Intracranial oculomotor nerve rhabdomyoma

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.

Intracranial Rhabdomyoma: Case Report and Review of the Literature

A 24-year-old male presented with eight months of increasingly severe frontal headaches, decreased right facial sensation, and periodic vertigo. Magnetic resonance imaging demonstrated a heterogeneously contrast-enhancing mass involving and expanding the right foramen ovale.  A biopsy of the lesion was performed, and the final pathologic diagnosis revealed a neoplastic rhabdomyoma. To date, only five cases of intracranial rhabdomyoma have been reported, and a rhabdomyoma involving the trigeminal nerve has never been described in an adult. This manuscript reviews the available literature and highlights the clinical, imaging, pathologic characteristics, and surgical management of these exceedingly rare lesions.

A 68-year old man with a cerebellopontine angle tumor

We report on a 68-year-old male with a cerebellopontine angle tumor manifesting at the 8th cranial nerve and presenting histopathological features of a rhabdomyoma. A literature review revealed four reports of intracranial nerve rhabdomyoma, all of adult type and including one manifestation at the vestibular nerve. We present the first case of a fetal type extracardiac rhabdomyoma manifesting at a cranial nerve. Although rare, rhabdomyomas must be considered in the differential diagnosis of vestibular schwannomas.

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.

Undifferentiated sarcoma of the sellar region

Malignancies lacking specific features of cellular maturation are termed "undifferentiated" and represent 5-10% of all human tumors. They are encountered at a variety of sites but do not, as a rule, arise in the sellar region. A 39-year-old male with a history of testicular seminoma and an unsuccessful biopsy of a third ventricular neoplasm, presented with visual disturbances and memory loss. Light microscopically, the tumor consisted entirely of undifferentiated spindle cells. No germ cell component was noted. An exhaustive immunohistochemical study found immunoreactivity for vimentin and desmin, but for no other myoid markers. Polymerase chain reaction showed no X;18 translocation. Based upon these studies, a diagnosis of "undifferentiated sarcoma" was made. Our case, being highly unusual among reported sellar neoplasms, underscores the difficulties inherent in the differential diagnosis of undifferentiated neoplasms.

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.

An intrasellar rhabdomyosarcoma misdiagnosed as pituitary adenoma

BACKGROUND

Rhabdomyosarcoma is a malignant tumor of the skeletal muscle cells. Those tumors mainly affect children and arise in primitive fetal mesenchyme even at sites that do not contain skeletal muscle. However, very few intracranial rhabdomyosarcomas have been reported. No previous case of primary intrasellar rhabdomyosarcoma except for 1 case has been reported in the literature.

CASE DESCRIPTION

A 44-year-old woman presented with fatigue and diplopia associated with amenorrhea and galactorrhea. Visual field evaluation revealed a superior temporal deficit in both eyes. A right afferent pupillary defect was present. Magnetic resonance imaging revealed an intrasellar tumor with suprasellar extension. The tumor involved the sella turcica and right cavernous sinus. The patient was preoperatively diagnosed as pituitary adenoma, which was confirmed pathologically as rhabdomyosarcoma after the operation.

CONCLUSIONS

Our findings suggest that rhabdomyosarcoma should be considered in the differential diagnosis of a primary intrasellar neoplasm.

NEUROMUSCULAR CHORISTOMA OF THE OCULOMOTOR NERVE

OBJECTIVE

Neuromuscular choristomas (NMC) are rare benign tumors of the peripheral nerves. We report an NMC affecting the oculomotor nerve.

CLINICAL PRESENTATION

An 18-year-old girl presented with long-standing intermittent retro-orbital pain and oculomotor paresis. Magnetic resonance imaging scans demonstrated a small nodular lesion on the left oculomotor nerve, similar to the findings for a schwannoma.

INTERVENTION

The tumor was resected with the parental oculomotor nerve, which was reconstructed using a peroneal nerve graft. Postoperatively, the patient became pain-free, and her oculomotor function partially recovered. Histologically, the lesion consisted of well-differentiated smooth muscle fibers intermingled with mature nerve elements consistent with the diagnosis of an NMC, although the possibility of leiomyoma in this rare location was not excluded completely.

CONCLUSION

NMC may need histological confirmation for diagnosis if they occur in the intracranial space. The resection is feasible, and the function of the affected nerve can be at least partially restored with the nerve reconstruction.

Multifocal adult rhabdomyoma of the head and neck: a case report and literature review

Adult extracardiac rhabdomyomas are rare benign skeletal muscle tumors that most commonly present in the head and neck region. Only a few multifocal cases have been described to date in the world literature. We hereby present an additional multifocal case, the 14th worldwide, and review the literature.