Bizarre parosteal osteochondromatous proliferation (BPOP): Nora lesion
Presentation
Six-year history of mass on the plantar aspect of the left hallux. Denies previous trauma.
Patient Data
Anteroposterior and lateral radiographs of the hallux show a juxta-cortical calcified lesion of the distal phalanx on the plantar aspect, without cortical erosion (approximately 2 cm in size).
Surgery report
Intra-operative showed the multilobulated mass with the pseudocapsule on the planto-medial aspect of the distal phalanx of the hallux. It was removed with the pseudocapsule. No adherence to any of the surrounding bony or soft tissue structures.
Hystological report
Atypical cartilage with significant proliferative activity and disorganized ossification in the cartilage with plenty of calcified osteoid with benign osteocytes, and actively proliferating but benign fibrous tissue, consistent with a bizarre parosteal osteochondromatous proliferation.
Case Discussion
BPOP is a calcified or ossified mass with regular margins, arising directly from the cortical surface of the underlying bone. It usually has a broad base and the underlying cortex is intact. There is no periosteal reaction. Sometimes there is cortical erosion but the absence of continuity between the cortex and medullary cavity of the bone and the lesion. The radiographic features that differentiates BPOP and parosteal osteosarcoma is the cortical and soft-tissue infiltration and periosteal reaction, both absent in BPOP.
Case courtesy of Dr.ssa Laura Braccaioli
Radiographer: TSRM Fabio Imola
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