Immunohistochemical study of Tn, sialosyl-Tn and T antigens in human meningiomas.

Since an aberrant glycosylation associated with abnormal expression of cell surface carbohydrates has been described in many human tumours, we have investigated the expression of simple mucintype carbohydrate antigens (Tn, sialosyl-Tn and T) in 30 formalin-fixed paraffin-embedded surgical specimens of primary meningiomas, subdivided according to the WHO classification as follows: 18 meningotheliomatous, 7 transitional, 2 angiomatous and 3 anaplastic; in addition, 5 meningeal samples taken at autopsy were tested as control. Specific monoclonal antibodies (HB-Tn1, HB-STn1 and HB-T1, Dako) were utilized with ABC method; the percentage of immunostained cells was graded as follows: O (no staining); 1 (> 0 to 5%); 2 (> 5 to 50%); 3 (> 50%). Tn antigen was not expressed in any case. Sialosyl-Tn antigen was demonstrated only in cases of anaplastic meningiomas (score 1-3). The immunoreactivity for T antigen was found in 2 cases of meningotheliomatous (score 1) and in all the anaplastic meningiomas (score 1-2). Negative results were obtained with antisera in the control meningeal samples. Our results thus document a peculiar expression of sialosyl-Tn and T antigens in anaplastic meningiomas, suggesting a block of glycosylation as an immunophenotypic finding of malignant transformation. The sporadic immunostaining for T antigen encountered in the meningotheliomatous variety may be interpreted as an intermediate step of malignant changes.