Age / Sex : 4 / F

Age / Sex : 4 years/ female

Chief complaint : Mass lesion and widening of first webspace of right foot

1) What is your impression?

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

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Courtesy : In Sook Lee, MD. Pusan National University Hospital

Lipomatosis of nerve

Discussion

Findings:

Anteroposterior radiograph of foot shows enlargement of great toe and widening of 1st web space accompanying soft tissue mass with smooth contour bulging pattern.

Coronal T1- and T2-weighted images show heterogeneous lipomatous mass mainly involving 1st webspace.

On fat suppressed contrast enhanced axial T1-weighted images, the mass reveals thin peripheral and septal enhancement in the 1st web space extending into the lateral aspect of great toe and subcutaneous layer of plantar aspect.

Differential Diagnosis:

Neurofibromatosis

Other benign fatty mass such as lipoblastoma

Diagnosis:  Neural fibrolipoma

Discussion:

 Neural fibrolipoma (fibrolipomatous hamartoma of nerve, perineural lipoma, and intraneural lipoma) is a rare lesion related to the gradual infiltration of major nerves and their branches by fibrofatty tissue. It is typically present during children, adolescents, or early adulthood with a soft, slowly enlarging mass in the volar aspect of the hand, wrist, or forearm.

Accompanying symptoms include pain, tenderness, decreased sensation, and paresthesia. Approximately one-third of patients have macrodactyly, referred to as macrodystrophia lipomatosa, usually involving the second or third digits of the hand or foot. Multiple digits may be involved.

In the upper extremity, macrodystrophia lipomatosa most commonly is located in the distribution of the median nerve. In macrodactyly, the phalanges are endosteal bone deposition, resulting in increase in increase in osseous size and width.

Radiographs demonstrate both bone and soft tissue abnormalities. A mass with increased lucency relative to surrounding soft tissues, which corresponds to fibrofatty proliferation may be seen. The phalanges are long, broad, and often splayed at their distal ends. The osseous overgrowth may be disproportionately large, with extensive secondary degenerative change.

MR imaging reveals features of both fibrous and fatty tissue, and a serpentine appearance of the enlarged nerves is distinctive.

 The differential diagnosis of localized gigantism includes Klippel-Trenaunay-Weber syndrome, neurofibromatosis, chronic vascular stimulation (which tends to be more symmetric), lymphangioma, soft tissue hemangioma, enchondromatosis and Proteus syndrome.

References:

1.       Kransdorf MJ, Moser RP Jr, Meis JM, Meyer CA. Fat containing soft-tissue masses of the extremities. RadioGraphics 1991; 11 (1): 81-106
2.       Ly JQ, Bui-Mansfield LT, SanDiego JW, Beaman NA, Ficke JR. Neural fibrolipoma of the foot. J Comput Assist Tomogr 2003;27:639-640
3.       Murphey MD, Smith WS, Smith SE, Kransdorf MJ, Temple HT. From the archives of the AFIP. Imaging of the musculoskeletal neurogenic tumors: radiologic-pathologic correlation. Radiographics 1999;19:1253-1280