The Differential Diagnosis of Periosteal Bone Lesions

Abstract

When we palpate the involved bone in what I term a periosteal lesion, we feel something outside the shaft and it does not feel like a bone shell or a circumscribed expanding tumor, as in the central tumor when the bone is destroyed. This palpable periosteal mass may be spindle in shape, and it is important to record here that the older view that such a spindle-shaped, palpable tumor indicated malignancy is incorrect. The first differentiation, then, between a central and a periosteal bone lesion is by palpation, and with the rarest exception, by palpation alone should one make the differential diagnosis. Remember, most periosteal lesions, both benign and malignant, attack the shaft rather than the epiphysis, while central lesions are almost equally divided between the shaft and the epiphysis. An age under fifteen in the central lesion is helpful in excluding malignancy, but not so in the periosteal lesion. No one has attempted recently to classify, on palpation, periosteal lesions. Before the days of X-rays the older surgeons were very expert in palpation, and the older books have clear descriptions, but these surgeons saw the lesions so late, and their ability to differentiate, even after amputation, between the benign and malignant was so faulty, that unfortunately these remarkable descriptions of the palpable periosteal mass were not helpful. When one can palpate a periosteal lesion as bone just as distinctly as one's shin bone, the chances are that it is not sarcoma, and when it feels irregular like a coral and one can feel a distinct pedicle, an exostosis may be diagnosed. The great difficulty in differentiating between the benign and malignant in periosteal lesions, both on palpation and in the radiograph, is due to the positive knowledge that excessive bone formation may be present both in sarcoma and in inflammatory lesions. An absence of bone formation is also observed in both the benign and malignant lesions. What are the periosteal lesions of benign character which, on palpation and in the X-ray, suggest the possibility of periosteal sarcoma? Fracture. When a fracture heals the periosteal bone gives rise to a spindle-shaped palpable tumor, and in the early stages, in the radiograph, the periosteal shadow is not unlike a form of periosteal sarcoma with bone formation in the periosteal tumor. As a matter of fact, I have had three X-rays of fractures referred to me with the diagnosis of periosteal sarcoma. One involved the phalanx of a finger and two the metacarpal bones of the foot. In all three one could see the fracture without displacement. It is very unusual to see fracture in periosteal sarcoma, except in a late stage, when diagnosis presents no difficulties. In these three cases of fracture sent to me with the diagnosis of sarcoma, I could observe in all the marrow shadow “pin callus” of new bone formation of less diameter than the periosteal shadow.