Intramuscular lipoma
Updates to Article Attributes
An intramuscular lipoma is a deep-seated lipoma located within a muscle.
Terminology
Intramuscular lipomas share the term ‘infiltrating lipoma’ with intermuscular lipomas.
Epidemiology
Intramuscular lipomas account for about 1% of all lipomas and occur in all age groups with the most occurring between the 5th to 7th decades of life. There seems to be a female predominance 1.
Clinical presentation
Patients might present with unspecific swelling of the tumour might be found incidentally. Rare presentations are pain or paresthesias due to nerve entrapment 1,2.
Pathology
Intramuscular lipomas consist of mature adipocytes identical to normal adult fatty tissue 1, the exact aetiology remains unclear.
Subtypes
- infiltrative
- well defined or circumscribed
Location
They can occur at any anatomical site but are believed to occur mainly in the large muscles of the limbs and the trunk, an exact anatomical distribution, however, has not been established. Intramuscular lipomas of hand and feet are rare though 1.
Macroscopic appearance
Intramuscular lipomas are usually yellowish are located within muscle and may show a capsule at the extra muscular margin can show interdigitations and muscle fibres passing through 1.
Microscopic appearance
Mature adipocytes irregularly infiltrate and replace muscle fibres and bundles in the infiltrative type 1. There is no fatty infiltration of adjacent muscle typically observed in the well-defined or well-circumscibed-circumscribed type.
Radiographic features
Plain radiograph
An intramuscular lipoma can appear as lucency, especially if large and can show radioopaque streaks.
Ultrasound
- hyperechoic well-defined mass with fine internal echoes or striated appearance due to interdigitations of muscular tissue
CT
Intramuscular lipomas usually show the following features 1:
- hypodense soft tissue mass within the musculature
- typically with Hounsfield measurements in the negative range
- can show striated appearance
- can show thick intramuscular septae and interdigitations
- usually, oval or fusiform shape but can vary
MRI
Usually shows either a fat-containing mass within a muscle, which is isointense to subcutaneous fat in all sequences sometimes with septae. Septae should not enhance avidly however or show nodules 2. Interlocked or intermingled muscular tissue and fibres can be observed in the infiltrative type 1. If a capsule is present and found outside the intramuscular lipoma, there should not be muscular fibres in the main mass 1.
Treatment and prognosis
Treatment depends on tumour size location and symptoms, and include watchful waiting or wide resection.
Differential Diagnosisdiagnosis
- well-differentiated liposarcoma (dumb-bell shaped, should be suspected if septae markedly enhance)
See also
-<p>An<strong> intramuscular lipoma </strong>is a deep-seated <a title="Lipoma" href="/articles/lipoma">lipoma</a> located within a muscle.</p><h4>Terminology</h4><p>Intramuscular lipomas share the term ‘infiltrating lipoma’ with intermuscular lipomas.</p><h4>Epidemiology</h4><p>Intramuscular lipomas account for about 1 % of all lipomas and occur in all age groups with the most occurring between the 5<sup>th</sup> to 7<sup>th</sup> decades of life. There seems to be a female predominance <sup>1</sup>.</p><h4>Clinical presentation</h4><p>Patients might present with unspecific swelling of the tumour might be found incidentally. Rare presentations are pain or paresthesias due to nerve entrapment <sup>1,2</sup>.</p><h4>Pathology</h4><p>Intramuscular lipomas consist of mature adipocytes identical to normal adult fatty tissue <sup>1</sup>, the exact aetiology remains unclear.</p><h5>Subtypes</h5><ul>- +<p>An<strong> intramuscular lipoma </strong>is a deep-seated <a href="/articles/lipoma">lipoma</a> located within a muscle.</p><h4>Terminology</h4><p>Intramuscular lipomas share the term ‘infiltrating lipoma’ with <a title="Intermuscular lipoma" href="/articles/intermuscular-lipoma">intermuscular lipomas</a>.</p><h4>Epidemiology</h4><p>Intramuscular lipomas account for about 1% of all lipomas and occur in all age groups with the most occurring between the 5<sup>th</sup> to 7<sup>th</sup> decades of life. There seems to be a female predominance <sup>1</sup>.</p><h4>Clinical presentation</h4><p>Patients might present with unspecific swelling of the tumour might be found incidentally. Rare presentations are pain or paresthesias due to nerve entrapment <sup>1,2</sup>.</p><h4>Pathology</h4><p>Intramuscular lipomas consist of mature adipocytes identical to normal adult fatty tissue <sup>1</sup>, the exact aetiology remains unclear.</p><h5>Subtypes</h5><ul>
-</ul><h5>Location</h5><p>They can occur at any anatomical site but are believed to occur mainly in the large muscles of the limbs and the trunk, an exact anatomical distribution, however, has not been established. Intramuscular lipomas of hand and feet are rare though <sup>1</sup>.</p><h5>Macroscopic appearance</h5><p>Intramuscular lipomas are usually yellowish are located within muscle and may show a capsule at the extra muscular margin can show interdigitations and muscle fibres passing through <sup>1</sup>.</p><h5>Microscopic appearance</h5><p>Mature adipocytes irregularly infiltrate and replace muscle fibres and bundles in the infiltrative type <sup>1</sup>. There is no fatty infiltration of adjacent muscle typically observed in the well-defined or well-circumscibed type.</p><h4>Radiographic features</h4><h5>Plain radiograph</h5><p>An intramuscular lipoma can appear as lucency, especially if large and can show radioopaque streaks.</p><h5>Ultrasound</h5><ul><li>hyperechoic well-defined mass with fine internal echoes or striated appearance due to interdigitations of muscular tissue</li></ul><h5>CT</h5><p>Intramuscular lipomas usually show the following features <sup>1</sup>:</p><ul>- +</ul><h5>Location</h5><p>They can occur at any anatomical site but are believed to occur mainly in the large muscles of the limbs and the trunk, an exact anatomical distribution, however, has not been established. Intramuscular lipomas of hand and feet are rare though <sup>1</sup>.</p><h5>Macroscopic appearance</h5><p>Intramuscular lipomas are usually yellowish are located within muscle and may show a capsule at the extra muscular margin can show interdigitations and muscle fibres passing through <sup>1</sup>.</p><h5>Microscopic appearance</h5><p>Mature adipocytes irregularly infiltrate and replace muscle fibres and bundles in the infiltrative type <sup>1</sup>. There is no fatty infiltration of adjacent muscle typically observed in the well-defined or well-circumscribed type.</p><h4>Radiographic features</h4><h5>Plain radiograph</h5><p>An intramuscular lipoma can appear as lucency, especially if large and can show radioopaque streaks.</p><h5>Ultrasound</h5><ul><li>hyperechoic well-defined mass with fine internal echoes or striated appearance due to interdigitations of muscular tissue</li></ul><h5>CT</h5><p>Intramuscular lipomas usually show the following features <sup>1</sup>:</p><ul>
-</ul><h5>MRI</h5><p>Usually shows either a fat-containing mass within a muscle, which is isointense to subcutaneous fat in all sequences sometimes with septae. Septae should not enhance avidly however or show nodules <sup>2</sup>. Interlocked or intermingled muscular tissue and fibres can be observed in the infiltrative type <sup>1</sup>. If a capsule is present and found outside the intramuscular lipoma, there should not be muscular fibres in the main mass <sup>1</sup>.</p><h4>Treatment and prognosis</h4><p>Treatment depends on tumour size location and symptoms, and include watchful waiting or wide resection.</p><h4>Differential Diagnosis</h4><ul><li>well-differentiated liposarcoma (dumb-bell shaped, should be suspected if septae markedly enhance)</li></ul><h4>See also</h4><ul>- +</ul><h5>MRI</h5><p>Usually shows either a fat-containing mass within a muscle, which is isointense to subcutaneous fat in all sequences sometimes with septae. Septae should not enhance avidly however or show nodules <sup>2</sup>. Interlocked or intermingled muscular tissue and fibres can be observed in the infiltrative type <sup>1</sup>. If a capsule is present and found outside the intramuscular lipoma, there should not be muscular fibres in the main mass <sup>1</sup>.</p><h4>Treatment and prognosis</h4><p>Treatment depends on tumour size location and symptoms, and include watchful waiting or wide resection.</p><h4>Differential diagnosis</h4><ul><li>well-differentiated <a title="Liposarcoma" href="/articles/liposarcoma">liposarcoma</a> (dumb-bell shaped, should be suspected if septae markedly enhance)</li></ul><h4>See also</h4><ul>
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