Mantle cell lymphoma (MCL) in a cervical lymph node (higher magnification of the previous image). The tumor 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. Histiocytes with pink cytoplasm are scattered in the background. Mitotic figures are readily seen. Some MCLs are composed predominantly of small lymphocytes with round nuclei lacking indentations or clefts. Such cases may closely resemble chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). However, MCLs lack proliferation centers as well as paraimmunoblasts and prolymphocytes. In addition, MCL is usually CD23-ve where as CLL/SLL is usually positive for this marker.