Our findings suggest that clinical guidelines for follow-up strategy should be based on tumor size (>8 cm), initial stage IV disease, microscopic malignant characteristics (LVI, PPI, and WHO malignancy criteria), and high Ki-67 index. The patient presented with recurrent SPN in our case series had a 9 cm tumor with LVI, PPI, and extensive mitosis on histology at the time of the first resection, which was consistent with these criteria. This evidence concerns the gene MKI67 and neoplasm.