Histology Coding Rules: Colon/Rectum
Use a mixed histology code if one exists
Use a combination code if one exists Example: Sigmoid lesion, adenocarcinoma with mucinous and clear cell differentiation
Mucinous adenocarcinoma 8480/3 Clear cell adenocarcinoma 8310/3
Answer: 8255/3 Adenocarcinoma with mixed subtypes
The next two rules pertain to mixed and combination codes.
Rule 3: Use a mixed histology code if one exists.
Rule 4: Use a combination code if one exists. When using a mixed or combination histology code, the word and or mixed will be in the diagnosis.
Example: The single lesion of the sigmoid is described as adenocarcinoma with mucinous and clear cell differentiation. The mucinous and clear cell differentiation are two different adenocarcinoma subtypes combined with adenocarcinoma. The histology is recorded as adenocarcinoma with mixed subtypes (8255/3).