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Liver and intrahepatic bile ducts - Tumor

Benign tumors

Angiomyolipoma (AML)

Reviewers: Deepali Jain, M.D. (see Reviewers page)
Revised: 9 January 2013, last major update February 2012
Copyright: (c) 2004-2013, PathologyOutlines.com, Inc.


● Mesenchymal tumor arising from perivascular epithelioid cells (PEC)
● Smooth muscle HMB45+ is defining and consistent feature; similar histologically to renal angiomyolipoma but no proven association
● Myoid and vascular components are clonal; adipose tissue component may be reactive
● Other lesions derived from PEC (PEComas) include lymphangioleiomyoma, clear cell (sugar) tumor of lung and rare myomelanocytic tumors
● Approximately 200 cases reported through 2004
● Often misdiagnosed as lipoma, hepatocellular adenoma or carcinoma, sarcoma, other metastatic neoplasms (Am J Surg Pathol 1999;23:34 (review))

Clinical features

● Liver is #2 site for AML after kidney
● Mean age 50 years, range 9-79 years; 80% women
● Only 6-10% associated with tuberous sclerosis, these cases are associated with renal AML and may be multiple
● Similar gene expression profile as hepatic stellate cells and stem cells (Hum Pathol 2005;36:341, Mol Med 2007;13:160)

Radiologic images

Multiple hypointense lesions

Case reports

● 46 year old woman with 15+ tumors but without tuberous sclerosis (Mod Pathol 2002;15:167)
● 50 year old man (Hepatobiliary Pancreat Dis Int 2005;4:152)

Gross description

● Well-circumscribed but not encapsulated, typically solitary masses up to 20 cm (1-36 cm), yellow-gray-white
● Necrosis present in larger tumors, may contain hemorrhage, background liver is normal

Gross images

Large lobulated tumor with areas containing fat

Multiple lesions

Case report: 50 year old man

Micro description

● Mature adipose tissue, smooth muscle cells and thick walled blood vessels with loss of elastic lamina
● Spindle cells radiate from walls
● Extramedullary hematopoiesis in 40%; represents hematopoietic function of liver
● Smooth muscle cells are epithelioid or spindled with clear (spider web appearance) or eosinophilic cytoplasm or pleomorphic
● Mast cells common
● Occasional features are cellularity, nuclear pleomorphism with intranuclear inclusions, tumor giant cells
● No/rare mitotic figures
● Most cases have mixed patterns; unusual patterns are angiomatous, inflammatory, lipomatous (70%+ fat), myomatous, oncocytic, pelioid, trabecular
● Inflammatory subtype resembles inflammatory myofibroblastic tumor or follicular dendritic cell tumor (Ann Diagn Pathol 2010;14:240); trabecular variant mimics hepatocellular carcinoma
● Malignant cases recur / metastasize; definite criteria for malignancy not established; features associated with malignancy are: large size (10 cm+), increased mitoses (2-5/hpf), coagulative necrosis, vascular invasion, CD117 weak/negative (Am J Surg Pathol 2008;32:793)

Micro images


Smooth muscle, vessels, adipose

H&E and stains

Case report: 50 year old man - H&E and HMB45

Positive stains

● Smooth muscle cells: strong - HMB45, MelanA/MART1, microphthalmia transcription factor (50%) and other melanin markers (Arch Pathol Lab Med 2002;126:49), including HBSA5, MART-1, HMB-50, CD63 (NKIC3)
● Variably positive for smooth muscle actin and desmin; S100 (adipose cells); c-kit/CD117 (all cell types, Am J Surg Pathol 2002;26:493 (c-kit staining))

Negative stains

● Cytokeratin, HepPar1

Electron microscopy description

● Epithelioid myoid cells have premelanosomes, numerous mitochondria, abundant rough endoplasmic reticulum, glycogen, tight junctions and basal lamina, but no thick filaments

End of Liver and intrahepatic bile ducts-Tumor > Benign tumors > Angiomyolipoma (AML)

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