PET positivity with bone marrow biopsy revealing sarcoidosis in a patient in whom bone marrow metastases had been suspected

Abstract

A 71-year-old man with recurrent pneumonia was diagnosed as having a well-differentiated carcinoid tumour and underwent lung lobectomy in February 2007. One month later he developed acute renal failure due to severe hypercalcaemia in the presence of low serum parathyroid hormone concentration. In July 2007 a fluorodeoxyglucose positron emission tomography (FDG-PET) scan, performed for tumour follow up (left), showed increased uptake in vertebrae and also in the femurs (where uptake was evident only in the medullary cavity and not in the cortex); bone scintigraphy was negative. The patient complained of asthenia and was found to have a mild normocytic anaemia and moderate leucopenia. Islets of apparently non-haemopoietic cells were found in a bone marrow aspirate, which raised the suspicion of carcinomatosis; however, bone marrow biopsy unexpectedly revealed the presence of sarcoid granulomas associated with reduction of normal haemopoietic tissue (right). Serum angiotensinconverting enzyme (ACE) concentration was twice normal levels. Corticosteroid therapy was initiated, with rapid improvement of both the clinical condition and the blood abnormalities. Bone marrow involvement in sarcoidosis is uncommon; it may lead to anaemia and leucopenia. The high serum ACE level and the improvement after corticosteroid therapy suggest that the granulomas were not a tumour-related sarcoid reaction, but a primary disease; indeed, several cases showing an association of sarcoidosis with carcinoid tumour, although in different anatomical sites, have been described. It is known that sarcoidosis is often intensely hypermetabolic in FDG-PET images and thus it may complicate the diagnosis of metastatic neoplastic disease.