This data item is used to identify the type of multiple tumors in cases with multiple tumors that are abstracted and reported as a single primary using the SEER, IARC, or Canadian Cancer Registry multiple primary rules. Multiple tumors may individually exhibit in situ, invasive, or a combination of in situ and invasive behaviors. Multiple intracranial and central nervous system tumors may individually exhibit benign, borderline, malignant, or a combination of these behaviors. Multiple tumors found in the same organ or in a single primary site may occur at the time of initial diagnosis or later.

Patients with multiple tumors that are currently reported as a single primary may have a worse prognosis or more extensive treatment than patients with a single tumor. This data item will make it possible to identify important information about these cases for data analysis, and to compare individually reported cancer cases with historical data if the rules are changed.

Codes (refer to http://seer.cancer.gov/tools/mphrules/index.html for additional instructions).