Intermuscular lipoma

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Intermuscular lipomas are lipomas located deep between muscles.

Terminology

Intermuscular lipomas are sometimes called ‘infiltrating lipoma’ since they can involve both the intramuscular and the tissue between muscles .

Epidemiology

Intermuscular lipomas are much less common than superficial lipomas and are found most often in middle-aged patients from the 4 to 6 decades of life, with men being more commonly affected .

Clinical presentation

They might be found incidentally or patients might present with a palpable nonspecific lump. They are usually larger on clinical presentation than superficial lipomas .

Pathology

Lipomas consist of mature adipocytes identical to normal adult fatty tissue .

Location

Intermuscular lipomas are most often found between large muscles of the following locations :

  • lower extremity
  • trunk
  • shoulder
  • upper extremity

Intermuscular lipomas of the chest wall hand and feet are rare as well as in the retroperitoneum.

Macroscopic appearance

Intermuscular lipomas are usually yellowish, well-circumscribed lesions surrounded by a thin capsule located between muscles .

Microscopic appearance

Adipocytes usually of larger size possibly with microscopic, neighboring muscular infiltration .

Radiographic features

Plain radiograph

A large intermuscular lipoma can appear as lucency on plain radiograph.

CT

Intermuscular lipomas usually show the following features :

  • homogeneous, hypodense soft tissue mass within the musculature
  • typically with Hounsfield measurements in the -60 to -120 range
  • frequently show thin septae
MRI

Usually shows a fat-containing homogenous mass within a muscle, which is isointense to subcutaneous fat in all sequences, frequently showing subtle thin intralesional septae .

Signal characteristics
  • T1: homogenous, high signal intensity
  • T2: homogenous, high signal intensity
  • T2FS/IMFS: homogenous, low signal intensity
  • T1C+: no enhancement, except for possible subtle enhancement of the fibrous capsule

Treatment and prognosis

Treatment options depend on tumor size location symptoms and overall patient condition and include wide resection, which is curative.

Differential Diagnosis

Differential diagnosis includes the following :

See also