28 April 2010 – Case of the Week #177


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Case of the Week #177


Clinical History


A 25 year old Philipino man presented with chronic abdominal pain, gradual loss of appetite and weight loss, with no change in bowel habits. 


Ultrasound revealed a large soft tissue mass filling the epigastric, umbilical and bilateral lumber regions.  It filled most of the peritoneal cavity and extended deeply into the para-aortic region. It displaced both kidneys laterally, with no lymphadenopathy.


The mass was excised.  Grossly, it was fatty, 25 cm in diameter, and surrounded by small intestine. Cut section revealed that the mass was attached to the wall of the ileum.


Clinical images:


Gross images:



Micro images:



What is your diagnosis?




























Angiomyolipoma of ileum




Microscopically, there were dilated vascular spaces with adipose tissue and foamy histiocytes.  There was intermixed adipose tissue, blood vessels, and smooth muscle bundles.  No atypia was present.


Angiomyolipoma is a benign triphasic tumor composed of dysmorphic, thick walled blood vessels, smooth muscle that appears to spin off from vessel walls, and mature lipid-distended cells.  Tumors occasionally have bizarre epithelioid smooth muscle cells (Int J Surg Pathol 2000;8:67) and possible multinucleation.


Angiomyolipoma is a member of the PEComa family, a concept first proposed by Bonetti (Am J Surg Pathol 1992;16:307), which comprises mesenchymal tumors with perivascular clear cells and epithelioid features that coexpress melanocytic and muscle markers.  It is occasionally associated with tuberous sclerosis (OMIM #191100).  Gastrointestinal angiomyolipoma is very rare.  It usually arises in the kidney (eMedicine), or occasionally in the liver (Arch Pathol Lab Med 2008;132:1679).


The first documented case of symptomatic ileal angiomyolipoma was in a 60 year old woman suffering from intermittent periumbilical pain.  Physical examination revealed a slightly painful abdominal mass.  Segmental resection of the ileum showed a 4 x 4 cm mass with a yellow cut section without hemorrhage or necrosis (Korean J Gastroenterol 2000;36:250).


The second case of ileal angiomyolipoma occurred in a 48 year old woman with vague abdominal pain and bloody stool.  Small bowel intussusception was shown by abdominal CT scan (J Gastroenterol 2005;40:200).


Typically, angiomyolipoma stains positively for HMB45 and MelanA / A103, SMA, calponin, CD117, and S100 (Am J Surg Pathol 2002;26:493).  Theses tumors are negative for keratin.


The differential diagnosis is theoretically broad, encompassing smooth muscle and lipogenic tumors, but narrowed when one carefully identifies the components of the tumor.  Few other tumors are immunoreactive for both smooth muscle and melanocytic markers.  Leiomyomas and leiomyosarcomas have a prominent smooth muscle component, but lack a prominent vascular or adipose component.  Melanomas have prominent atypia, necrosis and infiltrative borders.


Angiomyolipoma typically has benign behavior at other sites, but may occasionally be invasive and have metastases (Am J Surg Pathol 1991;15:1083).


Additional references: PathologyOutlines.com – Kidney Tumor-Adult Benign, World J Gastroenterol 2009;15:1398



Nat Pernick, M.D., President,

and Kara Hamilton, M.S., Associate Medical Editor

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