Skeletal sarcoidosis; an uncommon mimic of metastatic disease

A 66-year-old man with pulmonary sarcoidosis was referred to the urology team for assessment of troublesome lower urinary tract symptoms. An elevated blood serum prostate-specific antigen raised concern for prostate cancer. An MRI of the prostate demonstrated a potentially aggressive prostate lesion, along with low T1 signal skeletal lesions, suggestive of metastatic disease. Subsequent bone scan and MRI whole spine demonstrated further skeletal lesions. In cases of known prostate cancer, sometimes a presumptive diagnosis of skeletal metastases is made without histological diagnosis from the skeletal lesions. However, there were certain factors in this case whereby skeletal biopsy was deemed prudent prior to further therapy. Factors included atypical MRI signal characteristics for metastatic disease, absence of a positive tissue diagnosis from the prostate and the clinical background of sarcoidosis. The biopsy confirmed skeletal sarcoid rather than metastatic disease, thereby avoiding inappropriate and potentially toxic treatment for the patient.