Immunohistochemically, the staining results of tumor cells in the small intestine and kidney were consistent; the tumor cells were positive for CD3 (Fig. 3 A), CD56 (Fig. 3B), granzyme B (Fig. 3 C), TIA-1 (Fig. 3D), and perforin (Fig. 3E), while negative for CD4, CD8, CD5, Desmin, CD34, CKpan, CD20 (Fig. 3 F), CD30, SMA, CD79ɑ, and PAX8. Here, PRF1 is linked to neoplasm.