How To Diagnose Benign Bone Tumors In The Lower Extremity

By Bradley W. Bakotic, DPM, DO

While some researchers have suggested that bone tumors affect the feet in a disproportionately small number of cases, one must keep in mind that most major studies on the subject have been assembled at major centers for the treatment of cancer.1,2 Therefore, lesions that have clearly benign clinical or radiologic features are largely omitted. Also be aware that most tumors of the bones of the distal extremities may be readily biopsied or excised, histopathologically evaluated and treated in a community hospital setting. These lesions would similarly never find their way into the files of large cancer centers or consultation services. In order to identify bone tumors of the feet accurately, one must understand the relative frequency with which various tumors of bone occur in that location. Occasional tumors of bone such as Dupuytren’s (subungual) exostosis occur in the feet in the vast majority of cases. In contrast, osteochondroma, the most common benign bone tumor, is rare in the small bones of the feet. Though many large bone tumor series have grouped lesions of the hands with those of the feet, even these sites are affected at different rates. In 1997, Ostrowski and Spjut published a series of 240 “lesions” of the bones of the hands and feet.3 They noted a relatively large number of reactive or reparative lesions of bone within their series. They identified conditions such as florid reactive periostitis, bizarre parosteal osteochondromatous proliferation (Nora’s lesion) and giant cell reparative granuloma at a much higher rate than has been described outside of the hands and feet.3 Alternate investigators have recorded similar findings and added Dupuytren’s (subungual) exostosis to their list of reactive lesions.4 A curious finding in the series by Ostrowski and Spjut was the paucity of Dupuytren’s (subungual) exostosis among their reported cases as it only accounted for one of the 240 cases in their series.3 The authors did not elaborate on this finding or why osteochondromas outnumbered Dupuytren’s exostosis six to one among their cases, although these findings seem to contrast sharply with other reports on the subject.1,4-6 It is reasonable to assume that at least some Dupuytren’s exostoses in their series were misdiagnosed as osteochondromas. In keeping with the high number of reactive or reparative bone lesions that have been reported in the bones of the hands and feet, there is an overwhelming predominance of benign lesions, as compared to malignant lesions, in these locations. The ratio of benign to malignant in various series has ranged from 5:1 to 21:1.3,4 This ratio differed somewhat from the 1.2:1 benign to malignant ratio reported in a series of pedal bone tumors assembled at the Memorial Sloan-Kettering Cancer Center.5 The authors of this latter series attributed the relatively few benign lesions in their study to the fact that their cases were assembled in a center that specializes in the treatment of cancer. This source certainly led to a bias toward malignant tumors by largely eliminated lesions that were radiologically, and/or histopathologically, benign from their series. For the purpose of discussion, we’ll divide bone lesions of the small bones of the feet into three categories: reactive/reparative lesions, benign neoplasms and malignant neoplasms. The prevailing thinking is that reactive/reparative lesions of bone are non-neoplastic proliferations or hyperplasias that are incited by trauma or stress in most cases. In contrast, neoplasms are autologous new growths that are clonal in nature in that they emanate from a single genetically identical “mother cell.” In most cases, neoplasms do not form in response to trauma or involute upon removal of a stimulus. What You Should Know About Reactive/Reparative Lesions We will begin by summarizing the non-neoplastic lesions most commonly seen in the bones of the feet.

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