An immunohistochemical study of keratin expression in ameloblastoma from a Kenyan population.

OBJECTIVES: Ameloblastomas appear to exhibit biological heterogeneity and, except in the case of malignancy, histological appearances that do not always allow their behaviour to be predicted. The aim of this study was to assess keratin expression in African ameloblastomas and to correlate this with their clinical and histological features. MATERIALS AND METHODS: Expression of simple keratins 7, 8, 18 and 19; cornification keratins 1 and 10; basal and differentiation keratins 5 and 14 and hyperproliferation-related keratins 6 and 16 in 14-39 cases of ameloblastoma was assessed by immunohistochemical methods. RESULTS: There was patchy expression of keratin 7 in the suprabasal and stellate reticulum-like cells in some cases. All cases showed similar weak expression for keratins 8 and 18 in suprabasal and stellate reticulum-like cells but none showed keratin 1 or 10 expression. There was intense expression of keratins 5, 14 and 19 by all tumour cells suggesting that they may retain basal cell characteristics with a potential for proliferation. No consistent relationship was seen between histological types and keratin expression pattern. However, keratins 6 and 16, expressed by suprabasal and stellate reticulum-like cells, showed a marked variation within and between cases, with the highest levels of expression in squamous strands. CONCLUSIONS: We propose that squamous strands may represent the sites of most active growth within individual tumours and expression of keratins 6, 16 and 19 may be predictors of rapid growth. There is a need for further investigation of this in longitudinal clinical studies.

Ki-67 antigen in ameloblastomas: correlation with clinical and histological parameters in 54 cases from Kenya.

The aim of this study was to assess the cell proliferation in ameloblastomas and to correlate this with clinical features and histology. Immunohistochemistry with Ki-67 monoclonal antibody was performed on fresh tissue from 54 ameloblastomas. A labelling index (LI) was calculated by expressing the percentage of Ki-67 positive cells. There was no significant correlation between LI and clinical features: age, sex or tumour size. Follicular ameloblastomas had significantly higher LI (5.0 +/- 0.5; mean +/- SEM) than plexiform tumours (3.2 +/- 0.6; P < 0.05). Plexiform ameloblastomas from the anterior mandible had a significantly lower LI (1.8 +/- 0.5) than those from the posterior (3.9 +/- 0.8; P < 0.05). LI was higher in squamous arcades (6.4 +/- 3.1%) than in epithelial cords and cysts (1.4 +/- 1.3%; P < 0.001). These results suggest that LI correlates most closely with the histological pattern of the epithelium of ameloblastoma, both within and between different tumours.