Protuberant Fibro-Osseous Lesion of the Temporal Bone: “Bullough Bump”—Multimodality Imaging Case Series and Literature Review

Abstract

A handful of cases of protuberant fibro-osseous lesions of the temporal bones have been described in the literature to date, with primary focus on the pathologic features. Here we review 3 cases of pathology-proved protuberant fibro-osseous lesions of the temporal bone and include a literature review with a focus on the imaging features. While rare, these lesions have near-pathognomonic imaging features defined by a location at the cortex of the outer table of the temporal bone at the occipitomastoid suture, lack of involvement of the underlying marrow, variable mineralization, and MR signal characteristics atypical of a chondroid lesion. One case in this series was FDG-avid and had occasional mitotic features, possibly reflecting an aggressive variant. Neuroradiologists should be familiar with this benign diagnosis to aid in timely identification and avoid unnecessary additional imaging.ABBREVIATIONS: FD ¼ fibrous dysplasia; PFOLT ¼ protuberant fibro-osseous lesion of the temporal bone P rotuberant fibro-osseous lesion of the temporal bone (PFOLT) was originally described by Selesnick et al, 1 in 1999. They presented 2 unique-but-identical cases of rightsided retroauricular exophytic fibro-osseous lesions in young patients emanating from the outer cortex of the bone near the occipitomastoid suture line. Almost 11 years later, Sia et al 2 reported 2 similar cases in 2010, and they proposed naming the lesion "Bullough lesion/bump" after Professor Peter Bullough, who described the pathologic features in the original case report in 1999. To date, 10 similar cases have been reported in the literature. These lesions have near-pathognomonic imaging features, defined by a location at the outer table cortex of the temporal bone at the occipitomastoid suture, lack of involvement of the underlying marrow, variable mineralization, and MR signal characteristics atypical of a chondroid lesion. The goal of this article is to report a multi-institutional series of this lesion, to discuss the clinical characteristics and unique imaging features of the lesion, and to review the existing cases in the literature. Case SeriesInstitutional review board approval was waived and not required for this retrospective case series. Three cases were identified from 3 different institutions in New York City between 2015 and 2020.Demographic information was obtained from the electronic medical record, including age, clinical presentation, imaging findings, and histopathologic diagnosis.

Unusual Protuberant Lesion of the Temporal Bone (Bullough Lesion)

“…Imaging characteristics of protuberant fibro-osseous lesion of the temporal bone were described by Shekhrajka et al (2). CT characteristics include involvement of only the outer cortex of the temporal bone at the occipitomastoid suture, distinct margins, protuberance, and lack of bone marrow involvement.…”

“…The lesion can have varied calcification patterns. MRI characteristics include T2 hypointensity with mild heterogenous enhancement (2). These characteristics are all similar to the lesion presented in this report, which can be seen in Figures 1 and 2.…”