A sinister cause of high bone mass

Objective: To present an unusual case of high bone mass (HBM) in a patient subsequently diagnosed with metastatic breast cancer. Methods: We describe the clinical presentation of our case and discuss its management. Results: A 41-year-old woman with pancytopenia was referred for HBM. Initial evaluations for malignancy, osteopetrosis II, mastocytosis, hepatitis C, and fluorosis were negative including normal whole body bone scan, mammogram, and 2 iliac crest bone marrow biopsies. Three months after initial presentation, she was hospitalized for abdominal pain, nausea, and vomiting. A CT scan of the abdomen and pelvis revealed diffuse bowel wall thickening and endoscopy showed friable mucosa throughout the GI tract. Pathology showed metastatic lobular breast carcinoma. The patient was treated with chemotherapy and had good responses of tumor markers, GI symptoms, and bone marrow function. Conclusion: Clinicians should be aware of the possibility of occult malignancy as a cause of HBM, even in the absence of the overt findings suggestive of metastatic bone disease.