MPO and neoplasm: Immunohistochemical analysis revealed that the atypical tumour cells were positive for CD3 (Figure 2A), TCR-βF1, CD4 (Figure 2B), CD5, CD7, CD25, cytotoxicity-related protein TIA-1 (Figure 2C) and granzyme B, but were negative for TCR-CγM1, CD8, Foxp3, CD15, CD20, CD79a, CD30, ALK-1, CD56, CD57, TdT, myeloperoxidase, lysozyme, EMA and cytokeratin AE1/AE3.