Histological benign lesion can be fatal if

CharacteristicsBenignMalignantDifferentiation Well differentiated; structure may be typical of tissue of origin Some lack of differentiation with anaplasia; structure is often atypicalRate of growth Usually progressive & slow; may come to a standstill or regress; mitotic figures are rare & normal Erratic & may be slow to rapid; mitotic figures may be numerous & abnormal Local invasion Usually cohesive & expansile well-demarcated masses that do not invade or infiltrate surrounding normal tissuesLocally invasive, infiltrating the surrounding normal tissues; sometimes may be seemingly cohesive & expansile Metastasis Absent Present; the larger and more differentiated the primary , the more likely are metastases