the lesions usually depend on their type. Benign lesions are known to present with no symptoms at all, except when they have outgrown in size, causing them to press up against surrounding organs. Abdominal discomfort is a common finding in such cases. Cancerous lesions present with no symptoms in their early stages but, over time, may result in abdominal pain, fatigue, loss of appetite, the feeling of satiety, the abnormal lump felt toward the top right side of the stomach, and yellowing of the skin or eye-whites indicating jaundice. The rest of the article dives deeper into the individual characteristics of the uncommon hepatic lesions.

What Are the Imaging Characteristics of Uncommon Liver Lesions?

1. Lymphoma

Hepatic lymphoma can be classified as either primary or secondary lymphoma. The latter is a more common entity, the non-Hodgkin’s lymphoma being the most frequent type.

• Ultrasonography

The common imaging findings observed on ultrasonography include multiple focal liver lesions, hepatomegaly (enlargement of the liver), splenomegaly (enlargement of the spleen), and lymphadenopathies. Primary hepatic lymphoma usually presents as a solitary mass, whereas secondary hepatic lymphoma tends to be multifocal in appearance.

• Computed Tomography (CT)

The lymphoma is presented as a relatively less enhanced lesion on CT. Lymphadenopathy may be present, with the masses or nodules showing evident signs of hemorrhage or necrosis.

• Magnetic Resonance Imaging (MRI)

T1 hypo intensity and T2 hyperintensity are typical imaging findings of lymphoma on an MRI. Peripheral rim enhancement of the lesion may be present.

2. Combined Hepatocellular (HCC) and Cholangiocarcinoma (CC)

This particular lesion is an extremely rare entity that is categorized into three subtypes based on its clinical presentation. Type 1 is where both the HCC and CC parts of the tumor are distinct and grow separately. Type 2 refers to a combined tumor where both parts are contiguous with each other but yet grow independently. Type 3 is the mixed type, and it is impossible to distinguish the two components from one another.

• Computed Tomography (CT)

Arterial enhancement and capsular retraction are the usual findings on a CT. The bile duct may or may not be dilated.

• Magnetic Resonance Imaging (MRI)

The imaging findings resemble that of a CT. The lesion presents itself as a T2 hyperintense mass, with intertumoral lipid observed in some cases.

3. Angiosarcoma

Regarded as one of the most common mesenchymal tumors of the liver, angiosarcoma accounts for about 2 percent of all primary hepatic tumors. They are most commonly sighted on the breast or the skin. Exposure to environmental toxins and radiation is thought to be the primary cause of its incidence. The symptoms are too vague to make an informed diagnosis, and hence, the prognosis tends to be poor in the majority of cases.

• Ultrasonography

The lesion may be multifocal or solitary in appearance. A hemorrhagic mass can be observed.

• CT

Arterial enhancement is more clearly depicted on a CT. A hypodense exterior with a necrotic interior is a common observation on a pre-contrast CT scan.

• MRI

T2 weighted images may show hypointense internal areas on an MRI scan.

4. Inflammatory Pseudotumor (IPT)

This tumor marks a close resemblance to the inflammatory myofibroblastic tumor and comprises varying levels of inflammatory cells. The prognosis of IPTs is proven to be quite a good post-surgical resection of the tumor.

• Ultrasonography

Well-circumscribed, heterogeneous lesions accompanied by calcifications are a typical finding on an ultrasound. No significant enhancements are reported.

• CT

Rim-like portal venous enhancement of the tumor is observed in CT imaging.

• MRI

Hypointense T1 weighted images and hyperintense T2 weighted images are typical findings.

5. Hepatoblastoma

This is the most commonly encountered primary hepatic lesion in children below 2 years of age. It is extremely rare to find hepatoblastoma in adults. Clinically, jaundice and abdominal stiffness are the most common findings observed. This tumor is classified into three distinct types, namely epithelial, mixed epithelial, and mesenchymal. The epithelial type may present as a homogeneous entity, while the mixed type appears heterogeneous owing to the presence of osteoid, cartilaginous, and fibrous components. Arterial enhancement is observed on both CT and MRI.

6. Hydatid Cyst

The Echinococcus tapeworms are responsible for the incidence of hydatid cysts. Contaminated food is the typical means to get infected. The imaging findings typically include unilocular or multilocular appearance, with or without calcifications near the periphery.

Conclusion

The rarity of these lesions accounts for their negligible mention in the scientific literature. However, they do occur in some unfortunate cases. Hence, radiologists are expected to be aware of the typical diagnostic findings of such lesions. If the imaging features are not enough, a biopsy of the concerned lesion is the next approach toward making a confirmed diagnosis.