Background and methods: A 63-year-old woman was transferred to our institution with suspected metastatic renal cell carcinoma (mRCC). Biopsies of the kidney and hepatic lesions proved partly sarcomatoid-differentiated clear cell carcinoma. Initially presenting with fever of unknown origin, the patient was empirically treated with antibiotics, but the patient's condition deteriorated and she developed progressive severe thrombocytopenia followed by mild anemia. Several blood tests were done to identify the cause of the thrombocytopenia.
Results: Radiologic imaging and clinical presentation showed rapidly progressive mRCC. Clinical and laboratory features were incompatible with severe sepsis, thrombotic thrombocytopenic purpura (TTP) or idiopathic thrombocytopenic purpura (ITP) and laboratory tests were negative for heparin-induced thrombocytopenia (HIT). The patient's current medication was changed to exclude potential drug-induced thrombocytopenia and the bone marrow was biopsied. The results showed massive bone marrow infiltration of RCC.
Conclusions: Although very rare, bone marrow carcinosis can occur in patients with mRCC and may present a diagnostic challenge. It is associated with a very poor prognosis.