Neurology & Pain Management Coding Alert

Question: What is the difference between a schwannoma and neurofibroma?

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Answer: Both terms refer to the two most common and typically benign nerve tumors. Both schwannomas and neurofibromas originate in the insulating covering of peripheral nerves called the nerve sheath. There is often confusion between the two tumors and sometimes a distinction can only be made by a pathologist with microscopic examination as the two tumors arise from different nerve cells.

Schwannomas characteristically stay on the outside of the nerve but may push it aside or against a bony structure causing damage. Neurofibromas, in contrast, typically infiltrate the nerve and splay apart the individual nerve fibers. Unlike schwannomas, which are easily separated  from the host nerve with surgery, neurofibromas are more difficult to excise.

Neurofibromas are often associated with neurofibromatosis (237.7x), but the tumors also occur in patients without the condition. It's often difficult to distinguish these tumors with pre-operative radiologic studies, so your neurologist probably won't know the diagnosis conclusively until the final pathology report is available.

Pinpoint diagnosis: Under the individual listings for both of these nerve tumors, the ICD-9 Alphabetic Index directs coders to "see also Neoplasm, connective tissue, benign." When choosing your diagnosis, rely on the "connective tissue" choices in the Neoplasm Index. Code according to the tumor's location and status (malignant, benign, etc.). The Neoplasm Table in the ICD-9 Alphabetic Index includes a comprehensive list of potential diagnosis codes for schwannomas and neurofibromas based on anatomic location of the tumor. For sites that do not appear on the list, guidelines direct you to code to the neoplasm of that site --  such as 215.4 (Other benign neoplasm of connective and other soft tissue; thorax) for a neurofibroma of the chest wall.