Track

Abstract

Bizarre Parosteal Osteochondromatous Proliferation (BPOP), also known as Nora's lesion, is a rare, benign bone tumor that often affects the small bones of the hands and feet with increased propensity for local recurrence. Precedent cytogenetic studies have identified 2 mutually exclusive chromosomal rearrangements including t(1;17) and inv(7) in BPOP. Recently, specific gene fusions and gene mutations, particularly involving COL1A2::LINC-PINT and COLC1A1::MIR29B2CHG and mutations involving COL1A1. However, COL1A2::MIR29B1 gene fusion has not been previously described in BPOP. Herein we describe a case of BPOP with a novel COL1A2::MIR29B1 gene fusion in BPOP in a a middle-aged female. A 45-year-old female presented with recurrent mass in the right index finger (IF). Prior excision performed 9 months ago was diagnosed as possibly heterotopic ossification or chondroma. The patient reported some discomfort but no associated numbness, tingling, weakness or extensor lag. Radiologic studies showed heterogeneously enhancing partially ossified mass at the involving the dorsal aspect of the second metacarpal neck with peripheral rim of T2 hyperintensity. A surgical resection performed showed a variable mixture of disorganized cartilage, bone and fibrous tissue. Disorganized cartilage was observed as outermost layer with large, atypical chondrocytes transitioning into trabeculae of bone via endochondral ossification with an irregular interface. The surgical margins were negative. RNA-fusion panel by Next Generation Sequencing (NGS) was positive for COL1A2::MIR29B1 gene fusion, confirming the diagnosis. Patient is 20-months post-surgical resection with no evidence of recurrence. In summary, we identify a novel COL1A2::MIR29B1 gene fusion in BPOP, that has not been previously characterized.