Recent studies have shown that podoplanin overexpression is associated with
lymph node metastasis and poor clinical outcome in several malignant
tumors. To investigate the role of podoplanin in
thymoma, we examined 111
thymomas by immunohistochemistry using
monoclonal antibody D2-40, which recognizes podoplanin. The
tumors consisted of 8 type A, 40 type
AB, 15 type B1, 23 type B2, 15 type B3, and 10 combined
thymomas according to the World Health Organization histological classification system and of 41 stage I, 28 stage II, 16 stage III, 20 stage IVa, and 6 stage IVb
thymomas according to the Masaoka staging system. We have found podoplanin expression in 0 (0%) type A, 4 (10%) type AB, 4 (27%) type B1, 16 (70%) type B2, 10 (67%) type B3, and 7 (70%) combined
thymomas and in 5 (12%) cases of stage I, 7 (25%) of stage II, 11 (69%) of stage III, 12 (60%) of stage IVa, and all (100%) of stage IVb
thymomas. Podoplanin was significantly expressed in B2/B3/combined
thymomas and advanced stage
thymomas (P < .0001). On survival analysis, podoplanin expression was significantly associated with an increased risk of death for the whole group of
thymomas (P = .0002), although it was not identified as an independent prognostic factor in multivariate analysis. The significant survival curve differences of podoplanin expression were also seen for stage III/IVa/IVb
thymomas (P = .0409) and B2/B3/combined
thymomas (P = .0478). In conclusion, D2-40 immunostaining seems to be valuable for predicting the aggressive and metastatic potential of
thymomas and the prognosis of the patients.