Benign triton tumor of the trigeminal nerve

Pediatric benign triton tumor of trigeminal nerve: a case report and literature review

PURPOSE

Benign triton tumors (BTTs) in the pediatric population are extremely rare occurrences. Paucity of data on BTTs poses both diagnostic and therapeutic challenges, particularly when found intracranially.

METHODS

A case report of a 10-year-old male diagnosed with incidental maxillary trigeminal (V2) BTT is presented. We discuss radiographic and histopathological interpretations. Furthermore, we provide a brief review of current literature and historical background on pediatric trigeminal BTT diagnosis, histopathology, and management.

RESULTS

Successful gross total resection of the tumor was achieved via Dolenc approach to the cavernous sinus. Management options with consideration of outcomes from the few prior cases reported in the literature are presented.

CONCLUSION

Treatment of trigeminal nerve tumors requires a broad differential diagnosis and understanding rare tumors is essential in the diagnosis and treatment algorithm.

Orbital neuromuscular choristoma of the ophthalmic nerve

INTRODUCTION

Neuromuscular choristoma (NC) is a rare tumor composed of striated muscle fibers admixed with nerve fibers that often affects large peripheral nerve trunks in children. To the best of our knowledge, this is the first reported case in the literature of a NC of the ophthalmic nerve in an adult.

CASE DESCRIPTION

A 27-year-old woman presented with a 20-day history of left periorbital headache radiating to the frontotemporal region, with associated tearing, nausea, and vomiting. The examination was normal, except for hypoesthesia in the distribution of the first trigeminal nerve branch (V1). Cranial computerized tomography showed a lesion in the left orbit and cavernous sinus with widening of the superior orbital fissure. On magnetic resonance imaging, the lesion was well-defined with fusiform morphology and showed a central cystic component and peripheral enhancement. An extradural approach was performed with subtotal tumor resection. Biopsy showed proliferation of striated muscle cells admixed with nerve fascicles and Schwann cells. A pathological diagnosis of NC of V1 was determined. Six months after surgery, left hypotropia with limitation of supraduction was observed, as well as hypoesthesia and paralysis of the left forehead with ipsilateral eyebrow ptosis. The rest of the examination remained within normal limits.

CONCLUSION

NC should be considered in the differential diagnosis of a young patient with periorbital headache and hypoesthesia in the V1 region.

Incidental Hamartoma in an elderly patient: a case report

Background

Neuromuscular hamartoma is a very rare tumor; with only five cases reported in the orbit. It often occurs in infants and young children and involves large peripheral nerves, but there has been only few reports of occurrence in the orbit and adults.

Case presentation

This paper describes a 70-year-old man with an incidental orbital mass detected by an imaging test and who later developed associated symptoms. The mass was diagnosed as neuromuscular hamartoma. Superior rectus muscle recession and inferior rectus muscle resection were performed in the right eye for hypertropia secondary to postoperative inferior rectus muscle palsy. Hypertropia in the right eye and diplopia improved after surgery, and regular follow-up is underway.

Conclusion

This is the first case of an incidentally detected orbital mass diagnosed by histologic examination as a neuromuscular hamartoma in an older patient whose proptosis progressed after a long period of inactivity.

Hamartomas of skin and soft tissue

Hamartomas are benign lesions composed of aberrant disorganized growth of mature tissues. Choristomas are similar, except that they are composed of tissues not normally found at the anatomic site in which the lesion is arising. A wide range of hamartomas and choristomas can arise in the skin and soft tissue. Some of these may cause diagnostic difficulty and potentially be mistaken for neoplasms. Some neoplasms may resemble hamaratomas. Here we review the current clinical and pathologic features of these lesions, both common and rare, and discuss how to distinguish them from other entities in the differential diagnosis.

Benign triton tumor: multidisciplinary approach to diagnosis and treatment

Benign Triton tumor (neuromuscular choristoma) is a rare mass that most commonly occurs as a multinodular expansion of tissue in or around large nerves. Intracranial occurrence is uncommon. We report on a 4-year-old girl presenting with a right-sided facial mass and trismus. Imaging revealed a large, complex mass extending from the ventral aspect of the pons, along the trigeminal nerve, through the foramen ovale, and into the right infratemporal fossa. The lesion was partially enhancing, invaded adjacent infratemporal musculature, was associated with marked overgrowth of the right coronoid process, and induced bony erosion of the middle cranial fossa. After needle biopsy, a multidisciplinary team, including plastic surgery, otolaryngology, and neurosurgery, performed a combined, multistep, single-day surgical approach for resection. Unique to this case was the resection of the coronoid process, a modified middle fossa intradural and extradural approach, coupled with a transfacial infratemporal approach. Microscopically, the resected tissue showed skeletal muscle, fibrous tissue, and nerve in a disorganized arrangement characteristic of a benign Triton tumor. We present this case to illustrate diagnostic clues and pitfalls in the preoperative evaluation of a benign Triton tumor. We also highlight the pathologist's role as a partner in a multidisciplinary approach to diagnosis and treatment of this rare pediatric mass, potentially the largest Triton tumor in the head reported to date.

Adulthood benign triton tumor developed in the orbit

Benign triton tumor (BTT) or neuromuscular hamartoma is an uncommon tumor composed of mature neural and well-differentiated striated muscular elements. Its development is exceptionally rare in the adult and head region. This report describes a case of adulthood BTT that occurred in the orbit. The patient was a 53-year-old woman who presented with right periorbital swelling and pain in eyeball over 2 months. Magnetic resonance imaging revealed a well-enhancing mass surrounding optic nerve and ocular muscles in the right retrobulbar area. The tumor was subtotally removed via transcranial approach. Its pathological diagnosis was confirmed to be a neuromuscular hamartoma. She developed diplopia postoperatively. Adulthood BTT should be considered in the differential diagnosis of head and neck tumors. It is also important to make adequate therapeutic strategy to avoid postoperative neural dysfunction.

Neuromuscular choristoma: characteristic magnetic resonance imaging findings and association with post-biopsy fibromatosis

OBJECTIVE

To describe imaging characteristics of neuromuscular choristomas (NMC) and to differentiate them from fibrolipomatous hamartomas (FLH).

MATERIALS AND METHODS

Clinical and imaging characteristics of six patients with biopsy-proven NMC and six patients with FLH were reviewed by musculoskeletal, a pediatric, and two in-training radiologists with a literature review to define typical magnetic resonance imaging features by consensus. Five radiology trainees blinded to cases and naive to the diagnosis of NMC and a musculoskeletal-trained radiologist rated each lesion as having more than or less than 50% intralesional fat, as well as an overall impression using axial T1 images. Sensitivity, specificity, accuracy, and interobserver agreement kappa were determined.

RESULTS

Typical features of NMC include smoothly tapering, fusiform enlargement of the sciatic nerve or brachial plexus elements with T1 and T2 signal characteristics closely following those of muscle. Longitudinal bands of intervening low T1 and T2 signal were often present and likely corresponded to fibrous tissue by pathology. Four of five patients with long-term follow-up (80%) developed aggressive fibromatosis after percutaneous or surgical biopsy. Nerve fascicle thickening often resulted in a "coaxial cable" appearance similar to classic FLH, however, using a cutoff of <50% intralesional fat allowed for differentiation with 100% sensitivity by all reviewers and 100% specificity when all imaging features were utilized for impressions. Agreement was excellent with all differentiating methods (kappa 0.861-1.0).

CONCLUSIONS

NMC can be confidently differentiated from FLH and malignancies using characteristic imaging and clinical features. When a diagnosis is made, biopsy should be avoided given frequent complication by aggressive fibromatosis.

Fibromatosis arising in association with neuromuscular hamartoma of the mandible

Aggressive fibromatosis is a benign but locally-aggressive tumor, which most often affects the muscles of the shoulder, the pelvic girdle, and the thigh. It usually affects adolescents and young adults. Desmoplastic fibroma, considered the bone counterpart of soft tissue fibromatosis, is a rare tumor that usually affects the metaphyseal or diaphyseal portions of long bones or, less commonly, the jaw. Neuromuscular hamartoma, a rare developmental lesion composed of mature elements of both striated muscle and nerve, is usually diagnosed in infants and children and affects large nerve trunks. Rarely, it can affect the head and neck region. Occasional cases showing an association between aggressive fibromatosis and neuromuscular hamartoma have been reported in the literature. Here we present a unique case of an adult patient with desmoplastic fibroma of the mandible in association with neuromuscular hamartoma.

Neurogenic tumors of soft tissue

Neurogenic tumors are an uncommon yet important category of soft tissue tumors in children and adolescents because of their frequent association with various genetic syndromes. The heterogeneous cellular composition of the peripheral nerve and the wide metaplastic capacity of the neural crest and its derivatives generate a variety of neoplasms with neurogenic differentiation. This article reviews the clinicopathologic features and differential diagnosis of neurogenic tumors in the first two decades of life, and highlights use of selected ancillary methods for diagnosis.

Fibromatosis: a potential sequela of neuromuscular choristoma

OBJECT

Neuromuscular choristoma (NMC) is a rare peripheral nerve lesion in which mature skeletal muscle fibers lie within the nerve and its fascicles. Given limited follow-up, its natural history is poorly understood. The occurrence of aggressive fibromatosis in one of the authors' patients and its occurrence in reported cases suggests an etiological relationship between the 2 lesions. This study attempts to explain the association and its frequency.

METHODS

All cases of NMCs seen in consultation or treated at the Mayo Clinic were identified. Demographic and clinical data were reviewed in cases with coexistent aggressive fibromatosis. Pathology and neuroimaging studies were reexamined. In addition, an extensive literature review was performed to explore the association of NMC with aggressive fibromatosis, with special attention given to pathological and imaging characteristics and the development of aggressive fibromatosis.

RESULTS

The authors identified 10 patients with a diagnosis of NMC who were treated at the Mayo Clinic between 1992 and 2010. Four of 5 with adequate follow-up had developed a definite or suspected aggressive fibromatosis. A review of the initial pathological specimens in these cases revealed no evidence of fibromatosis, but all of the lesions exhibited accompanying hypocellular collagenous tissue. On MR images, all cases showed areas of low signal intensity, which significantly differed from muscle, nerve, and NMC components. On available serial MR imaging studies, aggressive fibromatosis seemed to originate in such lower-intensity regions. In the 18 previously reported cases of NMC, 5 patients developed recurrent masses diagnosed as either definite (2 cases) or possible (3 cases) fibromatosis. Review of the published imaging studies in these cases suggests the presence of lower intensity areas similar to those observed in the 10 patients treated at the Mayo Clinic.

CONCLUSIONS

This study confirms that the development of aggressive fibromatosis in patients with NMC has been underreported. A direct relationship between the NMC and the development of aggressive fibromatosis is suggested by pathological and neuroimaging evidence.

Intraocular Neuromuscular Choristoma

BACKGROUND AND IMPORTANCE:

Neuromuscular choristomas (NMCs) are rare benign tumors of the peripheral nerves. Although histopathological characteristics of this unusual lesion have been recognized, in this regard, neuroimaging findings have not been well described previously. We report the first intraconally located NMC affecting the oculomotor nerve, with histopathological and radiological characteristics.

CLINICAL PRESENTATION:

A 10-year-old girl presented with sudden-onset left temporal and retro-orbital pain. Magnetic resonance imaging scans demonstrated a small, capsulated, retro-orbital, intraconal solid lesion that was diagnosed as an atypical dermoid cyst preoperatively. The tumor was resected subtotally. Postoperatively, the patient became pain free, but ipsilateral ptosis and upward eye movement failure developed. Histologically, the lesion consisted of well-differentiated striated muscle fibers intermingled with mature nerve elements consistent with the NMC.

CONCLUSION:

Although intracranial NMCs need histological confirmation for diagnosis, neuroimaging might contribute to the preoperative diagnosis and management strategy of treatment. We report the first intraconal NMC, which should be considered in the differential diagnosis of intraorbital tumors.

Classification of Neural Tumors in Laboratory Rodents, Emphasizing the Rat

Neoplasms of the nervous system, whether spontaneous or induced, are infrequent in laboratory rodents and very rare in other laboratory animal species. The morphology of neural tumors depends on the intrinsic functions and properties of the cell type, the interactions between the neoplasm and surrounding normal tissue, and regressive changes. The incidence of neural neoplasms varies with sex, location, and age of tumor onset. Although the onset of spontaneous tumor development cannot be established in routine oncogenicity studies, calculations using the time of diagnosis (day of death) have revealed significant differences in tumor biology among different rat strains. In the central nervous system, granular cell tumors (a meningioma variant), followed by glial tumors, are the most common neoplasms in rats, whereas glial cell tumors are observed most frequently in mice. Central nervous system tumors usually affect the brain rather than the spinal cord. Other than adrenal gland pheochromocytomas, the most common neoplasms of the peripheral nervous system are schwannomas. Neural tumors may develop in the central nervous system and peripheral nervous system from other cell lineages (including extraneural elements like adipose tissue and lymphocytes), but such lesions are very rare in laboratory animals.

Neuromuscular hamartoma of the trigeminal nerve in an adult

A 36-year-old female presented with a long-standing history of headache. Computed tomography scan and magnetic resonance imaging revealed an enhancing lesion occupying the right Meckel's cave, enlarging the trigeminal ganglion and extending through the foramen ovale into the infratemporal fossa. A right frontotemporal extradural approach to the cavernous sinus was performed and a firm, pinkish lesion intermingled with nerve fibers enlarging the trigeminal ganglion and V3 branch was identified. Frozen section was suggestive of a neuromuscular hamartoma. The lesion was sub-totally resected to avoid injury to the motor branch. Neuromuscular hamartoma should be included in the differential diagnosis of cavernous sinus and cranial nerve lesions in adults.