Plexiform structures in peripheral nerve sheath tumors (PNST) after prenatal and postnatal exposure to Ethylnitrosourea (ENU)

Two groups of 20 female Wistar rats received a single i.p. injection of RNU (15 mg/kg b.w.) on the 15th day (group I) and 21st day (group II) of pregnancy. Their effective progeny amounted to 180 descendants (95 m, 85 f) for group I and 172 descendants (93 m, 79 f) for group II.In addition, group III , composed of 81 m and 76 f, descendants of another set of 20 pregnant Wistar rats received a single s.c. injetion of ENU (15mg/kg b.w.) on the first postnatal day. PNST, most of them histologicaly malignant, deveoped in the animals according to the following numbers. Group I: 64 (36%), group II 130 (76%) and group III 80 (56%). No PNST were observed neither in group IV composed of 156 controls (78m, 78 f) nor in the mothers of all groups. In group I, 19 out of 64 PNST (30%) showed plexiform structure, in group II, they were seen in 27 out of 130 PNST (21%), and in group III in 14 out of 88 PNST (16%). Comparing the incidence of plexifom structures between PNST of the three groups, there w as a value p<0.05 for group I when compared with group III. Other comparisons were not statistically significant. Since when seen in man, even if it is the sole manifestation, these plexiform structures are considered to be distinctive of neurofimonatosis, it is suggested that the present experiments may offer a model for studying this diseases, particularly its association with malignant changes, as well as some aspects related to differences between its forms.