Soft tissue
Adipose tissue
Intramuscular lipoma

Author: Charanjeet Singh, M.D. (see Authors page)

Revised: 28 July 2016, last major update June 2012

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Intramuscular lipoma

Definition / General
  • Lipoma that infiltrates within muscle belly
  • Called intermuscular lipoma if between muscle fascicles
Terminology
  • Also called invasive or infiltrative lipoma
  • Not a WHO diagnosis
Sites
  • Intramuscular: affects thigh, trunk, head and neck of middle-aged adults
  • Intermuscular: affects abdominal wall of middle-aged adults; doesn’t recur if completely excised
Clinical Features
  • Benign, but 20% recur due to incomplete excision
  • Infiltration may be due to muscular degeneration and endomysial fatty growth secondary to atrophy (BMC Musculoskelet Disord 2004;18:20)
Case Reports
Clinical Images

Images hosted on other servers:

Tumor of face

Gross Description
  • Intramuscular: poorly circumscribed, extends between and around skeletal muscle fibers
Gross Images

Images hosted on PathOut servers:

Yellow adipose tissue within skeletal muscle



Images hosted on other servers:

Irregular lobulated tumor without encapsulation

Yellow adipose tissue within skeletal muscle

Micro Description
  • Mature lipocytes that infiltrate skeletal muscle
  • No atypia, no mitotic figures
Micro Images

Images hosted on PathOut servers:

Adipocytes and atrophic muscle



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Prominent muscular atrophy

Adipocytes and atrophic muscle

Intramuscular lipoma

Differential Diagnosis