2 October 2009 - Case #158
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This case was contributed by Geoffrey A. Talmon, M.D., University of Nebraska Medical Center, Omaha, Nebraska (USA).
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Case #158
Clinical history:
A 26 year old man presented with a soft tissue mass on the palm between the second and third metacarpal heads that originated from the ulnar aspect of the second digital nerve. The lesion was present since birth and recently began increasing in size.
The resected nerve had a 2.0 cm fusiform dilation near one end. The cut surfaces of the dilated portion were vaguely encapsulated, white and laminated with interposed yellow adipose tissue.
Microscopic images:
What is your diagnosis?
Diagnosis: Lipomatosis of nerve (fibrolipomatous hamartoma)
Discussion:
Lipomatosis of nerve (LN) is a benign lesion consisting of infiltration of nerve bundles by collagen and mature adipose tissue. It is also known as fibrolipomatous hamartoma, macrodystrophia lipomatosa and neural fibrolipoma. It was first described in 1952 and is considered a hamartomatous lesion without any syndromic association (IARC: Pathology and Genetics of Tumours of Soft Tissue and Bone, 3rd Edition, 2006).
Lipomatosis of nerve may be noted at birth but typically presents at ages 11 to 39 years with no history of antecedent trauma. For unclear reasons, it has a predilection for the median and less frequently, the ulnar nerves, although cases have been seen in the toes, cranial nerves and brachial plexus (Histopathology 1994;24:391).
It commonly presents as an asymptomatic or gradually enlarging, painless mass. It may be associated with distal sensory or motor deficits if compression atrophy occurs and is part of the differential diagnosis for carpal tunnel syndrome. ~33% of cases are associated with macrodactyly of the digit innervated by the affected nerve, a finding that is more common in females. A case of bilateral LN has been reported (Muscle Nerve 1998;21:656).
The appearance of LN by magnetic resonance is pathognomonic. T1 weighted images reveal a fatty mass that is evenly distributed between nerve bundles and seen running along individual nerves. It is often described as having a coaxial cable-like appearance on axial scans (Acta Radiol 2003;44:326).
Histologically, the mass is composed of a proliferation of mature adipose tissue and collagen that is confined by the epineurium and separates nerve bundles. Laminated perineural fibrosis, septation of the nerve fascicles and pseudo-onion bulb formation are also described as salient features. Occasionally, metaplastic bone is seen.
The differential diagnosis includes other fatty lesions affecting the nerve, notably intraneural lipomas, traumatic neuromas and diffuse lipomatosis. Intraneural lipomas are characterized by fatty tissue that displaces nerve bundles but does not separate them. Traumatic neuromas have onion bulb formation but usually lack concentric perineural fibrosis and have a high T2 signal density on magnetic resonance imaging. Diffuse lipomatosis is not confined to the epineurium.
As a hamartoma, lipomatosis of nerve has benign behavior. Treatment is somewhat controversial, ranging from excision (which many consider the mainstay of therapy) to simple division of the transverse carpal ligament to relieve symptoms (J Neurosurg 1998;89:683). Excision often requires the sacrifice of the involved nerve. Recurrence due to incomplete resection occurs in 33 - 60% of cases.
References: Orthopedics 2001;24:836, Histopathology 1994;24:391
All cases are archived on our website. To view them sorted by case number, diagnosis or category, visit our main Case of the Month page. To subscribe or unsubscribe to Case of the Month or our other email lists, click here.
This case was contributed by Geoffrey A. Talmon, M.D., University of Nebraska Medical Center, Omaha, Nebraska (USA).
at Moffitt Cancer in Tampa, Florida
Become a member of our multidisciplinary team of physicians and scientists focused on our Mission to contribute to the prevention and cure of cancer. You should be board certified in Anatomic Pathology and Molecular Pathology with experience in a multi-disciplinary university clinical setting. Licensure or eligibility in the State of Florida required.
The position will include 30% administrative time for establishing, supervising, and directing the Anatomic Pathology Molecular Laboratory, and 70% service time for the signing out of all of the molecular tests performed in the Anatomic Pathology Molecular Laboratory.
Join our team and receive rewards including a competitive salary, an outstanding lifestyle benefit package and all that Tampa Bay has to offer picturesque Gulf beaches, family-friendly attractions, professional sports teams, cultural events, and no state income tax!
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(1) We have updated the numerous Carcinoma topics in the Breast-malignant chapter with our new format that has thumbnails and better formatting.
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Visit and follow our Blog to see recent updates to the website.
(1) We have updated the numerous Carcinoma topics in the Breast-malignant chapter with our new format that has thumbnails and better formatting.
(2) Visit us at CAP, booth #102 - let us know how we can make our website more useful to you.
Visit and follow our Blog to see recent updates to the website.
Case #158
Clinical history:
A 26 year old man presented with a soft tissue mass on the palm between the second and third metacarpal heads that originated from the ulnar aspect of the second digital nerve. The lesion was present since birth and recently began increasing in size.
The resected nerve had a 2.0 cm fusiform dilation near one end. The cut surfaces of the dilated portion were vaguely encapsulated, white and laminated with interposed yellow adipose tissue.
Microscopic images:
What is your diagnosis?
Click here for diagnosis and discussion:
Diagnosis: Lipomatosis of nerve (fibrolipomatous hamartoma)
Discussion:
Lipomatosis of nerve (LN) is a benign lesion consisting of infiltration of nerve bundles by collagen and mature adipose tissue. It is also known as fibrolipomatous hamartoma, macrodystrophia lipomatosa and neural fibrolipoma. It was first described in 1952 and is considered a hamartomatous lesion without any syndromic association (IARC: Pathology and Genetics of Tumours of Soft Tissue and Bone, 3rd Edition, 2006).
Lipomatosis of nerve may be noted at birth but typically presents at ages 11 to 39 years with no history of antecedent trauma. For unclear reasons, it has a predilection for the median and less frequently, the ulnar nerves, although cases have been seen in the toes, cranial nerves and brachial plexus (Histopathology 1994;24:391).
It commonly presents as an asymptomatic or gradually enlarging, painless mass. It may be associated with distal sensory or motor deficits if compression atrophy occurs and is part of the differential diagnosis for carpal tunnel syndrome. ~33% of cases are associated with macrodactyly of the digit innervated by the affected nerve, a finding that is more common in females. A case of bilateral LN has been reported (Muscle Nerve 1998;21:656).
The appearance of LN by magnetic resonance is pathognomonic. T1 weighted images reveal a fatty mass that is evenly distributed between nerve bundles and seen running along individual nerves. It is often described as having a coaxial cable-like appearance on axial scans (Acta Radiol 2003;44:326).
Histologically, the mass is composed of a proliferation of mature adipose tissue and collagen that is confined by the epineurium and separates nerve bundles. Laminated perineural fibrosis, septation of the nerve fascicles and pseudo-onion bulb formation are also described as salient features. Occasionally, metaplastic bone is seen.
The differential diagnosis includes other fatty lesions affecting the nerve, notably intraneural lipomas, traumatic neuromas and diffuse lipomatosis. Intraneural lipomas are characterized by fatty tissue that displaces nerve bundles but does not separate them. Traumatic neuromas have onion bulb formation but usually lack concentric perineural fibrosis and have a high T2 signal density on magnetic resonance imaging. Diffuse lipomatosis is not confined to the epineurium.
As a hamartoma, lipomatosis of nerve has benign behavior. Treatment is somewhat controversial, ranging from excision (which many consider the mainstay of therapy) to simple division of the transverse carpal ligament to relieve symptoms (J Neurosurg 1998;89:683). Excision often requires the sacrifice of the involved nerve. Recurrence due to incomplete resection occurs in 33 - 60% of cases.
References: Orthopedics 2001;24:836, Histopathology 1994;24:391
