On the other hand, the absence of neural crest stem cells within the tumor, as suggested by negativity to SOX2 [70] as well as the lack of other malignancy features previously associated with MPNST (i.e., necrosis, osteocartilaginous differentiation, high mitotic rate) [28,46,49,50,51,57] and, especially, the lack of fish necropsies, did not allow us to classify the present neoplasms as definitively malignant without any confirmation of metastatic behavior of the neoplasia. Here, SOX2 is linked to malignant peripheral nerve sheath tumor.