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|LETTER TO EDITOR
|Year : 2014 | Volume
| Issue : 5 | Page : 561-563
Renal small cell carcinoma presenting with solitary lumbar intradural metastasis
Anirudh Srinivasan1, Sivashanmugam Dhandapani1, Debajyoti Chatterjee2, Vijai Simha3
1 Department of Neurosurgery, Post Graduate Institute of Medical Education and Research, Chandigarh, India
2 Department of Pathology, Post Graduate Institute of Medical Education and Research, Chandigarh, India
3 Department of Radiotherapy, Post Graduate Institute of Medical Education and Research, Chandigarh, India
|Date of Submission||11-Sep-2014|
|Date of Decision||14-Sep-2014|
|Date of Acceptance||28-Sep-2014|
|Date of Web Publication||12-Nov-2014|
Department of Neurosurgery, Post Graduate Institute of Medical Education and Research, Chandigarh
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Srinivasan A, Dhandapani S, Chatterjee D, Simha V. Renal small cell carcinoma presenting with solitary lumbar intradural metastasis. Neurol India 2014;62:561-3
Primary neoplastic lesions constitute a small number of patients with cauda-equina syndrome.  Metastasis with cauda-equina syndrome is even rarer with only few cases reported in literature, mostly as a result of central nervous systemdrop metastases. This report presents a case of renal small cell carcinoma with solitary lumbar intradural metastases.
A 40-year-old male presented with progressive sensorimotor deficit in both lower limbs of six months duration and urinary incontinence. Neurologic examination revealed lower motor neuron paralysis of both lower limbs with sacral anesthesia and sphincter dysfunction. Magnetic resonance imaging of lumbosacral spine revealed contrast enhancing intradural space occupying lesion extending from L4 to S2 [Figure 1]. Patient underwent L4 to S1 laminectomy and subtotal excision of the tumor. Tumor adherent to the nerve roots was left behind. Histopathological examination of the tumor revealed tumor cells arranged in sheets, moderatelypleomorphic, negative for PAS with and without diastase and negative for CD 99, suggestive of metastatic small cell carcinoma [Figure 2] and [Figure 3]. Post operative PET-CT revealed a focus of intense FDG uptake in the lower pole of right kidney suggestive of primary malignant lesion [Figure 4]. Patient was given palliative radiotherapy andstarted on chemotherapy with cisplatin and irinotecan. There was gradual improvement in the power of lower limbs. However during the course of his second cycle of chemotherapy, he succumbed to his illness.
|Figure 1: Contrast MRI LS Spine showing homogenously enhancing intradural lesion extending from L4 to S2|
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|Figure 2: Synaptophysin immunohistochemistry showing strong cytoplasmic positivity in tumor cells|
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|Figure 4: Whole body PET CT showing evidence of abnormal metabolism in the lower pole of right kidney suggestive of primary|
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Spinal metastases are predominantly extradural and rarely breach the dura and may be the first manifestation of malignancy in ~20%, mostly representing tertiary spread from cerebral secondary sites.  It represents roughly 2-6% of all spinal metastases,  and can befound in 2% of cancer patients during autopsy.  In the majority the primary lesion in lung, followed by breast.  Intradural metastases are commonly thought tooriginate from cerebrospinal fluid (CSF) seeding. First, tumor cells are transferredto the brain (secondary drop metastasis), and then they enterthe CSF. This spreading causes either multifocal or diffuse infiltration of the leptomeninges and is known as leptomeningeal carcinomatosis. Finally, metastatic tumors arise in intradural extra-medullary (IDEM) lesions (tertiary drop metastasis). In the literature review, the development of IDEM metastasis was divided into earlier and later cases. The delayed metastasis may be related with tertiary dropmetastasis. However, early metastasis could not be explained by tertiary drop hypothesis. It may also be due to concurrent tumors from cell rests of neurulation. 
Primary renal small cell carcinomas are extremely rare with less than 30 cases reported in literature.  A review of patients with small cell carcinoma of the kidney revealed a median age at diagnosis of 62 years, women more commonly affected than men. The diagnosis of a small cell carcinoma, whether of pulmonary or extrapulmonary origin, can be established by light microscopic and immunohistochemical examination of tumor tissue. Extra pulmonary small cell carcinomas are invariably aggressive, with a tendency to develop early nodal and disseminated metastatic disease. Because of the unfavorable prognosis, multimodal therapy has been used increasingly to prolong life.  Chemotherapeutic regimens used in treating extrapulmonary small cell carcinomas are the same as those employed in small cell carcinomas of the lung. The severity of disease at diagnosis represents the most sensitive predictor of survival. 
Early diagnosis is important as it reducessurgical invasion and helps adequate recovery from neurological sequelae. Surgical treatment of metastatic cancer involvingintraduralcompartment is associated with highmorbidity and mortalityaccording to the primary lesion. Surgical intervention is appropriatewhen there is diagnostic uncertainty or for healthy patientswith good quality of survival or for patients with progressive neurological deficit.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]