Next, we related PlGF transcript levels to morphologic features of more advanced ET-NI, such as a wide circumferential range of perineural tumor cell invasion along the sheath of nerves (referred to as perineural invasion; PNI), and tumor cell invasion within the intraneural space of nerves, referred to as intraneural invasion (INI; illustrated in Fig. 4A and B). The gene discussed is PGF; the disease is neoplasm.