Dural metastasis demonstrated on Tc-99m MDP bone scintigraphy in staging workup for a patient with breast cancer

An 80-year-old woman with multifocal invasive lobular carcinoma of the right breast treated 6 years previously with mastectomy, locoregional radiotherapy, and tamoxifen was referred for a bone scan to investigate generalized arthralgias. The patient reported right-sided headaches, blurred vision, and dizziness in the previous 3 months. The bone scan revealed a large area of unusual and abnormal Tc-99m methylene diphosphonate (MDP) uptake in the right frontoparietal skull region. CT and MRI of the brain were performed to evaluate the possibility of cerebral metastases. The CT revealed extensive abnormal thickening and enhancement of the dura in the right frontoparietal region. No calcification of the dura or bony destruction of the overlying skull was evident on CT. MRI similarly revealed extensive thickening and irregularity of the dura. The usual causes of increased skull Tc-99m MDP uptake on bone scanning such as skull metastases and dural calcification were not evident on CT or MRI.