Protuberant fibro-osseous lesion of the temporal bone: Bullough's lesion

Primary tumors of the calvarium are infrequent, and with the exception of osteoma, lesions confined to the surface of the skull are very rare. The differential diagnosis includes benign and malignant matrix forming tumors, other mesenchymal tumors, and reactive lesions. Fibro-osseous lesions are characteristically centered within bone and surface fibro-osseous lesions always prompt consideration of parosteal osteosarcoma, which is rare but well documented in the calvarium. We present 2 cases of a distinctive lesion of the temporal bone intimately related to the occipito-mastoid suture and typically presenting as a retroauricular soft tissue mass with calcific densities, confined to the soft tissues on the outer table of the skull without intraosseous involvement. The lesion is characterized histologically by rounded and ovoid zones of ossification within a bland fibrous stroma. The first 2 cases were documented in 1999 as "Protuberant fibro-osseous lesion of the temporal bone." We present a further 2 cases, 1 of 2 years duration and the other with a 10-year history. This distinctive entity, which must be distinguished from other fibro-osseous lesions, including subtle low-grade parosteal osteosarcoma, seems to behave in a benign fashion and thus far recurrence is not documented. Local excision seems adequate. The pathologic features in the original report were documented by Prof Peter Bullough. As these cases were recognized by him alone we propose calling this entity "Bullough lesion" or, better still, " Bullough's Bump!".