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Soft Tissue Tumors

Myolipoma

 

Author: Nat Pernick, M.D., PathologyOutlines.com, Inc.

Reviewer: David Lucas, M.D., University of Michigan Health Systems (January 2009)

Revised: 14 June 2009, last major update June 2009

 

Definition

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● Benign tumor of mature adipocytes and mature smooth muscle

● First described in 1991 (AJSP 1991;15:121)

 

Terminology

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● Called lipoleiomyoma in uterus

● Note: myelolipoma is tumor with hematopoietic (including myeloid) elements, often in adrenal gland

 

Epidemiology

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● Very rare tumor of adults in abdomen, retroperitoneum or abdominal wall

 

Case reports

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● 34 year old woman with tumor of iliac fossa (World J Surg Oncol 2005;3:72)

● 55 year old woman with tumor presenting as inguinal hernia (Radiology Case Reports 2006, Vol 1, No 1)

 

Treatment and prognosis

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● Excision

● Does not recur, metastasize or transform

 

Gross description

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● Often 9 cm or more, completely or partially encapsulated, yellow-white

 

Gross images

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Large lobulated mass with thick pseudocapsule                      Fatty tissue with bands and nodules of firm white tissue                               

 

Micro description

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● Mature adipose tissue and mature (well differentiated) smooth muscle in short fascicles

● Variable fibrosis and inflammation

● No floret cells, no thick walled vessels, no necrosis, no mitotic figures

 

Micro images

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Mature fat and smooth muscle fibers                                                         

 

                                                    

Smooth muscle fibers are SMA+                                   Smooth muscle fibers are desmin+

 

Differential Diagnoses

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● Liposarcoma with heterologous elements - has lipoblasts and atypia

● Angiomyolipoma - also thick walled vessels, HMB45+

● Low grade leiomyosarcoma infiltrating fat - adipose tissue is not part of tumor, spindle cells are atypical, has mitotic activity

 

End of Soft Tissue Tumors > Myolipoma

 

 

 

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