Patterns of ice formation in normal and malignant breast tissue.

Normal and malignant human breast tissues were obtained from resection surgery and frozen on a directional solidification stage with controlled and uniform cooling rates. The frozen samples were freeze substituted and examined with a light microscope. It was observed that in both normal and malignant tissue, ice forms first in the connective tissue. The ice propagates along the connective tissue, which surrounds fat cells in normal adipose tissue and clumps of tightly packed malignant cells in the diseased tissue. This mode of freezing affects the osmotic response of malignant cells, causing intracellular ice crystal formation at unusually low cooling rates.