The October 2022 CTR Coding Break titled Malignant Cranial & Peripheral Nerve Tumors reviews anatomy of the twelve cranial nerves and peripheral nerve system, Table 4 in the Solid Tumor Rules Malignant CNS and Peripheral Nerves chapter, as well as discusses a couple case examples. Cranial Nerves come straight out of the brain and when those cranial nerves exit the cranium, they become peripheral nerves. Cranial nerves transfer information between the brain and parts of the human body and are named in roman numerals according to their structure or function. There are 2 main types in the peripheral nerve system called autonomic and somatic. Autonomic system is where the brain runs automatically and without thinking. Somatic systems are functions you manage by thinking about them. Solid Tumor Rules Manual, chapter on malignant CNS & peripheral nerves has a table 4 called coding primary site for malignant tumors of cranial and peripheral nerves. This table helps to determine whether a malignant cranial nerve tumor should be coded to a cranial nerve or to a peripheral nerve. The anatomic location of the tumor determines whether the primary site is a peripheral or cranial nerve. Two case examples are included.