Concurrent diagnosis of oropharynx cancer and bone sarcoidosis mimicking metastasis.

Bone location is uncommon in both sarcoidosis and in neck cancer (HNC). Diagnosis of a bone lesion is therefore challenging to distinguish its nature in a patient suffering from both diseases. We report the case of a 69-years-old woman referred for P16 positive HPV-HNC. Magnetic Resonance Imaging (MRI) showed T2 hypo-signal on iliac crest and spine. FDG-PET demonstrated radiotracer uptake on these locations suggesting bone metastasis. However, bone biopsy showed epithelioid granuloma without malignant cells compatible with sarcoidosis location. The diagnosis of both localized advanced HPV-HNC and systemic sarcoidosis (bone, central nervous system) were retained. The patient received corticosteroid regimen at 0.5mg/kg/day and Methotrexate for sarcoidosis and radiation and chemotherapy with platins for carcinoma. As granulomatous bone marrow infiltration may have an uptake on FDG-PET, bone sarcoidosis can mimic metastatic disease. In addition, MRI often fails to distinguish sarcoidosis lesions from metastatic lesion in bones. As no reliable imaging test can decipher both diseases, the description of our case reinforces the necessity to perform bone biopsy in a patient suffering from both conditions to expertise the nature of bone lesions.