Question: The physician documented a malignant neoplasm in the tuft of nerves at the terminal end of the patient's spinal cord. Which ICD-10 code should I choose? Ohio Subscriber Answer: In this case, you should choose C72.1 (Malignant neoplasm of cauda equina). Cauda equina is the bundle of spinal nerves and spinal nerve roots that originate in the tip of the spinal cord. This bundle consists of nerve pairs that originate from second lumbar level to fifth sacral level, and the coccygeal nerve. This bundle has both sensory and motor nerves and supplies the pelvic organs, perineum, and lower limbs. "Malignant tumors of the spinal cord and cauda equina are typically glioblastoma and malignant ependymoma respectively. Metastatic neoplasms can also be rarely seen," says Gregory Przybylski, MD, interim chairman of neurosurgery and neurology at the New Jersey Neuroscience Institute, JFK Medical Center in Edison. "Fortunately, most spinal cord neoplasms are benign, including astrocytoma and ependymoma."