An unusual case of solitary spinal intradural plasmacytoma: The unforeseen challenge

Localized proliferation of atypical plasma cells, either at bony or extramedullary, forms a rare subset of multiple myeloma (MM) disorders. The patients usually present with intractable pain and pathological fractures and respond well to radiotherapy. The clinical presentation is variable and radiologically is nonspecific. The spinal location is rare, and the solitary plasmacytoma in the intradural extramedullary (IDEM) region is unusual. Herein, we report the second case of solitary plasmacytoma at the lumbar IDEM region. A 54-year-male patient was referred to our institute with complaints of radicular pain in bilateral lower limbs along L5 dermatome for the past 3 months. The neurological examination was normal with power 5/5 and reflexes 2+, except for bilateral straight leg raising test restricted at 30. Magnetic resonance imaging of spine showed a well-defined eccentrically placed (left Side) spherical lesion at the level of L2 vertebrae. The lesion had foraminal extension and showed minimal contrast enhancement. The underlying ventral vertebral body was irregular and hyperosteotic. Our radiological impression was primarily neurofibroma, but the features were slightly atypical. The patient underwent L1-L2 laminectomy and excision of IDEM tumor. The histopathological features were consistent with plasmacytoma. The histopathology was a surprise to us. We further evaluated the patient for MM. He received adjuvant radiotherapy and is currently asymptomatic. An index of suspicion for SP must be kept among differentials of intradural lesions, especially when adjacent bony changes are present. The diagnosis of plasmacytoma warrants further workup according to the recommendations of the International Myeloma Working Group.