#1: Solid Tumor Rules (2018, 2021)
#3: Brain and CNS
Source 1: WHO Class CNS Tumors
Notes: 4th ed.
Source 2: 2018 Solid Tumor Rules
Notes: Non-Malignant CNS, July 2019 Update
Solid Tumor Rules (2018)/Histology--Brain and CNS: How are histology and primary site coded when a resection of a spine, designated intramedullary lesion, shows primary intramedullary melanocytoma? See Discussion.
Patient has a resection labeled as: Spine, designated intramedullary lesion. The Final Diagnosis is: Melanocytic neoplasm with features most consistent with primary intramedullary melanocytoma. The Diagnosis Comment states: The overall immunophenotypic and morphologic impression is a primary central nervous system melanocytoma.
The ICD-O-3 lists melanocytoma, NOS histology code as 8726/0, but does not provide a site-associated code. If the ICD-O-3 is used, the histology would be 8726/0 and the primary site presumably would be C720 since the tumor was specifically described as being intramedullary (i.e., within the spinal cord medulla).
Table 6 (Solid Tumor Rules, Non-Malignant CNS Equivalent Terms and Definitions) does not list either an intramedullary melanocytoma or melanocytoma (NOS). However, Table 6 does include meningeal melanocytosis 8728/0 and meningeal melanocytoma 8728/1. If Table 6 is used and the histology is coded 8728/1, then the primary site would presumably be C701 per the ICD-O-3 site-associated listing for this histology (C709).
Code primary site to spinal meninges (C701) and histology to meningeal melanocytoma (8728/1).
According to the WHO Classification of Tumors of the Central Nervous System, 4th ed., primary melanocytic neoplasms of the central nervous system are diffuse or localized tumors that presumably arise from leptomeningeal melanocytes. Benign or intermediate grade lesions are termed melanocytomas. Meningeal melanocytoma is defined as a well-differentiated, solid, and non-infiltrative melanocytic neoplasm that arises from leptomeningeal melanocytes. Most arise in the extramedullary, intradural compartment at the cervical and thoracic spine though they can be dural-based or associated with nerve roots or spinal foramina.