Liver & intrahepatic bile ducts

• ICD-O: 9120/0 - hemangioma, NOS
• ICD-11: 2E81.2Y - other specified benign vascular neoplasms of infancy and childhood

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Contributed by Xuchen Zhang, M.D., Ph.D.

Contributed by Xuchen Zhang, M.D., Ph.D. and Deepali Jain, M.D.

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• Hepatic angiosarcoma:
  • Solid spindle areas with marked atypia
  • Ki67 proliferation index > 10% (Pediatr Blood Cancer 2017;64:e26627)
  • Irregular margins infiltrating into adjacent liver parenchyma
  • Variable GLUT1 immunopositivity
• Mesenchymal hamartoma:
  • Hypocellular fibromyxoid stroma with bland spindle cells
  • Malformed bile duct in duct plate configuration
  • Occasionally can have prominent vascular proliferation
  • GLUT1 negative
• Cavernous hemangioma:
  • Usually well circumscribed
  • Variably sized, dilated and thin walled vessels lined by a single layer of flat endothelial cells
  • No cytologic atypia or mitosis
  • GLUT1 negative
• Hepatic small vessel neoplasm:
  • Average patient age 54 years, more common in men (Hum Pathol 2016;54:143)
  • Infiltration into adjacent liver parenchyma
  • Anastomosing, closely packed vascular spaces lined by flat endothelial cells with occasional hobnailing
  • GLUT1 negative
  • Recurrent hotspot mutations of GNAQ, GNA11, GNA14 and PIK3CA
• Hepatic vascular malformation (HVM):
  • Rare cause of liver mass lesions
  • Thicker walled shunt vessels lead to a central area of vascular proliferation, congestion, large dilated blood filled spaces with areas of organizing thrombi, calcification and fibrosis
    • The periphery of the lesion often consists of an irregular rim of loose, sometimes myxoid reactive stroma containing numerous capillary type vessels
  • Unlike in HIH, the demarcation between HVM and normal liver tissue is indistinct (Hum Pathol 2004;35:200)
  • The adjacent liver tissue often contains abnormally enlarged, dilated vessels in the portal area and dilated hepatic sinusoids (Hum Pathol 2004;35:200)
  • GLUT1 either negative or with focal staining but lacks the strong and diffuse staining as seen in HIH (Hum Pathol 2004;35:200)

• N Engl J Med 2021;385:e10, Lancet 2017;390:85

A 5.5 x 3.5 cm lesion in the liver (first image) is identified in the autopsy of a 10 month old girl. External examination reveals multiple cutaneous hemangiomas on the trunk and upper extremities. Microscopic examination of the liver lesion reveals a vascular neoplasm composed of numerous small and capillary-like vascular channels lined by plump endothelial cells with no cytologic atypia in the periphery region (second image). The tumor exhibits an irregular interface with the adjacent liver parenchyma. In the central region of the tumor, there are a few large, cavernous vessels lined by flattened endothelial cells, accompanied by fibrosis of the surrounding stroma (third image). The tumor cells are positive for CD31, CD34 and GLUT1 by immunohistochemistry. Which is the best diagnosis of this lesion?

1. Angiosarcoma
2. Cavernous hemangioma
3. Hepatic infantile hemangioma
4. Mesenchymal hamartoma

C. Hepatic infantile hemangioma. The gross photograph and microscopic description identify the lesion as a benign vascular neoplasm. Micrograph shows a vascular neoplasm with numerous small and capillary-like vascular channels lined by plump endothelial cells with no cytologic atypia. In the center of the lesion shows stromal fibrosis and few large, cavernous vessels lined by flattened endothelial cells. CD31, CD34 and GLUT1 are positive in the lesional endothelial cells, confirming diagnosis of hepatic infantile hemangioma. Answer A is incorrect because angiosarcoma should show marked nuclear atypia, abundant atypical mitotic figures and solid spindled areas. Answer B is incorrect because cavernous hemangioma is a common subtype of hepatic hemangioma in adults showing circumscribed proliferation of variably sized, dilated and thin walled vessels lined by a single layer of flat endothelial cells. Answer D is incorrect because mesenchymal hamartoma, the second most common benign pediatric hepatic tumor after hepatic infantile hemangioma, is comprised of variable proportions of disorganized arrangements of primitive mesenchyme with benign dilated or branching bile ducts and clusters of normal appearing hepatocytes.

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Reference: Hepatic infantile hemangioma

Multiple liver lesions (ranging from 0.5 to 3.5 cm) were incidentally identified on ultrasound of a 6 month old girl. A core biopsy was performed, which revealed a vascular neoplasm as illustrated in the micrograph (first image). The tumor cells are positive for CD34 (second image) and GLUT1 (third image) by immunohistochemistry. Which immunohistochemical stain is most characteristic for diagnosing this lesion?

1. CD31
2. CD34
3. GLUT1
4. HepPar1

C. GLUT1. The microscopy shows a benign appearing vascular neoplasm. GLUT1 is strongly and diffusely positive in infantile hemangiomas and helps to exclude nonneoplastic vessels and vascular malformation as well as most of the other benign vascular neoplasms that do not express GLUT1. Answers A and B are incorrect because CD31 and CD34 are vascular markers that will be positive in all neoplastic or nonneoplastic vessels. Answer D is incorrect because HepPar1, a hepatocytic marker, is not helpful in characterizing a vascular lesion.

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Reference: Hepatic infantile hemangioma