Detection of alterations in chromosomes 16 and 1 by fluorescence in situ hybridization in breast tumors cytologically or histologically equivocal for malignancy.

Structural and numerical alterations, and fusion of chromosomes 16 and 1 have been shown to occur frequently in low-grade breast carcinoma, but not in benign papilloma by fluorescence in situ hybridization (FISH). We carried out FISH analysis of 11 benign tumors and 3 breast tumors for which the preoperative diagnosis was equivocal for cancer. In 11 benign lesions and 1 benign phyllode tumor which was cytologically equivocal for malignancy, alteration of the chromosome 16 or 1 signal was not detected as a predominant cell clone. On the other hand, in 1 grade 1 invasive ductal carcinoma which was judged as equivocal for malignancy and 1 marked adenosis with atypia which was judged as malignant by fine-needle aspiration cytology, the majority of constituent tumor cells showed fusion of chromosomes 16 and 1. Detection of alterations in chromosomes 16 and 1 as a predominant clone was suggested to be an indicator of lesion malignancy even though the grade of malignancy may not be high. As a supportive diagnostic procedure, FISH analysis may give information about the nature of lesions, when the lesions are clinically or pathologically equivocal for cancer.