What is the Difference Between Synchronous and Metachronous?

The terms "synchronous" and "metachronous" refer to the timing of the occurrence of multiple primary malignancies in the same patient. The difference between the two lies in the time lag between the development of the first and second malignant transformations:

• Synchronous: Two or more primary carcinomas coexist at the time of diagnosis or are detected within a 2-month period postoperatively. The Surveillance Epidemiology and End Results Program (SEER) defines synchronous multiple primary cancers as those diagnosed within a 2-month period.
• Metachronous: Metachronous tumors refer to the second primary cancer being diagnosed more than 6 months after the primary cancer. These tumors may be detected 6 months to several years after the resection of the first primary.

In summary, synchronous and metachronous malignancies differ in the time lag between the development of the first and second primary cancers. Synchronous tumors are diagnosed within 2 months or coexist at the time of diagnosis, while metachronous tumors are diagnosed more than 6 months after the primary cancer.

Comparative Table: Synchronous vs Metachronous

The key difference between synchronous and metachronous cancers is based on the onset of the second primary cancer. Here is a table summarizing the differences between synchronous and metachronous carcinomas:

Both synchronous and metachronous carcinomas lead to the metastasis of cancer and are more prevalent in colorectal cancers. The diagnosis of both types of carcinomas takes place via biopsies and scopy tests. Genetics plays an important role in synchronous and metachronous carcinoma development.