Age / Sex : 39 / M

Chief complaint: A soft lump in the palm of the second
metacarpal joint area of right hand and radial aspect of right second finger

1) What is your impression?

Two weeks later, you can see the final diagnosis with a brief discussion of this case.

(Quiz는 quiz일 뿐이오니 답안은 한개만 보내주시기 바라오며, 복수의 답안을 보내주시는 분은 정답이 포함되어 있더라도 부득이 semi-correct answer로 처리토록 하겠습니다.)

Courtesy: 정지영(Jung Jee Young), 중앙대병원(Chungang University Hospital)

Fibrolipomatous hamartoma of digital branch of the median nerve

Discussion

Findings:

Radiograph showed
soft tissue bulging in radial aspect of right second finger at the level of
proximal phalanx without bony abnormalities. MR imaging of the right hand
showed a well-circumscribed mass with fat signal intensity around enlarged
proper digital branch of median nerve from metacarpal shaft to proximal
phalangeal shaft level of second finger. T1- and T2-weighted images showed that
serpentine nerve bundles of low signal intensity were embedded within excessive
fatty tissue, which appeared hyperintense. Fat-suppressed T1 weighted images
with gadolinium enhancement show non-enhancing hypointense fat tissue around
nerve.

Diagnosis:

He
underwent debulking surgery. The histologic examination showed that mass
contained fibrous and lipomatous components and confirmed the diagnosis of
fibrolipomatous hamartoma.

Discussion:

Fibrolipomatous hamartoma (FLH) of the nerve
is rare, benign lesion, accounts less than 1% of benign soft tissue tumor. FLH
is characterized by diffuse enlargement of a nerve, caused by overgrowth and
fibrofatty tissue proliferation within the epineurium, perineurium, and
endoneurium. In patients with FLH, 27-66% may have associated macrodactyly,
which is referred to as macrodystrophia lipomatosa. Macrodystrophia lipomatosa
is characterized by diffuse enlargement of the digits, caused by fatty
infiltration and hypertrophy of all components of the digit, including skin,
bone, and nerves. FLH is most commonly involve the median nerve and its digital
branches followed by the ulnar nerve, radial nerve, brachial plexus, nerves of
the lower extremity and cranial nerves. MR imaging demonstrates serpiginous low
intensity structures on all sequences, which representing thickened nerve
fascicles surrounded by or embedded in excessive fatty tissue. These findings
resemble a coaxial cable on axial images and the nerve bundles could be shown a
spaghetti-like appearance on coronal images. Differential diagnosis of FLH from
other nerve sheath tumor is generally not difficult. Intraneural lipoma is
primary considerable tumor of differentiation with FLH and is a focal fatty
mass, separated from the individual nerve bundles in comparison with the even
fatty distribution characteristic on FLH on MR imaging. Other considerable
tumors are peripheral nerve sheath tumor (schwannoma and neurofibroma),
intraneural hemangioma. Treatment of FLH has not been established and still
controversial because the tumor cannot be completely excised without
sacrificing the involved nerve.

References:

1.   
Silverman TA,
Enzinger FM. Fibrolipomatous hamartoma of nerve. A clinicopathologic analysis
of 26 cases. Am J Surg Pathol 1985;9:7-14

2.   
Marom EM, Helms
CA. Fibrolipomatous hamartoma: Pathognomonic on mr imaging. Skeletal Radiol
1999;28:260-264

3.   
Toms AP, Anastakis
D, Bleakney RR, Marshall TJ. Lipofibromatous hamartoma of the upper extremity:
A review of the radiologic findings for 15 patients. AJR Am J Roentgenol
2006;186:805-811

4.   
Boren WL, Henry
RE, Jr., Wintch K. Mr diagnosis of fibrolipomatous hamartoma of nerve:
Association with nerve territory-oriented macrodactyly (macrodystrophia
lipomatosa). Skeletal Radiol 1995;24:296-297

5.   
Murphey MD, Smith
WS, Smith SE, Kransdorf MJ, Temple HT. From the archives of the afip. Imaging
of musculoskeletal neurogenic tumors: Radiologic-pathologic correlation.
Radiographics 1999;19:1253-1280