Shoulder pain and immobility comprise a multifactorial disorder apparently affected by pain inhibiting joint motion. As the syndrome is very common, many patients do not undergo detailed imaging studies before treatment. This study compared a series of 7 patients in whom a neoplasm was the underlying cause for the stiff shoulder with a series of 50 patients with primary or secondary frozen shoulder. In addition to a detailed history being taken, the Disabilities of the Arm, Shoulder, and Hand (DASH) upper limb outcomes data collection questionnaire was completed and physical examination, radiography, ultrasonography, and bone scanning were performed in all cases. In the cases of tumor, the presenting symptom was a stiff shoulder without radiographic abnormality in 7 of 67 patients with shoulder girdle neoplasms who were seen at our musculoskeletal oncology clinic. The tumors included osteoid osteoma, osteoblastoma, metastatic carcinoma, chondrosarcoma, periosteal lipoma, and acute lymphoblastic lymphoma. The diagnosis was established in all cases by an area of focal isotope uptake demonstrated by a routine technetium 99 methylene diphosphonate bone scan. In a single case of metastatic colon carcinoma, the diagnosis could only be established by magnetic resonance imaging, as the radiographs were normal and the bone scan demonstrated diffuse uptake over the proximal humerus. The patients whose frozen shoulder was caused by an underlying tumor were significantly younger and had a lower fatigue/energy dimension score on the RAND Short Form-36 health survey. The most useful diagnostic test appears to be a discrete area of bony tenderness, present in 7 of 7 patients with tumor and in only 5 of 50 patients in the control group. Although an underlying tumor is a rare cause of frozen shoulder syndrome, the potential grave consequences of misdiagnosis and the possibility of performing an unnecessary and ineffective invasive procedure should prompt physicians to increased vigilance. In patients with discrete bony tenderness elicited by light tapping, a bone scan should be ordered and magnetic resonance imaging should be considered.