Perigastric tumor deposits in primary gastric cancer: implications for patient prognosis and staging.

BACKGROUND: Metastatic nodules in perigastric adipose tissue without evidence of lymph node tissue have been reported in gastric cancers. However, the morphological features and clinical significance of perigastric tumor deposits (TD) have not been clarified in gastric cancers.
METHODS: To demonstrate the clinical implication of perigastric TD, 653 consecutive gastric cancer patients were enrolled and all of their slides were reviewed. Separate tumor nodules in the perigastric fat were classified as perigastric TD and correlated with clinicopathologic features and patient survival.
RESULTS: Perigastric TD were observed in 156 (23.9 %) of 653 patients. Perigastric TD were associated with synchronous distant metastasis (p < 0.001), independently of depth and venous invasion. There was a significant difference between the overall survival of those with and without TD by univariate (p < 0.001) and multivariate (p = 0.001) survival analyses. However, distant metastasis or patient prognosis could not be predicted by the morphologic patterns of the TD (p > 0.05). When TD without lymph node tissue and lymph node metastasis were recorded separately, TD were observed in 13 node-negative patients. The overall survival of node-negative patients with TD was significantly worse than that of node-negative patients without TD (p < 0.001).
CONCLUSIONS: Perigastric TD significantly correlated with distant metastasis and satisfactorily predicted patient outcomes independently of invasion depth, lymph node metastasis, and other clinicopathologic factors. Our findings suggest that perigastric TD should be included in the staging of patients with gastric cancer.