The primary ACP11 tumour showed classic features of ACP (palisading epithelia, wet keratin, epithelial whorls), however, histological analysis of this patient’s second recurrence revealed the presence of malignant features, including: (1) Poorly differentiated solid epithelial tumour composed of a mixture of solid nests, tubules and thin trabeculae infiltrating the stroma; (2) Frequent mitotic Figures (12/mm2); (3) KI67 positivity in the majority of the tumour cells (Fig. 3A). The gene discussed is MKI67; the disease is neoplasm.