TPO and nerve sheath neoplasm: Regarding the immunohistochemistry studies carried out in 13 out of the 14 cases included, our findings confirm that the neoplastic cells are mostly positive for SMA, MSA and vimentin (Fig. 4), without expression of other markers, such as S100 protein, H-Caldesmon or desmin, which allows us to rule out, among others, nerve sheath tumors, smooth muscle, striated muscle and fibroblastic proliferations.