Differential diagnosis A small<unk>  on the coccyx can be difficult to distinguish from a pilonidal<unk> . This is partly because both can be full of hair. A pilonidal<unk>  is a pilonidal sinus that is obstructed. Any teratoma near the body surface may develop a sinus or a fistula, or even a cluster of these. Such is the case of Canadian Football League linebacker Tyrone Jones, whose teratoma was discovered when he blew a tooth out of his nose.
Dermoid cyst
Teratoma
Epidermoid cyst
Branchial cleft cyst
Hidradenoma
Nabothian cyst
Papillary hidradenoma
Dentigerous cyst