There is a nice article in the journal Archives of Otolaryngology-- Head Neck Surgery (first reference below) which examines the relationship of preauricular sinuses to auricular cartilage.
The article takes you through a review of the embryology and then takes you through surgical treatmentWhile both cutaneous opening and fistulous tracts are classically located anterior to the external auditory canal, a reported variant form has its opening behind an imaginary vertical line drawn at the posterior most aspect of the tragus and the posterior aspect of the ascending limb of the helix. This variant typically presents with postauricular swelling and requires both postauricular and preauricular incisions for its removal.
There conclusionsClassically, the surgical approach consists of a simple sinectomy with an elliptical island of skin removed around the opening of the sinus and excision of the epithelial sinus tract. Various authors have advocated the use of either methylene blue or gentle probing of the tract to carefully delineate the tract. However, neither approach guarantees full removal of the tracts: reported recurrence rates are quite high, typically near 20%…………..
Because the present study is not a randomized controlled trial, our findings cannot be used to determine whether excision of cartilage or perichondrium prevents recurrence of preauricular sinuses. …… In over 50% of the specimens reviewed, the sinocartilaginous distance was less than 0.5 mm, and in nearly all of these cases, the epithelial tract was in continuity with stromal tissue histologically indistinguishable from the perichondrium.The removal of a small piece of cartilage or perichondrium does not produce a visible cosmetic deformity or add any significant morbidity. Therefore, the routine removal of a small portion of perichondrium and/or auricular cartilage along with the sinus tract may yield a more thorough excision and help to prevent recurrence.