ANEURYSMAL BONE-CYST AND GIANT-CELL TUMOR OF THE FOOT

From 1950 to 1994, 257 cases of benign bone tumors of the foot were tr eated at the Bone Tumor Center of the Rizzoli Institute, Aneurysmal bo ne cysts (ABC) and giant cell tumors (GCT) are rare and often they are misdiagnosed, To define the clinical and radiographic features useful for diagnosis, x-rays of 24 ABCs and 21 GCTs of the foot were reviewe d, Adding our series to the cases reported in the literature, the only important clinical data that emerged was the average age of patients affected by ABC and GCT (15 and 27 years, respectively). ABCs localize d in small tarsal bones were rare (6%), whereas 19% of GCTs were found in this site, The eccentric, round shape of a lytic lesion was more c haracteristic of GCT, An aggressive pattern of radiographic bone destr uction was observed more frequently in GCT than in ABC (P = 0.01). Sep tation was seen in both tumors, Typical of ABC was a sharp and trabecu lated margin, whereas GCT had an ill-defined edge with normal cancello us bone (P = 0.007). The growth of ABCs often expanded the cortex, whi le GCTs eroded, thinned, and broke the cortical bone (P = 0.001). A sa ucerized cortex was observed only in ABCs, A bony shell was more chara cteristic of ABC than of GCT (P = 0.002). Pathologic fractures (67%) a nd joint involvement, evaluated by computed tomography and magnetic re sonance imaging (83%), were more frequent in GCTs, whereas fluid level s were more frequently observed in ABCs (47%). The majority of the tum ors were stage 2, but GCTs represented 70% of stage 3 aggressive lesio ns.