#1: Solid Tumor Rules (2018)
#3: Brain and CNS
Source 1: 2018 Solid Tumor Rules
Notes: Malignant CNS; July 2019 Update
Solid Tumor Rules (2018)/Histology--Brain and CNS: How is the histology coded when the diagnosis comment for a posterior fossa tumor resection states: Taken together, these findings are indicative of medulloblastoma with extensive nodularity? See Discussion.
Example: Posterior fossa tumor resection final diagnosis was medulloblastoma, WHO Grade IV. The diagnosis comment notes the current tumor resection reveals large irregular reticulin-free nodules with streams of neoplastic cells in a fibrillary background in association with narrow reticulin-rich internodular strands of poorly differentiated neoplastic cells. Taken together, these findings are indicative of medulloblastoma with extensive nodularity. The diagnosis comment provided only one histology.
Per the 2018 Solid Tumor Manual, Malignant CNS, Priority Order for Using Documentation to Identify Histology instructions, an addendum or comment has priority over the final diagnosis. Although indicative is not listed on any ambiguous terminology list, is this an ambiguous diagnosis that must be ignored? Or does the diagnosis comment in this case provide a single, specific diagnosis of medulloblastoma with extensive nodularity?
Code as medulloblastoma, nodular (9471/3) based on the findings from both the comment and final diagnosis.