Sequestra in primary lymphoma of bone: prevalence and radiologic features

Our objective was to determine the prevalence and spectrum of radiologic features of sequestra (detached pieces of bone separated from the involved segment) in cases of primary lymphoma of bone. This is a feature of primary lymphoma of bone that, to our knowledge, has not been reported previously. Recognizing sequestra is important, because a limited differential diagnosis of entities exists when this finding is seen.

We retrospectively reviewed all the clinical and pathologic information and radiologic studies in our archives on 434 cases of skeletal lymphoma. Of these, 246 met our criteria for consideration as cases of primary lymphoma of bone. All cases were pathologically proved. Plain radiographs were available for review in all cases, and CT scans were available in 46. Data on the presence or absence of sequestra, their size and appearance, the bone involved, and the site of involvement were recorded in each case.

Sequestra were noted in 28 (11%) of the 246 cases. The size varied from 2 to 45 mm (average, 12 mm), and multiple sequestra were seen in 17 cases. They were seen in the long bones (15 cases), axial skeleton (10 cases), and three other sites (scapula, calcaneus, and third metatarsal).

Sequestra have been reported in a variety of conditions, including osteomyelitis, eosinophilic granuloma, fibrosarcoma, malignant fibrous histiocytoma, and desmoplastic fibroma. Because sequestra were seen in 11% of the cases of primary lymphoma of bone reviewed in this study, we believe that lymphoma should also be included in the differential diagnosis when a sequestrum is noted on imaging studies.