Hematopoietic Islands Mimicking Bony Metastases in Cancer Patients

Introduction Hematopoietic islands of the periphery skeleton are common. Focal nodular hyperplasia of the hematopoietic bone marrow in the axial skeleton is rare, but it can mimic metastases.

Material and Methods Six patients with a mean age of 61.2 years (range: 50–67 years) who had an unclear bone lesion that was imaged with magnetic resonance imaging (MRI) and computed tomography (CT) were included retrospectively. Five of these patients had known cancer (83.3%). The gold standard was biopsy in four cases and long-term follow-up in two patients.

Results The location was the thoracic, lumbar, or sacral spine in five cases and the rib in one patient. One patient presented with four vertebral body lesions; all other patients had one lesion each. The mean diameter of the lesions was 1.6 cm (range: 0.8–2.5 cm). All lesions showed slight hypointensity in T1-weighted and hypointense signal in T2-weighted images. On short tau inversion recovery, they showed isointense to slightly hyperintense signal. After contrast agent administration, no or only slight enhancement was observed. CT showed neither lytic changes nor sclerosis. All bone lesions showed a constant size on follow-up MRI. The CT-controlled biopsies were all inconspicuous and ruled out malignancy. Signs of increased hematopoiesis could be detected.

Conclusion So-called hematopoietic islands show a characteristic signal behavior in MRI that should not be confused with bony metastases.