PMC9339126_01
Bone marrow aspirate (A, B) and biopsy (C, D) showing infiltration by atypical lymphoid cells, which are positive for CD3 on IHC (D, inset) [Leishman, (A) 400X & (B) Oil immersion; H & E (C) 400X; IHC (D) 200X, (inset) 400X].
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F1
Some of these cells resembled blasts, thus arousing a dilemma between acute leukemia or lymphoma infiltration [Figure 1]. IHC demonstrated positivity of the infiltrating lymphoid cells for CD 3 and negativity for CD 20, CD 34 and TdT, thus confirming involvement by a mature/peripheral T cell lymphoma [Figure 1].
Flow cytometric analysis exhibiting predominance of the lymphoid population which was gated on the CD45 vs Side Scatter plot. The gated events demonstrate positivity for cytoplasmic CD3, surface CD3, CD8, CD7 and CD56, while negativity for MPO, CD4, CD34, CD20, TdT, CD10, CD5 and CD19 (not shown).
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F2
NHL infiltrating the marrow, with the possibility of HSTCL, in light of the clinical and the radiological findings. Negativity of the atypical cells for TdT and CD 34 and positivity for surface CD 3 did not favor a leukemic disease [Figure 2]. 
Liver biopsy (A, B, C) and splenic FNAC (D) revealing sinusoidal infiltration by atypical lymphoid cells. IHC on the liver biopsy demonstrates reactivity of the cells for CD3 [H & E, (A) 200X (B) 400X; IHC (C) 200X; MGG (D) 400X].
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F3
Trucut biopsy from the liver revealed distinctive sinusoidal dilatation as well as infiltration by abnormal T lymphoid cells as identified by CD 3 on IHC; CD 1a was negative [Figure 3].