Fibrolipomatous hamartoma in the foot: atypical MR imaging findings

Macrodystrophia Lipomatosa of the Foot: A Case Report of MRI and Histologic Findings Including Pacinian Corpuscle Abnormalities

CASE

A 37-year-old man presented with pain and macrodactyly of a toe. Imaging and histology demonstrated findings consistent with macrodystrophia lipomatosa (MDL). We compared our findings with control tissue obtained from an identical site of a fresh-frozen cadaveric foot from the same anatomical site. Pacinian corpuscles (PCs) in the MDL tissue were increased in number, size, and shape compared with the control tissue and demonstrated edematous interstitial lamellae and vacuolar degenerative change. We also document the magnetic resonance imaging findings of the PCs.

CONCLUSION

Peculiar abnormalities of PCs in MDL underline nerve damage and may be a contributing factor in the pain associated with this unusual condition.

Lipomatosis of interdigital nerves: Unusual localization

Lipomatosis of the nerve (LN) is a rare benign tumor that is characterized by proliferating fibrous fatty tissue surrounding and infiltrating the peripheral nerves. While there are numerous case reports of LN affecting the median nerve and its branches, there are few reports, to the authors' knowledge, of their occurrence in the foot and ankle. A rare case of LN involving the second and third interdigital nerve in a 41-year-old man, which was successfully treated with surgical excision, is reported.

Lipofibromatous Hamartoma of the Plantar Nerve An Extremely Rare Localization

Lipofibromatous hamartoma (LFH) is a rare, benign, tumor-like soft-tissue lesion that affects the peripheral nerves and forms a palpable neurogenic mass. Lipofibromatous hamartoma is associated with pain and sensory and/or motor deficits in the area of innervation of the affected nerve. This report describes a rare case of LFH of the plantar nerve. A 48-year-old woman presented to our outpatient orthopedic clinic with pain and a burning sensation on her left foot. The patient had a history of Morton's neuroma and had undergone a tarsal tunnel operation 2 years earlier at another center. None of her symptoms was alleviated by two previous operations. Magnetic resonance imaging with contrast revealed tenosynovitis of the flexor hallucis longus tendon and signal changes at deep tissue planes of the foot at the levels of the second and third toes, on the dorsal site and subcutaneous soft-tissue planes, suggesting edema and Morton's neuroma. The lesion was excised under spinal anesthesia, and histopathologic examination of the specimen revealed a diagnosis of LFH. The patient was discharged without any symptoms and her foot was normal at 8-month outpatient follow-up, with no indications of postoperative complications and/or recurrence.

Fat-containing soft-tissue masses in children

The diagnosis of soft-tissue masses in children can be difficult because of the frequently nonspecific clinical and imaging characteristics of these lesions. However key findings on imaging can aid in diagnosis. The identification of macroscopic fat within a soft-tissue mass narrows the differential diagnosis considerably and suggests a high likelihood of a benign etiology in children. Fat can be difficult to detect with sonography because of the variable appearance of fat using this modality. Fat is easier to recognize using MRI, particularly with the aid of fat-suppression techniques. Although a large portion of fat-containing masses in children are adipocytic tumors, a variety of other tumors and mass-like conditions that contain fat should be considered by the radiologist confronted with a fat-containing mass in a child. In this article we review the sonographic and MRI findings in the most relevant fat-containing soft-tissue masses in the pediatric age group, including adipocytic tumors (lipoma, angiolipoma, lipomatosis, lipoblastoma, lipomatosis of nerve, and liposarcoma); fibroblastic/myofibroblastic tumors (fibrous hamartoma of infancy and lipofibromatosis); vascular anomalies (involuting hemangioma, intramuscular capillary hemangioma, phosphate and tensin homologue (PTEN) hamartoma of soft tissue, fibro-adipose vascular anomaly), and other miscellaneous entities, such as fat necrosis and epigastric hernia.

Neural Fibrolipoma of the Ankle: A Case Report and Review of the Literature

Neural fibrolipomas are exceedingly rare benign tumors composed of hypertrophied fibrofatty tissue intermixed with nerve tissues. Our review of the published data identified only 15 cases of this tumor involving the foot and/or ankle region. An otherwise healthy 35-year-old male was referred for evaluation of a painless soft tissue mass present in the anterior left ankle. The mass had been present for approximately 6 to 7 years and had recently increased in size. Physical examination demonstrated a prominent, fluctuant mass present in the left ankle measuring 4 cm in diameter. The mass was not well-defined, was immobile, and did not transilluminate. No gross pedal deformity was present. Radiographic imaging revealed increased soft tissue prominence and density to the anterior ankle without bone involvement. Magnetic resonance imaging demonstrated a mass isointense to fat on all sequences without contrast enhancement, suggestive of a lipoma. Surgical excision was performed; the mass was yellow and lipomatous in nature. The mass was intimately associated with the superficial peroneal nerve, which had to be sacrificed during excision. The pathologic examination of the mass revealed findings consistent with a neural fibrolipoma. The patient healed uneventfully without recurrence. His only complaint was of some residual numbness in the medial foot.

Atypical Presentation of Fibrolipomatous Hamartoma of Superficial Peroneal Nerve

Fibrolipomatous hamartoma is a rare presentation in the foot. An accurate diagnosis is key, with magnetic resonance imaging findings considered definitive. The management is dependent on the symptoms. We present an atypical presentation of fibrolipomatous hamartoma of the superficial peroneal nerve and discuss the current published data.

Fibrolipomatous hamartoma of the median nerve

Fibrolipomatous hamartoma is a rare benign tumour most commonly affecting the median nerve and is characterised by fibro-fatty nerve infiltration. It results in fusiform nerve enlargement with a pathognomonic ‘spaghetti-like’ imaging appearance. Patients present with numbness and paraesthesia and later with motor deficits in the affected nerve distribution. The condition frequently coexists with macrodystrophia lipomatosa in up to two-thirds of cases.

Lipomatosis of the sciatic nerve secondary to compression by a desmoid tumor

Lipomatosis of nerve is a rare benign tumor-like process characterized by infiltration of the epineurium by adipose and fibrous tissue leading to nerve enlargement. We describe a case of lipomatosis of the sciatic nerve compressed by an adjacent desmoid tumor. This case supports the hypothesis that lipomatosis of nerve may form as a result of irritation or compression by adjacent structures.

Fibrolipomatous hamartoma of the inferior calcaneal nerve (Baxter nerve)

Fibrolipomatous hamartoma (FLH) is a rare, benign lesion of the peripheral nerves most frequently involving the median nerve and its digital branches (80 %). Pathognomonic MR features of FLH such as coaxial-cable-like appearance on axial planes and a spaghetti-like appearance on coronal planes have been described by Marom and Helms, obviating the need for diagnostic biopsy. We present a case of fibrolipomatous hamartoma of the inferior calcaneal nerve (Baxter nerve) with associated subcutaneous fat proliferation.

Adipose lesions of nerve: the need for a modified classification

OBJECT

Adipose lesions of nerve are rare and poorly understood. Their current classification, although not universally accepted, generally includes lipomatosis of nerve with or without localized macrodactyly, and intra- as well as extraneural lipoma. The authors believe that the spectrum of these lesions and their interrelationships are not currently appreciated. They propose an adaptation to the existing framework to illustrate the expanding spectrum of adipose lesions of nerve by considering lipomatosis and lipoma singly or in combination.

METHODS

Fourteen representative cases are presented to demonstrate not only the intraneural and extraneural examples of lipomatosis and lipoma, but also their anatomical combinations.

RESULTS

Based on the cases presented and a careful literature review, a conceptual approach to the classification of adipose lesions of nerve is generated. This approach incorporates the 2 essential lesions, lipomatosis of nerve and lipoma, in both their intra- and extraneural forms. This permits expansion to encompass combinations.

CONCLUSIONS

To press the concept that adipose tumors of nerve are a broad but interrelated spectrum of lesions, the authors propose modification of the present classification system. This approach provides an orderly platform for progress, reflects understanding of these interrelated lesions, and facilitates optimal treatment by distinguishing resectable from nonresectable components.

Peripheral tumor and tumor-like neurogenic lesions

Neoplasms of neurogenic origin account for about 12% of all benign and 8% of all malignant soft tissue neoplasms. Traumatic neuroma, Morton neuroma, lipomatosis of a nerve, nerve sheath ganglion, perineurioma, benign and malignant peripheral nerve sheath tumors (PNST) are included in this group of pathologies. Clinical and radiologic evaluation of patients with neurogenic tumors and pseudotumors often reveals distinctive features. In this context, advanced imaging techniques, especially ultrasound (US) and magnetic resonance (MR) play an important role in the characterization of these lesions. Imaging findings such as location of a soft tissue mass in the region of a major nerve, nerve entering or exiting the mass, fusiform shape, abnormalities of the muscle supplied by the nerve, split-fat sign, target sign and fascicular appearance should always evoke a peripheric nerve sheath neoplasm. Although no single imaging finding or combination of findings allows definitive differentiation between benign from malign peripheric neurogenic tumors, both US and MR imaging may show useful features that can lead us to a correct diagnosis and improve patient treatment. Traumatic neuromas and Morton neuromas are commonly associated to an amputation stump or are located in the intermetatarsal space. Lipomatosis of a nerve usually appears as a nerve enlargement, with thickened nerve fascicles, embedded in evenly distributed fat. Nerve sheath ganglion has a cystic appearance and commonly occurs at the level of the knee. Intraneural perineuroma usually affects young people and manifests as a focal and fusiform nerve enlargement. In this article, we review clinical characteristics and radiologic appearances of these neurogenic lesions, observing pathologic correlation, when possible.

Carpal tunnel syndrome due to fibrolipomatous hamartoma of the median nerve

Nervous lipofibromatous hamartoma is a rare tumor-like condition involving the peripheral nerves, whereby the epineurium and perineurium are enlarged and distorted by excess of fatty and fibrous tissues that infiltrate between and around nerve boundaries. The median nerve is much more likely to develop a hamartoma than other nerves with a predilection for the carpal tunnel. We present a case of carpal tunnel syndrome in an adult caused by fibrolipomatous hamartoma of the median nerve, successfully removed by excision of the fibrolipomatous tissue and decompression.

MRI diagnosis of fibrolipomatous hamartoma of the median nerve and associated macrodystrophia lipomatosa

Fibrolipomatous hamartoma is an uncommon congenital disorder, which is characterized by disproportionate hyperplasia of adipose tissue infiltrating along the perineurium, the epineurium and the affected nerve trajectory. We present a case of combined fibrolipomatous hamartoma and macrodystrophia lipomatosa of the median nerve. The involved sites included the left palm, wrist and forearm. Part of the patient's middle finger had been amputated due to previous macrodystrophia lipomatosa; however, the lesion continued to enlarge and was accompanied by numbness. Magnetic resonance imaging demonstrated a typical fibrolipomatous hamartoma with high signal intensity of fat on both T1-weighted and T2-weighted images, characteristic coaxial cable appearance on axial images, and spaghetti appearance on sagittal images. A similar skipped lesion at the median nerve of the middle forearm was also noted. To the best of our knowledge, this has not been reported in the English literature.

Fibrolipomatous hamartoma of median nerve

Fibrolipomaous hamartoma is a benign neoplasm of nerves, resulting from anomalous growth of fibroadipose tissue of the nerve sheath. The median nerve is the most commonly involved nerve. Magnetic resonance imaging (MRI) features are pathognomonic, showing a coaxial cable-like appearance on axial images and spaghetti-like appearance on coronal images. Preferred management of the lesion is conservative.

Lipofibromatous hamartoma of nerve

Lipofibromatous hamartoma is an uncommon, benign, fibrofatty tumor that can involve peripheral nerve tissue. We report a rare neural lipofibroma of the foot in a 6-year-old boy.

Fibrolipoma of the median nerve

Neural fibrolipoma or fibrolipomatous hamartoma is an uncommon benign tumor that usually arises in the median nerve. Fibrofatty tissue proliferates around the nerve and infiltrates the epineurium and perineurium. We report a case of fibrolipomatous hamartoma of the left median nerve in an 18-year-old woman. Our objective was to describe the pathognomonic magnetic resonance imaging features, whose presence obviates the need for a diagnostic biopsy.

Lipomatosis of the sciatic nerve: typical and atypical MRI features

Lipomatosis of nerve, also known as fibrolipomatous hamartoma, is a rare condition of nerve, usually affecting the median nerve. The MRI appearance is characteristic. We describe two cases of lipomatosis of nerve involving the sciatic nerve, an extremely unusual location for this lesion, in patients with sciatic neuropathy. These cases share the typical features previously described in the literature for other nerves, but also contain atypical features not previously highlighted, relating to the variability in distribution and extent of the fatty deposition. Recognition of the MRI appearance of this entity is important in order to avoid unnecessary attempts at surgical resection of this lesion.