Osteofibrous Dysplasia-like Adamantinoma Mimicking Bone Metastasis in a Patient With Rectosigmoid Cancer

Abstract

A patient with underlying rectosigmoid cancer presented with solitary bone lesion at left tibia. Eventhough, solitary bone metastasis particularly in the appendicular skeleton is rare in rectosigmoid cancer, it remained as the most likely initial diagnosis. However, after further characterisation by various imaging modalities and subsequent biopsy, the lesion proved to be an osteofibrous dysplasia like-adamantinoma (OFD-like adamantinoma), which is a subtype of adamantinoma. Being a rare primary bone tumour, adamantinoma and its subtypes are infrequently thought of in the initial working diagnosis of a patient with known malignancy who presents with solitary bone lesion. We present here a case of OFD-like adamantinoma in a patient with underlying rectosigmoid cancer, which mimic a metastastic bone lesion.