The luminescent semiconductor quantum dots (QDs) are a promising class of materials for labelling of biological systems. One class of targeting biomolecules that is commonly used conjugated to QFs are lectins. These molecules are structurally diverse carbohydrate-binding molecules proteins of non-immune origin that agglutinate cells. Con A conjugated to CdS/Cd(OH)₂ quantum dots (QDs) were used to investigate cell alterations regarding carbohydrate profile in human mammary tissues diagnosed as fibroadenoma (benign tumour). QDs were funcionalized with glutaraldehyde and conjugated to Con-A. Fibroadenoma tissue sections (4mm) were deparaffinized, hydrated in graded alcohol, treated with trypsin and Evans Blue solutions and submitted to lectin histochemistry. Confocal microscopy was used for fluorescence evaluation. QD-Con A fluorescence intensity in stained tissues showed different patterns, which reflect the carbohydrate expression of glucose/mannose in fibroadenoma when compared to the detection obtained in normal tissues. Unspecific labeling pattern of tissues with glutaraldehyde functionalized CdS/Cd(OH)₂ quantum dots was different to that observed to the targeting driven by the Con-A lectin. The preliminary findings reported here support the use of CdS/Cd(OH)₂ quantum dots conjugated to Con A as specific probes for cellular alterations and their use in diagnostics.