Mesenchymal differentiation in trigeminal neurilemmoma

Reviewing Schwannoma-Hemangioma Composite Tumors With Their Tumorigenetic Molecular Pathways and Associated Syndromic Manifestations

Schwannomas are common peripheral nerve sheath tumors. Cavernous hemangiomas are vascular tumors that can affect any organ system. The coexistence of cavernous hemangioma with peripheral nervous system neoplasms is a rare occurrence. So far, 37 cases have been documented, and they have been divided into two categories: conjoined association (neoplasms discovered within the tumor tissue) and discrete association (neoplasms discovered outside the tumor tissue, thus placing neoplasms and tumors in close proximity but in different locations). Schwannomas and neurofibromas are the most prevalent tumors linked to cavernous hemangiomas that have been documented. The author provides a comprehensive review of all such cases published in the past with an emphasis on the implications of their tumorigenetic molecular pathways and syndromic manifestations.

Prevalence and clinicopathological characteristics of lipomatous neurofibromas in neurofibromatosis 1: An investigation of 229 cutaneous neurofibromas and a systematic review of the literature

BACKGROUND

Lipomatous neurofibroma (Lnf) is a histopathological variant with adipocytes noted among cells of cutaneous neurofibromas. We aimed to investigate the prevalence and clinicopathological features of Lnfs of neurofibromatosis 1 (NF1)-associated cutaneous neurofibromas and to review the literature systematically. We also evaluated the expression of leptin (a hormone involved in lipid metabolism) in neurofibromas to better understand the pathogenesis of Lnfs.

METHODS

A prospective histologic study was conducted on 229 cutaneous neurofibromas from 85 NF1 individuals. Leptin expression was immunohistochemically evaluated in 111 cutaneous neurofibromas. To systematically review the literature, two authors independently performed literature searches without year restriction.

RESULTS

Forty (17.5%) neurofibromas were lipomatous. Lnfs were significantly larger lesions and associated with females. Eighteen (7.9%) of all neurofibromas had multinucleated floret-like giant cells, and these were associated with Lnfs. All neurofibromas expressed leptin. We systematically reviewed 13 articles. Three large studies investigated Lnfs mainly in sporadic neurofibromas and suggested that 0.3% to 8.0% of tumors (NF1 and sporadic) are Lnfs.

CONCLUSION

In NF1, Lnfs are common, mainly in larger tumors and women. All cutaneous NF1-neurofibromas express leptin. It is unknown if the expression of leptin accounts for the lipomatous variant, but it may have a role in the pathogenesis of cutaneous neurofibroma.

Lipomatous Change in Uveal Melanoma: Histopathological, Immunohistochemical and Cytogenetic Analysis

PURPOSE

The aim of this study was to describe a case of lipomatous change in uveal melanoma.

PROCEDURES

The patient presented with a 2-year history of blurry vision. A full examination of the right eye revealed a dome-shaped pigmented subretinal mass in the choroid with a thickness of 9 mm and a diameter of 15 mm. The eye was enucleated and prepared for histopathologic, genetic and molecular investigation.

RESULTS

Histopathology revealed a small circumscribed area consisting of mature adipocytic appearing cells with abundant clear cytoplasm and small peripheral flattened nuclei within a spindle-cell melanoma of the uvea. The cytoplasm of the adipocytic cells stained negative for periodic acid-Schiff and Alcian blue and positive for Melan-A, HMB-45 and tyrosinase, confirming melanocytic lineage. Fluorescence in situ hybridization analysis confirmed trisomy of chromosome 6p22 and disomy of chromosome 3p13 in the nuclei of both the tumor spindle type B cells and in the nuclei of lipomatous tumor cells.

CONCLUSIONS

Lipomatous change can be added to the many histopathologic faces of uveal melanoma. To our knowledge, this is the first report of lipomatous change in uveal melanoma performed with cytogenetic investigations.

Development of intratumoral cyst or extratumoral arachnoid cyst in intracranial schwannomas following gamma knife radiosurgery

PURPOSE

Intracranial schwannomas presenting with cyst formation following gamma knife radiosurgery (GKRS) were investigated to clarify their clinicopathological characteristics.

METHODS

Between 1994 and 2006, 492 patients presenting with intracranial schwannomas underwent GKRS. Among them, seven cases demonstrated either new formation of cysts or enlargement of preexisting cysts, which were treated with microsurgical intervention. These cases were retrospectively reviewed with regard to neuroradiological findings and histopathology.

RESULTS

These seven cases included five vestibular and two trigeminal schwannomas. Preexisting cysts were enlarged following GKRS in three cases, while they were newly formed in four cases. Salvage microsurgery was carried out at 7-167 months after the GKRS, and subtotal resection was achieved in three, partial resection with or without cyst fenestration in four. Neurological symptoms were improved in all six symptomatic cases. Preoperative MRI demonstrated two characteristic types of cyst. One was the intratumoral type, indicating hemorrhagic change on the MRI. Histopathological analysis demonstrated a cavernous angioma within the solid compartment of tumor. These two cases demonstrated enlargement of residual tumor with new cyst formation after resection of only the cyst. The other type was extratumoral cyst, which had a structure with a thin cyst wall without contrast enhancement, and the cyst was composed of arachnoid cells without tumor cells. Extratumoral cysts enlarged despite effective control of the tumor itself, which may be caused by osmotic gradient induced by tumor degeneration following GKRS.

CONCLUSIONS

There were two types of cysts, intratumoral cyst and extratumoral arachnoid cyst, which developed following GKRS in intracranial schwannomas. Resection of the solid compartment as well as the cyst is required in schwannomas with expanding intratumoral cyst. Conversely, fenestration of the cyst alone might be effective in extratumoral arachnoid cysts.

Removal of cavernous malformation of the Meckel's cave by extradural pterional approach using Heros muscle dissection technique

BACKGROUND

We report on a patient with trigeminal neuralgia caused by an extraaxial cavernous malformation (CM) located within Meckel's cave. The lesion was removed via a pterional extradural approach with a modified temporalis muscle dissection technique, which was first described by Heros and Lee. Cadaveric dissections were performed to demonstrate the wider exposure gained by this approach.

METHODS

A 56-year-old man presented with a history of episodic shocklike, right-sided facial pain for 10 years. Neurologic examination revealed diminished sensation in the mandibular division of the right trigeminal nerve. Magnetic resonance imaging showed an ipsilateral enhancing lesion in Meckel's cave.

RESULTS

After placement of a lumbar drain, a right extradural pterional approach was undertaken. By reflecting the temporalis muscle posterolaterally, the craniotomy was extended so that the line of sight was level with the floor of the middle fossa. This allowed access to the lesion without needing to remove the zygoma. The lesion was resected with microsurgical technique. The patient's pain improved significantly after resection, and histopathologic examination confirmed the diagnosis of CM.

CONCLUSIONS

Extraaxial middle fossa CMs arising solely from Meckel's cave are rare. These lesions are safely and simply approached by posteriorly deflecting the temporalis muscle during a pterional craniotomy, avoiding excessive elevation of the anterior temporal lobe or further bony removal.

Cavernous malformation within a schwannoma: review of the literature and hypothesis of a common genetic etiology

The finding of cavernous malformations within tumors of the central or peripheral nervous system is a rare occurrence. We report a case of a histologically proven cavernous malformation found within an eighth cranial nerve schwannoma in a 76-year-old man. The patient presented with progressive loss of hearing on the left, facial pain and dysesthesia. Symptoms improved significantly after the tumor was subtotally resected through a left retrosigmoid craniotomy. Including the present report, 34 cases of cavernous malformations associated with tumors of nervous system origin, 24 cases (71%) involving tumors of Schwann cell origin, and 9 cases (26%) involving gliomas have been published. The cases were classified into two forms based on the type of association. Conjoined association, in which the cavernous malformation is located within the tissue of the nervous system tumor, and discrete association, in which the cavernous malformation and nervous system tumor are in separate locations. We explore the etiology of this association and hypothesize that a common genetic pathway may be involved in a majority of these cases.

Cutaneous lipomatous neurofibroma: characterization and frequency

BACKGROUND

There are numerous variants of cutaneous neurofibroma reflecting its manner of growth and histologic composition. Lipomatous neurofibroma is the latest described variant with only eight cases reported.

METHODS

A systematic study based on 320 consecutive specimens diagnosed of cutaneous neurofibroma was carried out. Conventional microscopy, immunohistochemistry, and statistical methods were used to determine the presence of fat cells, their amount, distribution, and frequency.

RESULTS

Intratumoral fat was observed in 22 (6.9%) neurofibromas. All these were dermal neurofibromas. Intraneoplastic fat was divided into two groups: focal and diffuse (regularly interspersed). Eighteen tumors (5.6%) presented adipocytes focally intermingled with the spindle cells. There were four (1.3%) neurofibromas showing spindle cell proliferation with regularly scattered adipocytes. Lipomatous neurofibroma was more frequent located on head and neck than non-lipomatous neurofibroma ( p = 0.04). Neurofibromas without mature adipocytes were more frequently immunoreactive for CD34 compared with tumors showing intratumoral fat ( p = 0.02).

CONCLUSIONS

We suggest that both metaplasia and aberrant adipose differentiation from multipotential cells may result in lipomatous neurofibroma. Focal presence of adipose cells may be attributable to metaplasia as the pathogenic mechanism. The fatty tissue being intrinsic to the tumor structure in its diffuse form, the lesion represents a distinctive tumor of the peripheral nerve sheath.

Schwannoma with rhabdomyoblastic differentiation: a unique variant of malignant triton tumor

A 54-year-old woman presented with intractable perianal, bilateral buttock, and radiating thigh/calf pain. An MRI scan showed an intradural, contrast-enhancing, ovoid mass in the cauda equina region at L1-L2. At laminectomy, the ovoid mass arose from a nerve root and, intact, was gross totally resected. Histologically, the dominant pattern was that of schwannoma. One year thereafter, the symptoms recurred. An MRI scan demonstrated an irregular, heterogeneously enhancing tumor recurrence. A repeat laminectomy disclosed a large fleshy tumor involving multiple nerve roots. The lesion was subtotally resected and showed pluridirectional differentiation toward embryonal rhabdomyosarcoma, primitive neuroectodermal tumor, and rare malignant epithelial cells. Review of the original tumor disclosed only foci of embryonal rhabdomyosarcoma and primitive neuroectodermal tumor. Based upon available data regarding divergent differentiation in peripheral nerve sheath tumors, this is a unique, previously undescribed tumor demonstrating rhabdomyosarcomatous, primitive neuroectodermal tumor and scant epithelial differentiation in a schwannoma. In essence, it is a variant of malignant Triton tumor because of its origin in a tumor consisting of well-differentiated Schwann cells. It supports the contention that the Schwann cell is the source of a variety of heterologous elements in nerve sheath tumors.

Cutaneous lipomatous neurofibroma

We report a cutaneous lipomatous neurofibroma on the skin of the left-side parietal area of approximately 9 months' duration in a 67-year-old woman. The regular distribution of adipose tissue throughout the lesion suggested that fat was an integral part of the tumor, not a metaplastic or degenerative process. To our knowledge, this type of lesion has not been documented. The main differential diagnosis embraces neurocristic cutaneous hamartoma, lipoma and its variants, cutaneous meningioma, and neural nevus with fat replacement. We propose that lipomatous neurofibroma of the skin is caused by aberrant development of adipose tissue in a neurofibroma. The lesion originated as pluripotential neural crest cells after migration. This acquired lesion could arise from local stem cells. The old suggestion that neuroectoderm is capable of mesenchymal differentiation may be relevant to the histogenesis of this neoplasm.

Ectomesenchymal hamartoma (benign "ectomesenchymoma") of the VIIIth nerve: case report

We report a previously undescribed hamartoma of the VIIIth nerve, consisting of adipose tissue, Schwann cells associated with myelinated nerve fibers, well-differentiated smooth and striated muscle fibers, and rare ganglion cells. The tumor was found in a 35-year-old Caucasian female who presented with right-sided hearing loss. The mass, which we designate an "ectomesenchymal" hamartoma, most likely developed from pluripotent neural crest cells ("ectomesenchyme"), which are capable of differentiating into a variety of neuroectodermal and mesenchymal cell types. The development of the neural crest, the concept of "ectomesenchyme," and the histogenesis of this tumor are reviewed.

Ossifying fibromyxoid tumour of soft parts: immunohistochemical and ultrastructural analysis

Ossifying fibromyxoid tumour of soft parts is a recently described benign neoplasm which usually presents in soft tissue. The histogenesis or pattern of differentiation is a source of controversy. Thirteen cases are reported herein. All arose in adults, principally on the upper trunk or head and neck region. None recurred. All but one tumour showed a shell of lamellar bone, laid down by reactive osteoblasts, at the tumour-host interface. The characteristic laciform, glomoid and fascicular patterns, usually in combination, necessitate differential diagnosis from chondroid, smooth muscle and neural tumours especially. Immunohistochemistry revealed positivity for S-100 protein in 10/12, desmin in 7/10 and smooth muscle actin in 4/8. Ultrastructural examination of four cases revealed prominent intermediate filaments, without myofilamentous organization, and a discontinuous external lamina. Immunoelectronmicroscopy localized desmin positivity to the filamentous meshwork. Differentiation therefore appears to take the form of an incomplete neural and smooth muscle phenotype, without evidence of complete maturation.

A combined neurilemmoma and angioma of the parasellar region. Case report

A combined neurilemmoma and angioma of the parasellar region is presented that clinically simulated a pituitary tumor. The lesion produced increased intracranial pressure and subarachnoid hemorrhage (SAH). This neoplasm is believed to have originated from the leptomeninges or the perivascular neural elements, or both. The angiomatous network within the tumor could have been the source of the SAH.