#1: MP/H Rules
Source 1: 2014+ Grade Instructions
MP/H Rules/Histology/Grade--Unknown & ill-defined sites: What is the correct histology and grade of a liver biopsy with metastatic neuroendocrine carcinoma low to intermediate grade if primary site is unknown? See Discussion.
CT-guided liver biopsy, diagnosis: Metastatic neuroendocrine carcinoma. Diagnosis Comment: Cytology of the tumor appears to be low to intermediate grade.
Would this case be coded as an atypical carcinoid tumor (8249/3) based on SINQ 20170033 and the statement of intermediate grade; or should this be 8240/3 (neuroendocrine tumor) per SINQ 20160023 because it is a metastatic site? More clarification is needed on when to code 8249/3 or 8240/3 for a neuroendocrine carcinoma or neoplasm seen in a metastatic specimen only when there is specified grade.
Assign histology code 8246/3 and assign code 9 for grade.
Since the primary is unknown and the type of NEC is not definitively stated, code neuroendocrine carcinoma, NOS based on the diagnosis.
Code grade from primary tumor only. Assign grade code 9 when the primary site is unknown. See instruction 2.b. in the Grade Coding Instructions for 2014+.
SINQ 20170033 and SINQ 20160023 provide instructions for coding the grade/differentiation field. Using these SINQ questions to code histology could lead to errors.