Thank you for your query at DoctorSpring.com.
I do understand that it can be quite distressing dealing with issues of the colon with a family history of colon cancer. However, there is no need to panic.
Honestly, your question is very confusing.
You have told that a single polyp at sigmoid colon was found, which was removed and that was benign.
"Polyp" is a colonoscopic/macroscopic description and "adenoma" is microscopic description. Both mean the same. A polyp is basically an adenoma.
Benign polyp means an adenoma, not cancer. If that polyp was removed, it means the adenoma was removed.
However, if that polyp was not removed completely, which could be one possibility in your case, then repeat resection can be done after 4 weeks interval. There is no need to hurry here as something benign will not turn malignant (cancerous) in such a short period. There is definitely no need to panic. You need not wait for three months to get the repeat colonoscopy.
In all probability, your polyp might have been removed completely and your doctor just wants to re-examine the site of the polyp after 3 months, to check for recurrence. This is the second possibility. In either case, you do not have anything to worry about.
Please do get regular colonoscopic examinations done, as you have a family history of colon cancer.
I hope this was helpful. Feel free to ask queries.
Wish you a good health.