Combined immunohistochemistry for the differential diagnosis of cystic jaw lesions: its practical use in surgical pathology.

AIMS Histopathological distinction of cystic jaw lesions, including odontogenic tumours, is challenging because their lining epithelia, which are basically stratified squamous epithelia, resemble each other, especially when they become hyperplastic from inflammatory reaction. The aim of this study was to seek practical measures to differentiate such lesions. METHODS AND RESULTS Nineteen surgical specimens from unicystic ameloblastomas (UAs), 17 from keratocystic odontogenic tumours (KCOTs), 13 from dentigerous cysts (DCs), 10 from lateral periodontal cysts (LPCs) and 20 from radicular cysts (RCs), all of which contained both typical flat and rete-peg-shaped lining epithelia, were examined for their immunohistochemical profiles. Among them, keratin (K) 10, K17, perlecan, proliferating cell nuclear antigen (PCNA) and UEA-I lectin binding (UEA) were selected as useful immunohistochemical markers for their differential diagnosis. K10 was positive (+) in KCOT and DC. K17 was not present in RC. Perlecan was found in UA, KCOT and LPC. PCNA+ cells were found frequently in UA and KCOT. These localization patterns were constant even when linings were not flat. CONCLUSIONS Using a combination of six kinds of immunohistochemical pattern, it is now possible to discriminate reliably and objectively these five cystic jaw lesions in routine practice.