Mantle cell lymphoma, light micrograph. Mantle cell lymphoma involving the kidney in a middle-aged male. The tumour consists of a uniform population of small to medium sized lymphoid cells resembling centrocytes with irregular, indented or clefted nuclear contours. The cells have condensed nuclear chromatin, inconspicuous nucleoli, and a thin rim of cytoplasm. Larger transformed cells such as centroblasts, paraimmunoblasts, and prolymphocytes are absent.