#1: MP/H Rules
Source 1: 2007 MP/H Rules
MP/H Rules/Histology--Lung: What is the correct histology code for an initial biopsy of non-small cell carcinoma with neuroendocrine phenotype, possible large cell neuroendocrine carcinoma with a subsequent re-biopsy showing poorly differentiated small cell carcinoma after chemotherapy with no response? See discussion.
Patient had a biopsy in April 2014; pathology was reported as non-small cell carcinoma with neuroendocrine phenotype, possible large cell neuroendocrine carcinoma. The patient had five cycles of cisplatin/etoposide with no response. In May 2015, a re-biopsy at a referral institution reports poorly differentiated small cell carcinoma and states "feels that this could have been the histology all along and why patient has failed multi lines of chemo."
Code to 8041, small cell carcinoma, because the medical opinon confirms that this was the correct histology from the begining.
"Possible" is not an ambiguous term used to code histology. The MP/H rules do not include coding phenotype. That leaves non-small cell (8046/3) at time of diagnosis. Chemotherapy does not alter cell type so its likely the tumor was small cell all along only now proven with additional testing.
Page 14 of the SEER Coding Manual gives examples of when to change the abstract's original codes and here is one example: When better information is available later. Example 1: Consults from specialty labs, pathology report addendums or comments or other information have been added to the chart. Reports done during the diagnostic workup and placed on the chart after the registrar abstracted the information may contain valuable information. Whenever these later reports give better information about the histology, grade of tumor, primary site, etc., change the codes to reflect the better information.