Parosteal lipoma of the rib: A rare condition in an uncommon location

Summary A 36‐year‐old female patient was diagnosed with a parosteal lipoma arising from the left 3rd rib. This was preluded by a 5‐year history of an asymptomatic and stable mass at the medial aspect of the left scapula. It had displayed an interval enlargement in the preceding 3 months which prompted investigation to rule out an aggressive lesion. The patient was investigated with CT, MRI and PET scan which demonstrated a well‐circumscribed juxtacortical fatty mass with osseous excrescence and no enhancing soft tissue components or FDG avidity in the fatty component, in keeping with a parosteal lipoma. CT‐guided biopsy allowed histopathological correlation which facilitated the exclusion of an aggressive lesion and supported the imaging diagnosis. This case is a pertinent educational tool for radiologists and orthopaedic surgeons as it characterises a rare and benign pathology in an uncommon location, with mimicry of malignant differential diagnoses such as liposarcoma and chondrosarcoma. We aim to bring awareness to this condition and its typical imaging characteristics and thus allowing radiologists to make more confident conclusions in future cases.