Bone Marrow Involvement by Metastases and Granulomatous Conditions

The bone marrow (BM) can be involved by a variety of non-hematopoietic processes, such as malignancy and granulomatous conditions. Both aspiration and trephine biopsies are valuable in the evaluation of these non-hematopoietic conditions, and bilateral sampling may increase the diagnostic yield in metastatic disease. Almost any malignant tumor has the potential to metastasize to the marrow, including carcinomas, sarcomas, and melanomas. The clinical presentation is nonspecific and peripheral blood findings are variable. Metastatic non-hematopoietic malignancies can sometimes mimic hematologic tumors; by integrating morphology and immunohistochemistry (IHC), the primary origin can often be determined. BM granulomas are an infrequent finding. The differential diagnosis is wide, and clinical findings should direct the majority of the work-up.