Tumor-Like Conditions of the Liver

Classification Overview

1. Cavernous Hemangioma

• Composed of multiple large vascular channels of varying sizes, lined by a single layer of flat endothelium, supported by fibrous septa
• Usually solitary; multiple in ~10% of cases
• Reddish-purple or bluish masses, well-circumscribed but rarely encapsulated
• Larger lesions (>5 cm) are called "giant cavernous hemangiomas" and can reach 27 cm

• The vast majority are small and asymptomatic, found incidentally on imaging
• Giant hemangiomas may cause upper abdominal pain (from partial infarction or pressure on adjacent structures), nausea, early satiety
• Kasabach-Merritt syndrome: thrombocytopenia due to platelet sequestration - seen in infants, rare in adults
• Malignant transformation has NOT been reported

• Ultrasound: echogenic, uniform mass in posterior right lobe, typically <3 cm
• CT (contrast): peripheral nodular enhancement progressing centripetally ("fill-in pattern") - pathognomonic
• MRI: hypointense on T1, strikingly hyperintense on T2; gadolinium shows peripheral nodular enhancement

Caution: Percutaneous biopsy should NOT be performed if hemangioma is suspected due to risk of severe hemorrhage.

• Sleisenger and Fordtran's Gastrointestinal and Liver Disease, p. 1864-1865
• Bailey and Love's Short Practice of Surgery, p. 1234

2. Focal Nodular Hyperplasia (FNH)

• Well-demarcated, poorly encapsulated nodule, often several centimeters in diameter
• Characteristic central stellate (star-shaped) scar with fibrous septa radiating to the periphery (see image below)

FIG - Focal Nodular Hyperplasia: (A) Resected specimen with lobulated contours and central stellate scar. (B) Histology showing broad fibrous scar with mixed hepatic arterial and bile duct elements within hepatic parenchyma. (Robbins & Kumar Basic Pathology)

• Contains both hepatocytes AND Kupffer cells
• Central scar contains large abnormal vessels and ductular reactions along the spokes
• Lacks normal portal areas and terminal hepatic veins
• No capsule

• Hypervascular on arterial phase CT, isodense to liver on venous phase, with visible central scar
• MRI (liver-specific agents like gadoxetate): FNH takes up contrast in the hepatobiliary phase, distinguishing it from adenoma and metastases

• No malignant potential
• Does NOT typically rupture spontaneously
• No association with underlying liver disease
• Mild association with oral contraceptives (weaker than adenoma)

• Robbins & Kumar Basic Pathology, p. 625
• Schwartz's Principles of Surgery, p. 1402

3. Hepatocellular Adenoma

• Predominantly reproductive-age women (typically >30 years)
• Historically linked to oral contraceptive (OCP) use; with lower-dose estrogen formulations, the major risk factor has shifted to obesity and metabolic syndrome
• Driver mutations described include gain-of-function mutations in β-catenin (associated with malignant transformation risk)

• Soft, encapsulated, tan to light brown
• Usually solitary (multiple = hepatic adenomatosis)

• Sheets of normal-appearing to atypical hepatocytes
• No portal tracts, no bile ducts, no Kupffer cells
• Prominent thick-walled arteries at the periphery
• No true lobular architecture

FIG - Hepatic Adenoma: (A) Gross specimen. (B) Histology - cords of hepatocytes, arterial supply (arrow), no portal tracts. (Robbins & Kumar Basic Pathology)

• Rupture with intraperitoneal hemorrhage: occurs in 10-25% of cases, can be life-threatening
• Malignant transformation to HCC: up to 10% risk, especially with β-catenin mutations and in men
• Risk of both complications increases with lesion size (>4-5 cm)
• Documented high maternal and fetal mortality if rupture occurs during pregnancy

• CT: sharply defined borders, hypervascular on arterial phase, hypo- or isodense on venous phase
• MRI: hyperintense on T1 (fat/glycogen content), early enhancement with gadolinium
• Liver-specific MRI agents (gadoxetate/Eovist): adenoma does NOT enhance in hepatobiliary phase (distinguishes from FNH)

• Discontinue OCP/estrogen
• Surgical resection recommended for lesions >4-5 cm due to rupture and malignancy risk
• Smaller lesions may regress after stopping OCP
• Robbins & Kumar Basic Pathology, p. 626
• Schwartz's Principles of Surgery, p. 1403

4. Hepatic Cysts

• Most common liver lesion overall; prevalence 5-14% of population, higher in women
• Thin-walled, contain serous fluid; no communication with biliary tree
• Usually asymptomatic; incidental finding on imaging
• No malignant potential; resection only if symptomatic

• Autosomal dominant; associated with polycystic kidney disease
• Can cause severe symptoms from mass effect
• Severe cases: hepatic resection or liver transplantation

• Congenital ductal plate malformation causing segmental cystic dilatation of intrahepatic biliary radicals
• Associated with biliary lithiasis, cholangitis, biliary abscess
• ~7% develop cholangiocarcinoma
• Diagnosed by MRCP/ERCP; treatment is biliary drainage

• Parasitic infection; can form large cystic masses mimicking tumors
• "Daughter cysts" on imaging are characteristic
• Schwartz's Principles of Surgery, p. 1402-1403

5. Bile Duct Hamartoma (Von Meyenburg Complexes)

• Small lesions (2-4 mm), typically visualized on liver surface at laparotomy
• Firm, smooth, whitish-yellow in appearance
• Can be extremely difficult to differentiate from small metastatic deposits - excisional biopsy often required

Key Differentiating Features at a Glance

Recent Literature Note