Rib destruction by epithelioid tumour in a young man

A man in his 30s presented with back pain and was found to have a tumour in the posterior chest wall. Imaging showed an expansile mass measuring up to 6.7 cm, centred on the left posterior 11th rib with diffuse cortical destruction. The tumour displaced the left hemidiaphragm, and was in contact with the spleen, with no infiltration seen. There was no involvement of the overlying skin. PET-CT showed the lesion to be inhomogeneously hypermetabolic, with a mainly peripheral distribution of FDG. Staging imaging showed no other abnormality. The patient was otherwise well with no medical history and no significant family history. A CT-guided biopsy was performed. Review the high-quality, interactive digital Aperio slide at http://virtualacp.com/JCPCases/jclinpath-2019-206338/ and consider your diagnosis. 1. Metastatic carcinoma. 2. Alveolar rhabdomyosarcoma (ARMS). 3. Sclerosing epithelioid fibrosarcoma (SEF). 4. Spindle cell/sclerosing rhabdomyosarcoma. 5. Osteosarcoma. 6. Ossifying fibromyxoid tumour (OFMT). This is a tumour composed of relatively uniform, minimally to mildly pleomorphic, medium-sized cells with round to ovoid nuclei and clear to lightly eosinophilic cytoplasm. The cells are present in groups, nests and occasionally individually, within densely fibrous stroma, with areas suspicious of osteoid formation. In this case the tumour is diffusely and strongly positive for MUC4 and CD99, and focally for CD57. This particular case is negative for AE1/AE3, Cam5.2, CK7, TTF1, desmin, smooth muscle actin (SMA), myogenin, FLI1, neuron-specific enolase, CD56, synaptophysin, chromogranin, glial fibrillary acidic protein, TLE1, CD45 and CD138. There is a normal staining pattern for p53, and INI expression is retained in nuclei. …