Discussion

Lymphomas are malignant tumors arising from lymphoid tissue. It can be Hodgkin’s or non-Hodgkin’s type, later being more common, and their primary epidural occurrence is very rare.4 Out of all the primary central nervous system (CNS) tumors (which also includes spinal lymphomas), primary DLBCL of the CNS constitutes only 0.5% cases, occurring in approximately 2 cases per 10 million people. Spinal cord location is particularly rare.6
The pathogenesis of primary central nervous system lymphomas (PCNSLs) has been a matter of considerable debate among experts. Some authors mention that PCNSL arise de novo in nervous system tissues due to the presence of lymphoid precursor cells in this location.7,8 Others argue that tumors from local and distant sites spread in the epidural space resulting in their apparent primary presentation.9 The remaining, believe that an unrecognized preexisting retroperitoneal disease may exist before they present as PSEL.10
There is a male preponderance (69% vs 31%) of PSEL matching exactly with our case.11 Though the usual age of presentation is beyond 40 years of age, several cases have been reported in younger patients. Nambiar et al12 reported a case of primary thoracic (T5-T10) spinal epidural B-lymphoblastic lymphoma in a 19-year-old male from India. There are very few reported cases of spinal epidural NHL in younger age groups.13 Our case of a 24-year-old male is another addition to it.
The thoracic spine is the most commonly involved site followed by the lumbosacral and cervical spine.8 The common occurrence of PSEL in the thoracic spine can be explained by the rich venous plexus in this site, greater length of the thoracic spine as compared with cervical and lumbar, more tolerance for bulky disease in the thorax and abdomen and the existence of unrecognized preexisting retroperitoneal disease.10, 14 The usual location of the tumor in spinal epidural space is usually dorsal.15 Our case too had a similar finding of lesion present dorsally and located at the thoracolumbar region.
The onset of symptoms is usually subacute, occurring over a few days to weeks. The symptoms and signs of the disease depend on the location and size of the tumor. Localized back pain followed by lower limb weakness is the most common symptom.11 Local back pain, sometimes accompanied by radicular pain to legs and abdomen can be the prodromal symptom that can persist for several months to a year. Then, the phase of rapid neurological deterioration occurs over 2-8 weeks which is due to spinal cord compression.14 Bladder and bowel disturbances appear only later in the course.16It may give us the idea of time since the onset of the pathology. The presenting features in our case were back pain radiating to bilateral lower limbs for three months followed by neurological deficits for the last 12 days without bladder involvement.
B symptoms (fever, night sweats, and weight loss) were found to be rare and none had hepatomegaly or splenomegaly in one of the largest surveys, which is consistent with our case too. As most of the patients presented in the earlier stage, B symptoms were probably absent.11
MRI is the investigation of choice in the preoperative and postoperative evaluations.10 PSEL appears in MRI as isointense on T1W image and iso- to hyperintense on T2W image, with marked contrast enhancement.15 Contrast enhancement with Gadolinium further helps in the assessment of extraosseous soft tissue components. This allows a better differentiation of various pathologies (e.g., metastatic carcinoma and sarcoma), tumor extent, and bony involvement.15 Similar features were recognized in our case too.
The whole-body scan should be performed to identify lungs, pleural, splenic, gastric, intestinal, pancreatic, and renal involvement. Bone marrow biopsy from the sternum or iliac crest is required to rule out lymphoreticular involvement. CBC, LDH, and chest X-ray should be performed as well. In our case, we could not find any positive reports. Lumbar puncture is not recommended because it is potentially hazardous because of the coning phenomenon and it is also of limited diagnostic value as it shows a non-specific increase in protein levels; neoplastic cells are rarely found.17,18
Monnard et al11 have recommended surgical decompression in the form of partial or total removal of the tumor mass and/or decompressive laminectomy. Doing so relieves the spinal cord compression and also establishes the correct histological diagnosis. Surgery is clearly indicated when the diagnosis is not yet established.1 Emergency decompression is needed only in cases of acute paresis and/or loss of bowel/bladder control.16 Functional recovery of patients suffering spinal cord compression due to PSEL is relatively better than that of patients with metastatic carcinoma.4
Histopathological examination of the biopsy specimen usually shows diffuse proliferation of atypical lymphoid cells,8which is similar to our finding. Immunohistochemistry analysis with positive CD20+, CD10+, BCL6+, and MUM-1- further supported our diagnosis of DLBCL (germinal center type).5, 19Positive Ki-67 suggested the aggressiveness of the tumor.
Combined modality treatment including radiotherapy and chemotherapy has been recommended to be the most efficient treatment because lymphomas are very chemo- and radiosensitive tumors.11, 18, 20In the largest survey until now, local control of 88% and 5-year overall survival of 69% have been observed with combined modality treatment.11 Earlier diagnosis and treatment is associated with improved functional outcomes. Several authors report that patients with more aggressive histological tumor types have a poorer prognosis. Patients of over 40 years of age with aggressive histological tumors have a poor prognosis.10 Our case was a 24-year-old male, otherwise healthy, and was diagnosed early and underwent surgery with significant neurological improvement, which is the most favorable prognostic indicator of overall survival.11 He responded well to chemotherapy with complete neurological recovery.