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Case 43 - Discussion

Hematopathology Case


CK AE1/3


Vimentin S100

CD45 CD45


CD8 CD79a
CD20 CD21

CD31 CD35
CD43 CD43



CD68 CD68
CD15 CD15

Myeloid Sarcoma Involving Lymph Node

  • The lymph node architecture is effaced by diffuse infiltration of medium- to large-sized tumor cells. They have irregular nuclei with open chromatin and one or several small nucleoli. The cytoplasm is moderate in amount and pale basophilic with frequent vacuoles but no other inclusions.

  • By immunostaining, the tumor cells are positive for CD43, CD45 and myelomonocytic markers (CD15, partial CD68, and lysozyme), and are negative for CD3 and CD20.

  • Myeloid sarcoma involving lymph node can be difficult to recognize. The tumor typically have interfollicular and sinusoid infiltrating pattern with relatively preserved nodal architecture. At low power, the interfollicular areas may look "pinkish". At high power, the tumor cells are usually medium sized with round or irregular nuclei. The chromatin is usually fine and nucleoli may be prominent. For myeloid sarcoma with myeloid differentiation, precursor eosinophils (particularly eosinophilic myelocytes) are often present, although they may be scattered, which is a very helpful hint; for myeloid sarcoma with monocytic differentiation, the tumor cells are often more irregular, and immature eosinophils are absent. Tumor cells typically express myeloid or monocytic marker. CD43 is a very sensitive marker to highlight myeloid neoplasms of various differentiation.

  • The major differential diagnosis includes large B-cell lymphoma, anaplastic/blastoid mantle cell lymphoma, anaplastic large cell lymphoma of null cell type. Immunostains can easily distinguish these lymphomas from myeloid sarcoma.