Follicular lymphoma cells (dark purple), illustration. Lymphomas are malignant (cancerous) growths of white blood cells (lymphocytes). White blood cells are part of the bodys immune system and circulate in a clear liquid called lymph. Follicular lymphoma is a slow-growing non-Hodgkins lymphoma of the B lymphocytes, or B cells, where the cells form clusters, or follicles. It accounts for around 20 per cent of all non-Hodgkins lymphomas.