Intra-pancreatic, extra-tumoral perineural invasion (nex). An indicator for the presence of retroperitoneal neural plexus invasion by pancreas carcinoma.

A histopathologic study of 65 resected malignant lesions of the pancreas was done to search for a histologic predictor for the presence of extra-pancreatic neural plexus involvement by carcinoma cells. Extra-pancreatic neural plexus invasion by pancreas carcinoma cells, plx(+), was detected in 28 of 65 cases (43%). plx(+) was not significantly associated with tumor location, tumor size, histologic type, or lymph vessel invasion (ly) by carcinoma cells but was significantly associated with rpe. Plx(+) was also significantly associated with mixed moderate and severe degrees of intra-pancreatic neural invasion (ne2/ne3 group), but not with mixed no and slight degrees (ne0/ne1 group). However, fourteen plx(+) cases were excluded in the ne2/ne3 group; they were found in the ne1 group. Therefore, ne factors appear to have a certain but limited usefulness for the prediction of plx(+). When a perineural invasion by tumor cells was found within the pancreas but outside of the major mass of cancer, it was designated "intra-pancreatic, extra-tumoral perineural invasion (nex)". The presence of nex(+) was found in 37 cases, in which 24 out of the 28 plx(+) cases (85.7%) were included. A statistically significant association was found between plx(+) and nex(+). In particular, 12 out of the 14 plx- positive ne1 cases were nex(+). In ne1 cases, 33.3% (14/42) were plx(+), whereas in ne1 and nex(+) cases, 60% (12/20) were plx(+). There was a statistical significance between these two figures (p less than 0.05). Thus, nex(+) appears to be a useful indicator for plx(+), particularly in ne1 cases.