PMC9779991_01
Bone marrow aspiration at high magnification x100 showing bone marrow infiltration by histiocytic cells. Large histiocytes with hypochromatic nuclei and abundant vacuolated cytoplasm (arrow).
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fig1
It was infiltrated by 31% of large histiocytes with hypochromatic nuclei and abundant vacuolated cytoplasm, without emperipolesis (Figure 1).
Biopsies showing infiltration by histiocytic cells. (a) Cervical lymph node biopsy, hematoxylin, and eosin, x20. (b) Bone biopsy, hematoxylin, and eosin, x10. (c) Bone marrow biopsy, hematoxylin, and eosin, x10.
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An infiltration by mature histiocytic cells was also observed in bone marrow, lymph nodes, and bone biopsies (Figure 2).
Immunohistochemical staining of lymph node biopsy. (a) CD68 expression by histiocytic cells. (b) S100 protein expression by histiocytic cells. (c) Histiocytic cells lack CD1a expression.
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Immunohistochemically, the histiocytes were positive for CD68 and S100 protein but negative for CD1a (Figure 3).