Purpose: In this study, the efficacy of fine-needle aspiration biopsy (FNAB) and cytokeratin 10 immunocytochemical staining to differentiate odontogenic keratocysts (OKC) from dentigerous and other nonkeratinizing cysts was evaluated.
Patients and methods: This was a prospective study of 18 FNABs of odontogenic cystic lesions performed at the Massachusetts General Hospital between 1995 and 1998. A consistent and standardized technique was used to obtain the cytologic material. Immunocytochemistry was performed on destained smears by using a monoclonal antibody against cytokeratin 10. Identical immunohistochemical methods were applied to the final surgical specimen, and results were compared.
Results: Cells of 10 of 18 FNABs showed a markedly positive immunoreaction to anti-cytokeratin 10, supporting a diagnosis of OKC. In all 10 cases, the diagnosis was confirmed by histology. Six of 18 cases showed an absence of staining and were interpreted as anti-cytokeratin 10 negative. In the 2 remaining cases, there were occasional squamous cells on the smear with weak anti-cytokeratin 10 uptake. The overall pattern was negative, and these were interpreted as nonkeratinizing cysts. In all 8 of these cases, the diagnosis of OKC was excluded based on the immunocytochemistry, and the final histologic diagnoses were: dentigerous cyst (n = 4) and radicular cyst (n = 4).
Conclusions: The combination of FNAB with immunocytochemical determination of cytokeratin 10 expression by sampled epithelial cells was 100% accurate in distinguishing an OKC from a nonkeratinizing odontogenic cyst in this series. The technique allows for early diagnosis and rational surgical planning.