Fibromyxomata of the jaws

Abstract

In t rodue t ion . -The fibromyxoma of the jaw despite a deceptively benign histological appearance may show a clinical behaviour more suggestive of malignancy. This invasive tendency has been recognised by others (Trauner, 1942; Wawro & Reed, 195o; Hayward, I955; Sharer et aL 1963). During the past four years, four intra-osseous turnouts of this distinctive type have been seen and the purpose of this paper is to emphasise certain aspects of their clinical course. Although it is impossible to reconcile some statements made about fibromyxomata, nevertheless there is general agreement about their more important clinical features. Like many bone tumours they present as a palpable and often painless swelling or are found incidentally on radiological examination. No difference in sex incidence has been noted but it is stated that occurrence is most frequent in the second and third decades of life. In the present study the youngest patient at diagnosis was 28 years of age, and the eldest 47. In both the mandibular and maxillary cases, a posterior area was involved and, according to the published statistics of Zimmerman & Dahlin (I958) this location is more common than the anterior region. A uniform radiographic pattern cannot be ascribed to the fibromyxoma but the multiloculated type may have special distinguishing features. Straight septae divide the radiolucent image into square, rectangular or triangular spaces with the central portion traversed by fine, gracile trabeculations (Stafne, 1963). This structure has been described by Sonesson (195o) as being similar to that of the strings of a tennis racket. As the central tumour grows outwards the overlying cortex may be expanded to a thin shell, and occasionally the outer plate is perforated. Classically, a scalloped sclerotic rim outlines the radiolucent area, but this may be absent and then the margin shades off imperceptibly into normal bone. Recognition of the tumour depends upon its characteristic appearance at operation and the histological pattern. The abnormal tissue consists of widely spaced stellate and spindle cells with long processes lying in a mucinous matrix (Fig. I). Occasional mitotic figures, atypical cells and hyperchromatic nuclei may be seen in a field, and it is the presence of such morphological abnormalities which give the neoplasm a more ominous character (Fig. 2). Macroscopically the fibromyxoma is ivory white in colour and of firm consistency with a smooth or lobulated shiny surface. With the endosteal type of tumour there is usually no evidence of encapsulation, and the lesion tends to sweep through the bone leaving occasionally islands of unresorbed bony tissue (Fig. 3).