Fibrous dysplasia mimicking bone metastasis in nasopharyngeal carcinoma: a case report and literature review.

Fibrous dysplasia of bone (FDB) is a rare bone disease that may be misdiagnosed as bone metastasis in terms of some symptoms and imaging features. Therefore, the differential diagnosis between FDB and bone metastasis may be a challenge. To our knowledge, there are no reports in the literature to date regarding concomitant nasopharyngeal carcinoma (NPC) with FDB. The aim of this study was to report the case of a NPC patient with FDB, to highlight correct diagnosis and treatment. A 28-year-old young woman was investigated for accidental nasal bleeding. A mass on the right neck and local pain on right femur, and she was submitted to a standard imaging examination suggesting the presence of a solitary right femur metastasis from NPC. Then the patient was submitted to four cycles of chemotherapy, with a partial response (PR) for the mass in neck but no change in the bone metastasis. Because the bone lesion was single, pathologic biopsy was taken to confirm diagnosis. Surprisingly, it was a FDB instead of tumor. At five-year follow-up, she is free of recurrent disease. In this case, we believe that although NPC with FDB is rare, it should not be omitted when bone metastasis is suspected, especially when the metastasis is solitary, because it is crucial for diagnostic staging and treatment choice.