Quiz
WHAT IS YOUR DIAGNOSIS?

A 54-year old female presented with a progressive left chest wall pain associated with sneezing of 1 year duration. Her past medical history was significant for osteoporosis, mitral valve prolapse and Wolf-Parkinson-White syndrome. Physical examination was within normal limits. Chest X-ray showed a solitary well-defined bony lesion in the anterolateral aspect of the left 6th rib. An increased uptake on computed tomography (CT) and bone scan was noted. On MRI, the lesion measured 2.2 × 1 × 1.4 cm and showed a homogenous low signal intensity on T1 and heterogeneous high signal intensity on T2. There was no evidence of extra-osseous extension or other skeletal lesion identified. A portion of rib measuring 7.5 × 2 × 1.6 cm was excised which on sectioning revealed a well-circumscribed, grey-white lesion measuring 1.7 × 1.4 × 5 cm. Microscopically, it showed a well-defined lesion with thick shell of maturing cortical bone, noted at the periphery of the lesion (Fig. 1). The center of the lesion is composed of anastomosing woven bony trabeculae with intervening bland edematous fibrous stroma admixed with xanthomatous component (Figs. 2, 3). No mitotic activity was noted. The immature anastomosing woven bony trabeculae (arrow) and the thicker mature bony egg shell (star) were highlighted using polarizing light (Fig. 4).