BizarreParosteal Osteochondromatous Proliferation (Nora's lesion) with translocation t(1;17)(q32;q21): a case report and role of cytogenetic studies on diagnosis.

Bizarre Parosteal Osteochondromatous Proliferation (BPOP) is a benign tumor-like lesion that has recently been reported to have an association with a specific translocation t(1:17)(q32;q21)[1]. Like other reactive periosteal lesions, BPOP can be diagnostically challenging, with the ever-present possibility of a potentially devastating erroneous diagnosis of malignancy. These lesions are often clinically, radiologically and histopathologically ambiguous, with rapid but circumscribed, non-infiltrative growth patterns, and histological atypia, but without overt features of malignancy. However, recent published reports have better characterized radiological [2] as well as histological features that aid in making an accurate diagnosis. In spite of all these advances, one of the biggest challenges in making the correct diagnosis still remains the inexperience of the practicing pathologist with this lesion, simply due to its rarity. We present a case of Nora's lesion in the distal ulna of an 8 year-old girl, in which, besides the histological features, we were able to demonstrate the translocation t(1:17)(q32;q21). Thus, we would like to emphasize the utility of cytogenetic studies in the correct and rapid diagnosis of clinically and radiologically ambiguous periosteal-based lesion.