Aneurysmal bone cysts (ABC) are rare, benign primary bone tumors. Although benign, they can be locally aggressive resulting in erosion of bone and surrounding tissues over time. In later stages, depending on the clinical urgency, immunotherapy or surgical resection remain treatment options. This report illustrates a case of a 32-year-old female who presented with chronic worsening low back pain without neurological deficits. Radiological imaging revealed a large destructive mass arising from the thoracic spine invading into the central canal, causing critical central stenosis and cord compression. Histopathology revealed ABC. This case highlights the importance of including ABCs and other ‘benign’/locally aggressive lesions in the differential of patients with insidious musculoskeletal complaints. This case also demonstrates that one can be neurologically asymptomatic despite having critical central canal stenosis and cord compression if the causative lesion is slow growing. Understanding this allows us to arrange for most appropriate management.

Hibernomas are a very rare and benign soft tissue tumour that originate from brown adipose tissue. While they are not histologically malignant, they may be indistinguishable from aggressive tumours such as liposarcomas on imaging. It is, therefore, important to consider it as a differential diagnosis when a suspicious fatty lesion is seen on imaging. This may prevent unnecessary invasive surgery and patient stress. This paper illustrates the clinical presentation, radiological features, and histological diagnosis of a patient with a rare dumbbell-shaped hibernoma in the pelvis.