Histology Coding Rules: Colon/Rectum
Multiple Tumors in Same Organ Reported as Single Primary
1. Code histology when multiple tumors have same histology
Example: Well differentiated adenocarcinoma of rectum; separate metastatic tumor island, adenocarcinoma, with irregular contours present in fat
Answer: 8140/31 Adenocarcinoma
The rules for multiple tumors in the same organ reported as a single primary follow.
Rule 1: Code the histology when multiple tumors have the same histology.
Example: There is a tumor in the rectum with adenocarcinoma as well as a separate metastatic tumor island in the fat with adenocarcinoma. Because the tumor island in the fat has irregular contours, it is considered a metastatic nodule and not lymph node metastasis. This is a single primary, and the histology is recorded as adenocarcinoma (8140/3).