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Fibrolipomatous hamartoma, also designated as neural fibrolipoma or lipofibromatous hamartoma, is an anomalous growth of fibroadipose tissue of the peripheral nerve sheath. Some cases are associated with macrodactyly. This disorder usually affects nerves in the upper extremities, most commonly the median nerve1-3. Involvement of other nerves is rare.
Magnetic resonance imaging of this disorder is diagnostic, obviating the need for biopsy4-6. The unique longitudinally oriented, cylindrical regions of signal void are thought to represent nerve fascicles with perineural fibrosis. However, this speculation has not been proven because radical excision of the affected nerve is usually impossible. Treatment of this disorder is controversial. Severe motor and sensory deficits have been reported after attempted surgical excision3.
We report two unusual cases of fibrolipomatous hamartoma of the foot, with emphasis on preoperative diagnosis by magnetic resonance imaging and successful surgical treatment. Comparison between the histological specimens and the magnetic resonance images clearly showed that the signal void on the magnetic resonance images represented nerve fascicles with surrounding fibrosis.
Case Reports
CASE 1. A sixteen-year-old girl presented with a slowly growing plantar mass in the right foot that had been present for ten years. Neither the patient nor members of her family had a history of neurofibromatosis or other soft-tissue tumors. She had no pain at rest, but she had shooting pain while running or while walking on tiptoe. Physical examination revealed a 7 x 3-cm mobile, tender mass located in the plantar soft tissue at the level of the distal first metatarsal and extending to the lateral side of the great toe. She had no symptoms or signs of vascular or neurological compromise. Magnetic resonance images confirmed the presence of the mass with both fatty and fibrous elements. At the level of the distal metatarsals, the tumor was composed of fatty elements and bundles of small areas of signal void (Fig. I-A). Because of these characteristic magnetic resonance imaging findings and clinical symptoms, a preoperative diagnosis of fibrolipomatous hamartoma of the medial plantar nerve was made.
Nonoperative and operative treatment methods were discussed with the patient and her family. Because the branches of the medial plantar nerve at the level of the metatarsophalangeal joint (the proper digital nerve of the great toe) have no motor function, we informed...