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Case 79 - Discussion

Uploaded: 2009-06-24, Updated: 2009-07-12

 

 

CD20

CD20

CD3

CD3

CD4

CD4

CD8

CD8

CD31

CD31

CD34

CD34

MPO

Lysozyme

Ki67 Ki67
   

Diagnosis: myeloid sarcoma of lymph node.

 

Microscopic description:

The architecture of the lymph node is almost entirely effaced by a diffuse paracortical, perisinusoidal and sinusoidal proliferation of medium-size mononuclear cells with irregular nuclear contours, often finely dispersed chromatin, one to multiples small nucleoli, and ill-defined cytoplasmic borders, admixed with scattered eosinophilic precursors as well as apparent mature eosinophils, small lymphocytes, histiocytes, and plasma cells. There are increased numbers of small thick-walled blood vessels.  A few secondary lymphoid follicles are noted. The sinuses are dilated and filled with apparent histiocytes. 

       

 The CD45 stain highlights numerous positive cells. Numerous variably-sized T-cells are seen on the CD2, CD3, CD5, CD7 and CD43 stains. Weakly staining mononuclear cells are also noted in the interfollicular areas on the CD5 stain; on the CD7 stain, these cells are intensely positive. Moderately numerous CD8 positive lymphoid cells are seen; many fewer CD4 positive lymphoid cells as well as histiocytes are seen. Moderately numerous scattered positive cells are seen on the granzyme B and TIA-l immunostains. Ki-67 stain shows moderate numbers of positive nuclei. There are very few scattered CD57positive cells. Moderately numerous mononuclear cells in the paracortical areas are positive for CD34 and TdT. CD56 stain highlights clusters of apparent immature myeloid elements, particularly in the sinuses, and possibly plasma cells. Many but not all of the interfollicular mononuclear cells are positive for lysozyme and myeloperoxidase (of variable intensity); many of the lysozyme positive cells show perinuclear dot-like pattern of positivity. CD21 stain highlights irregular, ill-defined meshworks of follicular dendritic cells, often associated with B-cell rich areas. In situ hybridization stain for Epstein-Barr virus encoded RNA (EBER) shows few scattered positive cells.

       

 The histologic sections, together with the immunohistochemical stains described above, shows nodal involvement by an immature myeloid neoplasm expressing CD34, TdT, myeloperoxidase, lysozyme (at least partially), CD7, CD56 (partially), and possibly CD5. These findings would be consistent with the diagnosis of myeloid sarcoma by WHO criteria. This may occur de novo or concurrently with an acute myeloid leukemia or occur in the setting of an underlying myelodysplastic syndrome or chronic myeloproliferative or myelodysplastic/myeloproliferative disease. Clinical correlation including evaluation or peripheral blood and bone marrow, is required for full evaluation.

 

Peripheral blood smear and bone marrow biopsy were evaluated and described in hematopathology case 81.