This is a prospective single-center study designed to assess potential differences in cell composition between bone marrows of patients with follicular lymphoma and those from control subjects. Follicular lymphoma is the most common indolent lymphoma. It is characterised by systematic relapses and bone marrow dissemination in 70% of patients at the time of diagnosis. Although relapses are thought to be related to refractory tumour cells nested in a supportive microenvironment in the bone marrow, the mechanisms involved are poorly understood. To study the specificities of the bone marrow of patients with follicular lymphoma, It is necessary to compare them with control samples. This study takes advantage of surgeries involving sternotomies to recover lost bone marrow and establish a bone marrow bank of patients without hematological disease. This bank will be used to set up control cohorts for other clinical trials involving patients with follicular lymphoma.