Use of Sialic Acid as a Complementary Method in the Cytological Diagnosis: Preliminary Study

INTRODUCTION: Cellular morphology does not allow, in many cases, to safely establish a diagnosis of malignancy or benignity. Sialic acid is found in the membranes of well-differentiated mature cells, normally located in the alpha-2,3 position. During tumor progression, changes occur in glycosylation of proteins and lipids, including alterations in the sialylation patterns of tumor cells. OBJECTIVE: To confirm the overexpression of alpha-2,6 sialinization in exfoliated cells of body fluids and bronchoalveolar lavage (BAL) as a malignant indicator mechanism, using glycan-binding lectins. MATERIALS AND METHODS: Thirty samples (20 effusion liquids and 10 BAL) diagnosed by Giemsa and Papanicolaou staining as negative and positive for malignancy, were studied. They were then stained with fluorescein-labeled Sambucus nigra lectin (Sigma Chemicals, USA), which specifically recognizes sialic acid in alpha-2,6 position. The fluorescence obtained at 515 nm evidenced the presence of sialic acid in the 2,6 position. RESULTS: Negative body fluids for malignancy showed a fine and homogeneous fluorescence pattern for reactive mesothelial cells. Neoplastic cells revealed a thick, heterogeneous pattern. In BAL, benign hyperplastic cells showed a homogeneous fine pattern while neoplastic cells showed a thick and heterogeneous fluorescence pattern. The pattern described was observed in all cases in the cell membrane. CONCLUSION: It was observed that the change in sialic acid conformation detected through Sambucus nigra Lectin could be used as a complementary method for the diagnosis of malignancy in different cytological samples.