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Adamantinoma of the long bones. A clinicopathological study of thirty-two patients with emphasis on histological subtype, precursor lesion, and biological behavior.

The records of thirty-two patients who had had an adamantinoma of the long bones were examined to investigate the relationship between the clinical presentation, the histological subtype, and the method of treatment, and the clinical result. All histological patterns of differentiation that are characteristic of adamantinoma were observed, including the basaloid, spindle-cell, tubular, squamous, and osteofibrous dysplasia-like subtypes. Follow-up data were available for twenty-eight (88 per cent) of the thirty-two patients. These patients were followed for a mean duration of 122 months (range, eleven months to twenty-nine years and two months). Nine patients (32 per cent), all of whom had been managed with an intralesional or marginal procedure, had a local recurrence of the tumor after a mean disease developed in three of the nine patients. In five other patients, metastasis developed without having been preceded by a local recurrence. Thus, the over-all rate of metastasis was 29 per cent (eight patients). The mean duration of survival for the patients who had metastasis was twelve years and eight months. Statistical analysis of various clinicopathological variables revealed intralesional or marginal excision to be the most significant risk factor for a local recurrence or metastasis (p < 0.001). Two patients who had had a presumed osteofibrous dysplasia-like adamantinoma, which contained few isolated keratin-positive epithelial cells within the stroma at the time of presentation, had a full-blown adamantinoma at the time of the local recurrence. Although the clinical course that was observed may be the result of a sampling error, it poses questions as to the regressive nature of osteofibrous dysplasia-like adamantinoma. On the basis of our findings and the data in the literature, we believe that an osteofibrous dysplasia-like adamantinoma may be a precursor lesion of the classic type of adamantinoma.