[Adamantinoma of the tibia].

Adamantinoma ofthe tibia is not a common lesion, but because ofits somewhat anomalous features and confusing histological picture it continues to arouse the interest of clinicians and pathologists. Much of the interest stems from the term adamantinoma which was first used by Fischer (1913) to describe a primary bone tumour involving the tibia. He used the term adamantinoma because of its resemblance to the ameloblastoma of the jaw. Until 1940 adamantinoma of the long bones had been described only in the tibia. Since then it has been found in other long bones and also in some short bones (Anderson and Saunders 1942, Moon 1965). In 1954 Baker, Dockerty and Coventry in a review of the then published cases set out the clinical picture of the condition. There is an equal incidence in the sexes. The age range is from twelve to fifty-seven years. The predominant site is the tibia although single cases have been reported in the femur, fibula and ulna. There is usually a history of trauma, and pain is the main symptom. The duration of the pain may range from six weeks to several years. The radiographic appearances, which are not diagnostic, show cystic and multicystic patterns with cortical destruction and some periosteal reaction. Macroscopically the tumour is pale, grey or white. The consistency is described as firm, elastic, brain-like, sometimes soft or even gritty. There are cystic cavities which may contain straw coloured or bloodstained fluid. The tumour may involve the cortex and may penetrate the periosteum and soft tissues. Calcification may occur (Donner and Dikland 1966). Neither teeth nor enamel tissue have been found in any of the cases reported to date. The microscopic appearances vary from case to case. Three patterns are described (Baker and colleagues 1954): 1) Masses of epithelial cells are seen in islet formation, around the periphery of which columnar cells are arranged in palisade fashion. The central masses show stellate cells in a reticular formation. There are cystic areas in the centre of the reticulum. This type could be mistaken for an adenocarcinoma. One case is recorded in which secondary carcinoma was diagnosed as adamantinoma (Ackerman and Spjut 1962). 2) Islands of cells resembling basal cells are scattered throughout a fibrous stroma. Palisading of the peripheral cells occurs. Cystic areas are present with epithelial masses reminiscent of basal cell carcinoma. 3) Squamous epithelial islands are scattered throughout a fibrous stroma. There is evidence of pearl formation. Because of the tumour’s protracted course, it was believed for many years to be benign or at most only locally malignant. Local excision was advocated but this proved ineffective. Radiotherapy was also recommended, either alone or combined with local excision (Rehbock and Barber 1938, Rankin 1939, Hebbel 1940). It is now known that the incidence of local recurrence is high and that radiotherapy is ineffective. Metastases have been reported in several cases (Mangalik and Mehrotra 1952 ; Baker and colleagues 1954 ; Morgan and Mackenzie 1956; Naji, Murphy, Stasney, Neville and Chrenka 1964). Once the diagnosis is clear from the biopsy specimen amputation is recommended. Delay increases the risk of metastasis.