Objective: To fix a gray zone left in Tessier's classification of rare clefts with cleft 6 and to give a more comprehensive description of cleft 6 anatomy.
Design: The material used for the research was a series of 26 clinical cases of patients with assessed cleft 6 and 44 cases found out of a literature review with enough data to be useful. The 70 cases were cross-examined by the authors.
Study setting: The authors are senior craniofacial surgeons working in high-case load department from university centers where the patients are documented and receive primary as well as secondary treatment and follow-up.
Patients: The patients were selected out of the series of craniofacial deformities taken care of by the authors' department as rare clefts.
Main outcome: We describe the full spectrum of cleft 6 as an autonomous entity that could present itself in three subtypes: 6a is the most proximal and could be associated with cleft 8. The subtype 6b is medial toward the zygomatic arch and frequently associated with a bone and teeth appendage (frequently described as a "maxillary duplication"). The subtype 6C goes toward the external ear between the helix crus and the auditory meatus.
Conclusions: The Tessier's opinion is that Treacher Collins syndrome was the association of clefts 6, 7, and 8 and is no longer sustainable in the light of modern genetics. Most of the cleft 6 are misdiagnosed in the literature.
Keywords: Tessier's cleft; Treacher Collins; cleft 7; cleft 8; cleft palate; craniofacial malformation; craniofacial surgery; hemifacial microsomia; macrostomia; mandibulofacial dysostosis; maxillary duplication; oblique facial cleft; rare clefts.