Oral fibrous histiocytoma and its angiomatoid variant.

Fibrous histiocytomas are uncommon mesenchymal tumours of the soft tissue in the head and neck region. We report two cases that occurred in the oral cavity, one of a benign fibrous histiocytoma (BFH) and another of an angiomatoid variant of fibrous histiocytoma (AFH). BFH is a benign neoplasm composed of cells with fibroblastic and histiocytic characteristics, while AFH is considered as a distinct type of fibrous histiocytoma with an intermediate malignancy grade that combines features of both fibrohistiocytic and vascular neoplasm. We describe the clinicopathological and histological characteristics of these lesions to clarify and facilitate their diagnosis. In the BFH case, the surgical specimen had many histiocytes positive for lysozime, whereas the AFH cells showed positivity for endothelial cell marker (anti-CD34 antibody). In both cases the tumours were positive for fibronectin and negative for S100 and SMA. Ki-67. Immunohistochemistry was performed in all cases to reveal the different mitotic activity between AFH and BFH tumour cells. Finally, differential diagnoses and therapeutic treatments are discussed.