Aggressive osteoblastoma of the proximal humerus.

A nine-year-old boy presented with increasingly worsening right shoulder pain of 18 months' duration. On physical examination, there was a tender firm swelling over the right upper arm. Radiographs showed a large osteolytic lesion in the proximal humeral diaphysis, with prominent mixed acute-on-chronic periosteal reaction in a lamellar fashion. There was a pathological fracture. The lesion appeared to be radiographically aggressive in nature. Bone scintiscan showed solitary marked uptake. On-table frozen section histopathological examination of the lesion showed an osteoblastic lesion with aggressive features. Completion curettage and high speed burring of the cavity was performed. In view of the patient's young age, which required a biological solution, and potential for local recurrence, that necessitated a radiopaque filler, the lesion was packed with a calcium phosphate cement paste. The final diagnosis was osteoblastoma with aggressive features. The patient remained well on follow-up to date. The filler continues to be remodelled to native tissue and there is no evidence of local recurrence. Osteoblastoma is a relatively rare benign tumour that typically occurs in the posterior elements of the vertebral column. The humerus is a very rare site of disease in the appendicular skeleton, and poses a diagnostic dilemma which implicates the possibility of osteogenic sarcoma.

Clinics in diagnostic imaging (87). Subcutaneous lipoma.

A 40-year-old man presented with recent increase in size of a painless long-standing soft mass over the right shoulder. Magnetic resonance (MR) imaging showed a lobulated mass located within the subcutaneous layer overlying the deltoid muscle. It was homogeneously T1-hyperintense, T2-hyperintense, and non-enhancing. Signal characteristics were those of a simple lipoma. The diagnosis was confirmed on histopathological examination of the excised specimen. Musculoskeletal lipomas are discussed, with emphasis on their characteristic appearances on various imaging modalities, and illustrated by additional examples.