Plasma cell leukemia (PCL) is a rare and aggressive plasma cell neoplasm that may either originate de novo (primary PCL) or by leukemic transformation of multiple myeloma (MM) to secondary PCL (sPCL). It is defined by the presence of >2 G/L plasma cells or >20% plasmacytosis of the differential white cell count in the peripheral blood. In this case series, we describe the clinicopathologic, biologic and immunophenotypic, of four patients diagnosed with PCL within a four years period (2013-2016) at CHU Hassan II, Fès, Morocco.