Hybrid central giant cell granuloma and central odontogenic fibroma-like lesions of the jaws E.W.ODELL, T.LOMBARDI, A.W.BARRETT*, P.R.MORGAN & P.M.SPEIGHT* Department of Oral Medicine and Pathology, UMDS Guy’s Hospital and *Department of Oral Pathology, Eastman Dental Institute, London, UK Date of submission 29 January 1996 Accepted for publication 12 August 1996 ODELL E . W. , LOMBARDI T., BARRETT A . W. , MORGAN P. R . & SPEIGHT P. M . (1997) Histopathology 39, 165–171 Hybrid central giant cell granuloma and central odontogenic fibroma-like lesions of the jaws Ten lesions from eight cases are presented of a rare intra-osseous jaw lesion with the combined histological features of giant cell granuloma and central odonto- genic fibroma. Lesions arose over a wide age range and presented as monolocular or multilocular radiolucen- cies with cortical expansion and, in one case, perfora- tion. Two lesions recurred after curettage, one being eradicated by a second curettage and one by conserva- tive excision. Histologically, zones of typical giant cell granuloma lay in a fibrous stroma containing islands, strands and clusters of epithelial cells. Islands often contained duct-like spaces or hyaline basement mem- brane globules. Trabeculae of osteoid were present in five lesions. Recurrent lesions showed features identical to the initial lesion, including recurrence of the prominent epithelial component. These features cannot be conclusively ascribed to a variant of either giant cell granuloma, central odontogenic fibroma or aneurysmal bone cyst, but the clinical features are slightly more suggestive of giant cell granuloma. Attention is drawn to the characteristic and potentially confusing histological appearances. The presence of giant cell granuloma-like areas in central odontogenic fibroma-like lesions is associated with an increased risk of recurrence following curettage. Keywords: odontogenic fibroma, odontogenic tumours, giant cell tumours, fibroma, granuloma, giant cell Introduction Three cases of an unusual intra-osseous lesion of the jaws which had histological features of both central odontogenic fibroma and giant cell granuloma were reported for the first and only time in 1992 1 . The combination was interpreted as an odontogenic fibroma in which there was a reactive giant cell component rather than a collision lesion or odontogenic fibroma with an associated aneurysmal bone cyst. In this report we present a further 10 examples of this rare lesion and emphasize its distinctive histological features. Materials and methods Ten lesions composed of both central giant cell granuloma and odontogenic fibroma-like tissue were retrieved from the archives of the Department of Oral Pathology, Eastman Dental Institute and the Depart- ment of Oral Medicine and Pathology, UMDS Guy’s Hospital, London. All had been treated by curettage. In two cases a single recurrence had followed curettage and both recurrent lesions were included in the study. Formalin-fixed paraffin-embedded tissue was cut and representative sections stained with haematoxylin and eosin and Perls’ stain. The histological appearances were compared with 28 gnathic central giant cell granulomas, three central odontogenic fibromas and 11 lesions of cherubism from seven cases in department archives. Immunocytochemistry for cytokeratins was per- formed on blocks for which there was no evidence or record of decalcification. Pan-cytokeratin immuno- staining was performed on sections trypsinised for 10 min in 0.1% trypsin before incubation with monoclonal antibody MNF116 (IgG 1 ; Dako—dilution 1:100) for 1 h. Sections for detection of cytokeratin 19 were subjected to microwave irradiation at 740 W in Histopathology 1997, 30, 165–171  1997 Blackwell Science Limited. Address for correspondence: Dr E W Odell, Department of Oral Medicine and Pathology UMDS, Floor 28 Guy’s Tower, Guy’s Hospital, London SE1 9RT, UK.