Imaging and histopathological characteristics of carcinoma-induced bone formation in skeletal muscle

An 11-year-old neutered male Groenendael canine presented with suspected neoplastic disease associated with pelvic limb lameness. Clinical examination revealed firm and thickened ventral abdominal musculature, pitting oedema with a spiculated texture within pelvic limb and inguinal subcutaneous tissues, sublumbar lymphadenopathy and multifocal hard foci along the floor of the pelvic canal. CT revealed a severe active polyostotic periosteal reaction and muscular mineralisation of the hindlimbs and caudal trunk. Skeletal muscle biopsy revealed a histopathological diagnosis of metastatic carcinoma with chondroid osseous metaplasia characterised by ossification (bone formation) within the tissue matrix. Paliative therapy was provided for the dog for two weeks before being euthanized.