CT halo sign in cases of pulmonary metastasis from bone or soft tissue sarcoma

SummaryAimWe reviewed a series of patients with lung metastases from bone or soft tissue sarcoma to evaluate the frequency of the CT halo sign and CT features of metastatic lesions showing this sign.MethodsThe study included 19 patients with lung metastasis from bone or soft tissue sarcoma treated during a 4-year period at our institution. The CT halo sign was defined as a central pulmonary nodule surrounded by a distinct zone of ground-glass opacification (halo).ResultsThe CT halo sign was found in 4 (21%) of the 19 patients. One of the 4 patients had 2 nodules characterized by the CT halo sign; the others had 1. All 5 nodules with a halo had a well-defined margin. The long axis of the central nodules was 4–78 mm (mean, 25.4 mm). The area of the halo was extensive in 4 small nodules (long axis <25 mm). Histologic examination, performed in 1 case, showed that the halo corresponded to lepidic proliferation of tumor cells.ConclusionMetastatic nodules from bone or soft tissue sarcoma are sometimes characterized by a CT halo. The halo of small metastatic nodules can be large.