Back to Homepage

Case 140 - Discussion

Hematopathology Case

Note: The patient had a recent diagnosis of acute myelomonocytic leukemia, AMl-M4.

Acute myeloid leukemia with nodal involvement (myeloid sarcoma)

Acute myeloid leukemia (AML) with nodal infiltration usually shows a sinusoidal and interfollicular pattern, particularly in the early stage of disease. At lower magnification, the lymph node often has relatively preserved architecture with unusual "pink" staining in the interfollicular regions and sinuses. At higher power view, the cells are medium sized with round or irregular nuclei and open chromatin. Nucleoli may or may not be prominent. The cytoplasm is usually moderate in amount.

     AML with myeloid differentiation often has scattered eosinophilic myelocytes, which have blastic nuclei and bright pink and granular cytoplasm; it is a strong hint for AML with tissue infiltration (myeloid sarcoma). Immunostains for CD34, CD117 and MPO are useful in highlighting the leukemia cells.

    AML with monocytic differentiation can be challenging. The leukemia cells are medium sized with irregular nuclear contours and fine chromatin. There are no eosinophilic myelocytes and the tumor cells are negative for CD34 and MPO. CD45 is often positive, but can be negative; and CD43 is more sensitive than CD45 in labeling the leukemia cells.

    Another hint is that CD3 and CD20 only highlight a small proportion of cells in the interfollicular regions and sinuses despite significant expansion of these areas, indicating an infiltration by non-lymphoid cells.