Extranodal follicular dendritic cell sarcoma/tumours (FDCS/Ts) and interdigitating dendritic cell sarcoma/tumours (IDCS/Ts) are rare neoplasms. We present two cases of FDCS/T and IDCS/T of the breast. The FDCS/T case (case 1) presented in a 31-year-old woman and the IDCS/T case (case 2) in a 67-year-old woman who both showed a firm lump in the left breast. The FDCS/T lesion superficially appeared as an anaplastic carcinoma and the IDCS/T was reminiscent of a spindle cell sarcomatoid carcinoma. Nevertheless both lesions were negative for keratins while case 1 displayed neoplastic cells strongly positive for CD21, vimentin and focally for CD68 and S-100 protein. The tumour cells of case 2 were positive for S-100, CD68 and CD45. In breast, an unusual keratin negative tumour composed predominantly of spindle cells arranged in fascicles, storiform pattern or whorls with a lymphoid rich stroma should raise suspicion for FDCS/Ts or IDCS/Ts. The distinction from malignant tumours with similar features is discussed.