Does Prolonged Sitting Cause Tail Bone Tenderness And Pain?
could be pilonidal cyst
prolonged sitting may increase the risk for pilonidal cyst formation. This is actually an abscess and affects mostly men you sit for long periods (like drivers for example) and have a lot of hair on the area close to the tailbone.
Ask your doctor to have a look. If it is pilonidal cyst indeed then drainage might be needed.
Cancer related pain in this area would be very surprising!
perhaps a metastatic bone lesion
A metastatic bone lesion could cause pain on the tailbone but this would be a very unlikely (if possible) cause.
Rectal cancer usually presents with bleeding or constipation.
Let your doctor have a look at the area to check for skin lesions. If no lesion can be identified then an X-ray of the bones could help.