Neural lipofibromatous hamartoma: a report of two cases and review of the literature

PIK3CA mutations in lipomatosis of nerve with or without nerve territory overgrowth

Lipomatosis of nerve is a rare malformation characterized by a fibrolipomatous proliferation within peripheral nerve. Lipomatosis of nerve most frequently involves the median nerve, and manifests clinically as a compressive neuropathy. However, 30-60% of cases are associated with tissue overgrowth within the affected nerve's territory (e.g., macrodactyly for lipomatosis of nerve in the distal median nerve). Somatic activating PIK3CA mutations have been identified in peripheral nerve from patients with lipomatosis of nerve with type I macrodactyly, which is now classified as a PIK3CA-related overgrowth spectrum disorder. However, the PIK3CA mutation status of histologically confirmed lipomatosis of nerve, including cases involving proximal nerves, and cases without territory overgrowth, has not been determined. Fourteen histologically confirmed cases of lipomatosis of nerve involving the median (N = 6), brachial plexus (N = 1), ulnar (N = 3), plantar (N = 2), sciatic and superficial peroneal nerves (N = 1 each) were included. Ten cases had nerve territory overgrowth, ranging from macrodactyly to hemihypertrophy; and four cases had no territory overgrowth. Exome sequencing revealed "hotspot" activating PIK3CA missense mutations in 6/7 cases. Droplet digital polymerase chain reaction for the five most common PIK3CA mutations (p.H1047R, p.H1047L, p.E545K, p.E542K, and p.C420R) confirmed the exome results and identified an additional six cases with mutations (12/14 total). PIK3CA mutations were found in 8/10 cases with territory overgrowth (N = 7 p.H1047R and N = 1 p.E545K), including two proximal nerve cases with extremity overgrowth, and 4/4 cases without territory overgrowth (p.H1047R and p.H1047L, N = 2 each). The variant allele frequency of PIK3CA mutations (6-32%) did not correlate with the overgrowth phenotype. Three intraneural lipomas had no detected PIK3CA mutations. As PIK3CA mutations are frequent events in lipomatosis of nerve, irrespective of anatomic site or territory overgrowth, we propose that all phenotypic variants of this entity be classified within the PIK3CA-related overgrowth spectrum and termed "PIK3CA-related lipomatosis of nerve".

Recurrence of carpal tunnel syndrome in isolated non-syndromic macrodactyly: DTI examination of a giant median nerve

Macrodystrophia lipomatosa, a hamartomatous enlargement of soft tissues leading to gigantism of a part or a whole extremity, generally affects the territory of distribution of a single nerve. In some cases, this condition may cause an entrapment neuropathy. We report the clinical, radiological, and surgical findings of a patient with isolated non-syndromic macrodactyly and giant median nerve presenting recurrent carpal tunnel syndrome (CTS). In this case, conventional magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) supported the presence of fibrohamartomatous infiltration, determining an enlargement of the median nerve and consequently an increased susceptibility to compression damage. A 57-year-old man presenting macrodactyly of the second and third finger of the right hand showed recent onset of severe hypoesthesia of the first three fingers of the right hand. He also underwent surgery for right CTS 23 years before. The electromyography/electroneurography confirmed the diagnosis of CTS. The ultrasonography showed a massive enlargement of the median nerve within the carpal tunnel, while MRI confirmed the enlargement of the median nerve with thickened hypointense bundles and interposed tissue, with increased mean diffusivity and decreased fractional anisotropy at DTI. We discuss about the use of a relatively novel imaging technique, investigating for the first time an uncommon cause of a very common entrapment neuropathy.

Lipofibromatous hamartoma of the median nerve with macrodactyly of middle finger

Lipofibromatous Hamartoma (LFH) is a rare tumour affecting the peripheral nerves, mostly the median nerve. It is benign and slowly growing. Less than 100 cases have been reported in the literature, about one quarter of them are associated with macrodactyly in the field of the affected nerve. We reported a case of a 13 years old female with LFH of the median nerve at the level of the wrist associated Macrodactyly of the ipsilateral middle finger treated surgically by decompression only.

Nonepithelial Tumors and Tumor-like Lesions of the Skin and Subcutis in Children

This overview of mesenchymal tumors presenting in the skin and/or subcutis in children brings together the range of neoplasms and hamartomas which are seen in this age-group. It is not surprising from the perspective of the pediatric or general surgical pathologist that vascular anomalies, including true neoplasms and vascular malformations, are the common phenotypic category. Since there is considerable morphologic overlap among these lesions, clinicopathologic correlation may be more important than for many of the other mesenchymal tumors. The skin and subcutis are the most common sites of clinical presentation for the infantile myofibroma which is the most common of fibrous mesenchymal tumors in children. Several of the other mesenchymal tumors are more common adults-like dermatofibrosarcoma protuberans, but nonetheless have an important presence in children, even as a congenital neoplasm. A lipomatous tumor in a young child should be considered as a possible manifestation of an overgrowth syndrome.

Lipofibromatous Hamartoma of the Median Nerve: A Case Report

Lipofibromatous hamartoma is a rare and slow growing benign fibro-fatty tumor. It is characterized by the proliferation of mature adipocytes within the epineurium and the perineurium of the peripheral nerves. In the upper extremity, it most commonly affects the median nerve. Median nerve involvement commonly leads to pain, numbness, paresthesia and carpal tunnel syndrome. This article presents a case of lipofibromatous hamartoma in an 8-year-old child followed by a discussion of the epidemiology, diagnosis, imaging details and treatment options for this condition.

The first radiographic image of a peripheral nerve disorder? Lipomatous macrodactyly (unrecognized lipomatosis of nerve)

Lipomatosis of nerves (LN) involves benign fibro-fatty infiltration and is often associated with territorial overgrowth of soft tissue and bone; this distinctive disease pattern can be visualized on plain radiographs. We recently discovered a case (presented by Sir Robert Jones in 1898 to the Pathological Society of London) that indirectly represents a historical landmark in the imaging of peripheral nerves. The clinical findings and image, with obvious soft tissue and bone overgrowth, are pathognomonic for LN, making this one of the earliest radiological observations of a peripheral nerve lesion.

Lipofibromatous hamartoma of the median nerve: a comprehensive review and systematic approach to evaluation, diagnosis, and treatment

Many modalities exist for diagnosing and treating lipofibromatous hamartoma (LFH), with no clear consensus. This is the first comprehensive study to review the existing literature on LFH of the median nerve and to suggest a systematic approach to its diagnosis and treatment. An electronic and manual search was conducted on Medline, Embase, Google Scholar, Current Contents, and Science Citation Index for original and review articles in English or French, from 1946 to November 2012. After 2 levels of screening, 106 references containing case reports were retained. Data extraction included patient demographics, clinical information, diagnostic modalities, treatment, and follow-up. A total of 180 cases were reported in the literature. One third of patients had associated macrodactyly (32%). Gender distribution is equal in LFH with or without macrodactyly, with most patients (71%) presenting before age 30 years. The main presenting symptom is an enlargement (88%) over the volar forearm, wrist, or hand, with or without digital hypertrophy, followed by paresthesia (39%). A soft, mobile, nontender, nonfluctuant mass with variable degree of compressive median neuropathy is found on physical examination. Biopsy, which reveals abundant mature fat cells and fibrous connective tissue infiltrating between nerve fascicles and the space between the epineurium and the perineurium, is not necessary because the pathognomonic features of the mass on magnetic resonance imaging offer an accurate diagnosis. Treatment of nerve compression symptoms and macrodactyly should be addressed separately. Carpal tunnel release is the mainstay of treatment for neuropathy, and ray or digital amputation, wedge osteotomy, middle phalangectomy with arthroplasty, and epiphysiodesis are suggested options in the management of macrodactyly. Based on our review of the literature, we propose an algorithm for the diagnosis and treatment of LFH of the median nerve with or without macrodactyly.

RESECTION AND NERVE GRAFTING OF A LIPOFIBROHAMARTOMA OF THE MEDIAN NERVE

OBJECTIVE AND IMPORTANCE

Our patient's symptomatology, history, physical examination, diagnosis, management, and functional outcome 1 year after surgical repair is presented and discussed in light of the current literature on lipofibrohamartomas.

CLINICAL PRESENTATION

A 3-year-old boy presented to the Louisiana State University Nerve Clinic for evaluation and management because he was experiencing progressive symptoms of left hand swelling, dysesthesia, and impaired motor function. Physical examination demonstrated median nerve distribution motor impairment. Electromyographic/nerve conduction velocity studies also showed severely reduced conduction and amplitude of the median nerve response, and the magnetic resonance imaging findings were highly suggestive of lipofibrohamartoma. Hence, the presumed diagnosis was lipofibrohamartoma on the basis of imaging characteristics, location, and patient's age.

INTERVENTION

The patient was brought to the operating room with the objectives of carpal tunnel release and biopsy. However, routine intraoperative nerve action potential recordings showed no or very poor responses, consistent with significant loss of median nerve function. On the basis of the intraoperative nerve action potentials, we opted to resect the tumor back to healthy median nerve fascicles and to perform graft repairs. Surgery proceeded uneventfully, without any complications. Pathology confirmed the diagnosis of lipofibrohamartoma.

CONCLUSION

At 18 months postoperatively, the patient had excellent left hand function. On the basis of our experience with this patient, we believe that intraoperative nerve action potentials and the availability of usable proximal and distal nerve fascicles (which may be discernible on diagnostic imaging) are key factors in deciding whether a lipofibrohamartoma needs to be repaired or decompressed/biopsied. As illustrated by our case, we believe that resection and graft repair may be the best treatment option for some of these patients, and perhaps more so for pediatric patients.