Role of poorly differentiated cluster in gastric cancer: is it a new prognosis factor?

Poorly differentiated Clusters (PDCs) of tumor cells composed of more than five elements have been recently described in gastrointestinal cancers and correlate with a worse prognosis. Our study aims to investigate PDC occurrence in a series of patients with gastric cancer and correlate it with lymph node status and clinical outcome.

50 patients were included in the study; PDCs count was graduated as G1, G2, and G3 according to Ueno classification (PDCs count at 20× <5, 5-9 and ≥10 respectively). We collected several clinicopathologic variables such as tumor location, pTNM stage, vascular or perineural invasion, and lymph-node ratio for each case.

The presence of PDCs was related to vascular invasion (p < .013) and recurrence event (p < .027). When the population was categorized according to the number of PDCs, a significant correlation was found with the presence of lymph node metastasis (p < .000), the Lymph Node Ratio (p < .002), WHO stage at the diagnosis (p < .000) and vascular invasion (p < .001). At the univariate and multivariate analysis, PDCs were found as an independent risk factor for recurrence (HR 1.94; CI 95% 1.209-3.121; p < .006 and HR 0.401; CI 95% 0.187-0.862; p < .017 respectively). The Kaplan-Meier curves for OS and DFS showed a significant association between PDCs and shorter time to recurrence or survival.

PDC is a strong prognostic factor in gastric cancer, easily detectable, and feasible. As far as we know, this is the first report in Literature of a strong correlation between PDC and survival in patients with operated gastric cancer.