High-Resolution Ultrasound of Odontogenic Cutaneous Sinus Tract: An International Multicentric Experience and a Review of the Literature

Objectives: To investigate the role of high-resolution ultrasound (HR-US) in the initial and differential diagnosis of the Odontogenic Cutaneous Sinus Tract (OCST) in a multicentric setting. Methods: Skin HR-US examinations of OCSTs performed between January 2019 and June 2023 at different Institutions were retrospectively reviewed. Epidemiological and clinical data (age, gender, location of the skin lesion, causative tooth, and the clinical suspicion) as well as HR-US imaging findings (morphology and length of the sinus tract, Doppler signal, and cortical bone interruption of maxilla or mandible) were collected. US examinations were performed by expert radiologists using a high-performance US scanner, employing a high-frequency linear probe (15 MHz or higher frequencies). In only one patient the HR-US exam was integrated with strain elastography (SE). Results: Sixteen patients were enrolled with a median age of 37.6 years (range 16-70 years). The most frequent clinical suspicion was epidermal cyst, while OCST was suspected in only two cases. In all cases, HR-US depicted the sinus tract as a nodular, triangular or "champignon-shaped" lesion in the subcutaneous layer, which continued with a slightly tortuous band structure, up to the focally interrupted cortical bone plate. Furthermore, color Doppler evaluation showed color signals around and/or within the lesion, expression of inflammation. On SE, the sinus tract showed a hard pattern, due to fibrous and granulomatous tissue. Conclusions: HR-US, thanks to its high spatial resolution, allows the evaluation of OCST, and play a crucial diagnostic role, mainly when the clinical suspicious is different.