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[Histological diagnosis of regional lymph node micrometastasis with or without stromal reaction in gastric carcinoma].

OBJECTIVE
To define lymph node micrometastasis and to investigate the difference between micrometastasis and microinvolvement.


METHODS
A total of 1,087 regional lymph nodes were collected from surgical specimens of 17 patients with gastric carcinoma. 71 nodes were found to contain microlesions, <or= 0.5 mm or <or=50 tumor cells per node by serial sections (> 60 sections per node) and immunohistochemistical staining for CK18, EMA and SAM. Another 20 nodes containing macrometastasis were also studied.


RESULTS
After serial sections, the microlesions disappeared in 34% (24 nodes), increased in 49% (35 nodes), microlesions transformed into macrometastasis in 17% (12 nodes). Microlesions presented as a cluster of tumor cells (<or= 0.5 mm) or scattered single cells (<or= 50 cells). Stromal reactions surrounding the clustered tumor cells were found in 50.0% of nodes while stromal reactions surrounding scattered cells were found in 10.5% of nodes. There was no consistent stromal reaction either in nodes with micrometastasis or nodes with macrometastasis, not even within a same node. Stromal reaction was more often found in the higher differentiated group.


CONCLUSION
(1) A few sections per node cannot define the nodal micrometastasis and nodal macrometastasis may be misjudged as micrometastasis without serial sections, leading to undestaging of pN. (2) The use of stromal reaction to differentiate nodal micrometastasis from nodal microinvolvement, as suggested by Siewert, is not substantiated.