More diagnoses to consider
Other potential diagnoses for benign osteochondromatous lesions include bizarre parosteal osteochondromatous proliferations (BPOP) and digital mucous cysts.
BPOPs, also known as Nora’s lesions (crediting preliminary research performed by Nora and colleagues in 19834), are irregular formations of hypercellular cartilage, bone, and large chondrocytes. They predominantly occur in the small bones of the hands and feet, but may involve the skull and long bones.3 Unlike subungual exostoses and osteochondromas, BPOPs tend to occur in the third and fourth decades of life and generally do not alter, or have continuity with, the underlying bone.4
Histologically, BPOPs undergo irregular maturation, leaving a characteristic blue tint at the border of the newly formed trabecular bone. As with subungual exostoses, these lesions were traditionally believed to be reactive in nature. However, cytogenetic studies have identified variant translocations involving 1q32 (most commonly t[1;17] [q32;q21]) that are unique and common to these lesions.5
Digital mucous cysts are benign ganglion cysts that typically appear in the distal interphalangeal joints or at the proximal nail fold. They are believed to result from mucoid degeneration of connective tissue. Although generally associated with the hands, these cysts can also occur on the feet.6
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