Lymphatics and D2-40/podoplanin expression in gastrointestinal stromal tumours of the stomach with and without lymph node metastasis: an immunohistochemical study with special reference to the Carney triad

Background Lymph node metastasis of gastric gastrointestinal stromal tumours (GISTs) in children and young adults, especially those with the Carney triad, is common (similar to 29%) and contrasts with that of sporadic gastric GISTs (<= 2%). The mechanism responsible for this difference in tumour behaviour is not understood. In previous studies, expression of the lymphatic endothelial marker D2-40/podoplanin in carcinoma cells and the presence of intratumoural/peritumoural lymphatics have been correlated with tumour invasiveness and nodal metastasis. Methods This study investigated the presence of intratumoural and peritumoural lymphatics, and expression of D2-40/podoplanin, in 16 patients with syndromic/paediatric gastric GISTs (11 patients had Carney triad, two had Carney-Stratakis syndrome and three had paediatric GISTs suspicious for the Carney triad) with histologically verified metastasis to regional lymph nodes. The results were compared with those found in 35 sporadic gastric GISTs lacking nodal spread using the antibody D2-40/podoplanin. Results The mean ages at GIST diagnosis in the patients with syndromic/paediatric GISTs and those with sporadic GISTs were 18 years and 67 years, respectively. Intratumoural lymphatics were detected with comparable frequency in the two tumour sets (25% and 17%, respectively; p = 0.705). Peritumoural lymphatics were equally present in the tumours from both of the groups. Moderate/strong cytoplasmic/membranous staining for D2-40/podoplanin was frequent in the neoplastic cells of syndromic/paediatric GISTs (87%), and infrequent in sporadic GISTs (3%) (p<0.001). Conclusion The results indicate that intratumoural lymphangiogenesis is probably not involved in lymphatic spread in syndromic/paediatric GISTs. The biological significance of D2-40/podoplanin expression in tumour cells of syndromic/paediatric GISTs and its possible role in lymphatic tumour spread remain to be further investigated.