C. Salicylic acid paste under occlusion. Subungual exostosis is an acquired, benign bony tumor that can affect any age group but most often is discovered in persons 10 to 30 years of age. It presents as a distal, subungual mass, usually on the dorsal-medial great toe. Fingernail lesions rarely occur. Subungual exostosis begins as a reactive fibrous growth that develops cartilage and ultimately ossifies.
Complete excision remains the treatment of choice, although recurrences are reported.
No gender or racial predilection has been noted. In children, the differential diagnosis includes subungual wart and pyogenic granulomas, while the most serious condition would be a neoplasm such as osteochondrosarcoma, squamous cell carcinoma or glomus tumor. Although the diagnosis can be made with a biopsy, radiographs to evaluate for bony involvement are recommended before biopsy of any subungual mass. In this case, if the physician were not prepared to remove bone, and expected only a soft tissue growth, the biopsy procedure would have been wasted. Use of overnight occlusion may make the treatment more effective by hyperhydrating the wart, which may allow deeper penetration of the caustic medication.