"Crawling-type" adenocarcinoma of the stomach: a distinct entity preceding poorly differentiated adenocarcinoma

Gastric "crawling-type" adenocarcinoma (CTAC) is a neoplasm histologically comprising irregularly fused glands with low-grade cellular atypia that tends to spread laterally in the mucosa. It is necessary to elucidate the clinicopathological characteristics of CTAC. We evaluated 25 CTACs-16 intramucosal (M-) and 9 submucosal invasive (SM-) cancers-clinicopathologically and immunohistochemically. CTAC was most frequently located in the lesser curvature of the middle-third of the stomach. Macroscopically, 21 lesions were superficial-depressed and 4 were superficial-flat type. Histologically, all CTACs had cystic dilated glands and 16 lesions had focal signet-ring cells. All invasive areas of the SM-CTACs were occupied by poorly differentiated adenocarcinoma with an infiltrative growth pattern and abundant stroma. Fifteen CTACs were surrounded by mucosa with partial or no intestinal metaplasia. In the intramucosal area, 24 lesions were mixed phenotype with mucin and brush border immunoexpression. SM-CTAC was frequent in lesions with an intramucosal poorly differentiated component (PDC) greater than 10 mm in size (P = 0.041), and lymph node metastasis (LNM) was frequent in lesions with a PDC greater than 20 mm (P = 0.039). The frequency of an expanded pattern (Ki-67-positive cells occupying > 50 % of the mucosa) was higher in SM-CTAC than in M-CTAC (P = 0.027). p53 overexpression was not detected in the intramucosal areas of any of the lesions. CTAC is a distinct subgroup of gastric adenocarcinoma in the early phase. A larger PDC and a Ki-67 expanded pattern were predictive of submucosal invasion or LNM.