Atypical benign melanotic thoracic intradural schwannoma Mohamed Mohamed, Spinos Panos, Atik Baborie, Kumar Das & Robin Pillay The Walton Centre for Neurology and Neurosurgery, Liverpool, Merseyside, UK negative) forming fascicles and streams (HE stain – Fig. 2A) with focal pericellular reticulin deposition (Fig. 2B). In areas reticulin surrounded small cell nests in places. Nuclei were oval or rounded with an occasional vacuolation. A few larger nuclei were present. Occasional proliferating nuclei were found (Ki67 stain) although difficult to identify given the abundance of pigmented cells. Hyalinised vessels were present. The tumour cells were melan-A positive (Fig. 2C), expressed S100 and focally GFAP. Invasive growth, nucleolar pleomorphism, increased mitosis or necrosis was absent. The appearances were those of a MS of a nonpsammomatous type. Following discussion at the Neuroscience multidisciplinary team meeting it was agreed that the patient would be followed up with interval MRI imaging. Following surgery the patients left lower limb power was unchanged, however, his power in his right leg had reduced to 3/5 throughout all muscle groups and he had developed urinary incontinence requiring catheterisation. The patient is currently undergoing rehabilitation at a dedicated neurological centre and 3 months after surgery his bladder function has improved and the catheter was removed. His right-leg function has improved (4⫹/5). On discharge he was mobilising with a walking aid.
Abstract We discuss the 8th known case of a patient who presented with an intradural intramedullary spinal melanocytic schwannoma. In this report we will discuss the hypothesis regarding the pathogenesis of the development of intradural schwannomas, the imaging modality of choice and treatment options. Keywords: intradural tumour; melanoma; radiology; schwannoma; spinal
Clinical details A 43-year-old Caucasian man presents with left-leg weakness that gradually got worse over a period of two years. The patient did not have any other neurological symptoms. On examination he had MRC grade power of 4/5 throughout all his lower limbs muscle groups in his left leg. In addition he had sustained clonus in his left ankle. The plantar reflexes were up going bilaterally with a sensory level of T11 to temperature and pain sensation. The neurological examination of his right leg, upper limbs and cranial nerves was unremarkable. Magnetic Resonance Imaging (MRI) of the spinal cord revealed a large (26 ⫻ 12 mm) contrast enhancing mass lesion occupying 90% of the spinal canal at the level of T9–T10 with the spinal cord displaced to the left (Fig. 1). Although metastasis was considered, the radiological and clinical findings were consistent with meningioma, ependymoma or lymphoma. However a dural based metastasis required excluding. A staging Computed Tomography (CT) scan was performed of the chest, abdomen and pelvis in addition to MRI of the brain and spine. No primary source of malignancy was discovered. A laminectomy was performed at the level of T9 and T10. Dark pigmentation was seen through the dura at this level. The dura was opened in the midline with careful removal of the intradural tumour with neurophysiological monitoring during surgery. A tumour of dark grey appearance was removed. Histology demonstrated a neoplasm composed of heavily pigmented spindle-shaped cells (Pearl’s stain
Discussion Schwannomas are benign, slow growing neoplasms composed of neoplastic Schwann cells. Melanocytic schwannoma (MS) is a rare variant of schwannoma composed of melanin-producing cells with ultrastructural features of Schwann cells. The most common sites are the posterior spinal nerve root, sympathetic chain, acoustic nerve, cerebellum and orbit. Intramedullary melanocytic schwannoma (IMS) is rare and this is the eighth reported case (Table I). Several theories have been put forward to explain the location of these tumours including the neoplastic extension of Schwann cells through the insertion site of the dorsal root, neoplastic differentiation of neuroectodermal cells in the pia to form IMS and the disordered migration of neural
Correspondence: Mohamed Mohamed, The Walton Centre for Neurology and Neurosurgery, Lower Ln, Liverpool, Merseyside L9 7LJ, UK. E-mail: [email protected] Received for publication 2 November 2013; accepted 22 November 2013
M. Mohamed et al.
Fig. 1. Figures show a homogenously enhancing mass (B) which appears to be intradural opposite the level of T9/T10. The high signal intensity on pre contrast T1 (A) and the low signal intensity on T2 sagittal (C) are due to the paramagnetic effect of the melanin. The lesion is inciting oedema within the underlying cord (C), which extended up to the level of T4 (not shown).
crest cells during neural tube closure.1 Other theories have tried to explain the melanocytic appearance of these tumours including the neoplastic differentiation of neural crest cells into Schwann cells with melanogenetic properties and the melanocytic transformation of previously normal Schwann cells.
IMS can be further subdivided into the psammomatous and non-psammomatous type depending on the microscopic presence of psammoma bodies. The psammomatous type which is associated with Carney complex involves skin pigmentary abnormalities, myxomas, endocrine tumours or overactivity, and schwannomas.2 Neurofibromatosis
Fig. 2. The figure showing the same locus in the tumour (IMS) with abundant pigmented spindle-shaped cells forming streams (A) with pericellular reticulin deposition of variable degree (B) and occasional small nests surrounded be reticulin. The cells express heavily melanin pigment (mel-A, C). The bar ⫽ 100 microns.
Atypical benign melanotic thoracic intramedullary tumour 413 Table I. Summary of reported cases. Demographics
Level of tumour
Male, 69 years old Female, 72 years old Female, 63 years old Female, 44 years old Male, 35 years old
Caudal medulla and C3 C4 and C6 C7 and T1 T2 and T3 C4 and C5
Not recorded Functional recovery Not recorded Partial neurological recovery Partial neurological recovery
Female, 56 years old Female, 62 years old
Conus medullaris T11
Gross total resection Partial resection Fine needle aspiration for diagnosis Gross total resection Gross total resection followed by further surgery 4 years later plus chemotherapy and radiotherapy Gross total resection Gross total resection
Current case: Male, 43 years old
T9 to T10
Gross total resection
(NF) type 2 is an autosomal dominant condition that is characterised by widespread dissemination of neurofibromas and shwannomas including the in central nervous system. However, our patient did not have any family history of NF and clinical and imaging examination did not demonstrate any other neurofibromas. Distinguishing between MS and malignant melanoma is of paramount importance in planning of management. Schwannomas and IMS show pericellular reticulin deposition and thus they are able to be distinguished from malignant melanomas histologically. From the limited number of documented cases it is noted that the treatment of IMS is gross surgical resection. Due to the rarity of these tumours the role of radiotherapy has not been established. However, there is a documented case of a patient with IMS who received postoperative radiotherapy for recurrence of tumour despite initial gross surgical resection. MRI is the preferred method for evaluating lesions of the spine cord. Melanin and, hence, MS, would be expected to have shortened T1 and T2 relaxation times leading to them appearing T1-hyperintense and T2–hypointense.3 On post contrast would expect homogeneous enhancement but it may be heterogeneous in the presence of haemorrhage within the lesion. Standard schwannoma would be typically be T1 iso/hypointense and T2 hyperintense. Standard schwannoma would typically demonstrate homogeneous enhancement and typically no evidence of haemorrhage. Gross total resection is the neurosurgical treatment for IMS since recurrence and malignancy are possibilities. This
Partial neurological recovery Good neurological recovery, no recurrence at 10 months Good neurological recovery, no recurrence at 6 months
treatment differs considerably if the diagnosis is metastatic melanoma as this has a median survival of 113 days if there is central nervous system involvement therefore surgery is not commonly advocated. Annual follow-up of patients with IMS with serial MRI imaging is necessary as recurrence of these tumours has been reported. If recurrence occurs a trial of radiotherapy and chemotherapy may be indicated although due to the rarity of this tumour no evidence is available to support this. The differential diagnosis for IMS is metastasis of a malignant melanoma and thus the patient requires a full body examination for any suspicious lesions and if found appropriate referral to dermatology should be made. Although rare IMS needs to be considered in all intramedullary lesions and appropriate imaging with MRI conducted in the attempt to diagnose the lesion prior to surgery. Declaration of interest: The authors report no declarations of interest. The authors alone are responsible for the content and writing of the paper.
References 1. Santaguida C, Sabbagh AJ, Guiot MC, Del Maestro RF. Aggressive intramedullary melanotic schwannoma: case report. Neurosurgery 2004;55:1430–4. 2. Hoover JM, Kumar R, Bledsoe JM, et al. Intramedullary melanotic schwannoma. Rare Tumours 2012;4:e3. 3. Smith AB, Rushing EJ, Smirniotopoulos JG. Pigmented lesions of the central nervous systems: radiologic-pathologic correlation. Radiographics 2009;29:1503–24.
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