Histopathological effect of radiofrequency ablation therapy for primary breast cancer, with special reference to changes in cancer cells and stromal structure and a comparison with enzyme histochemistry

Radiofrequency ablation (RFA) therapy is expected to be applicable to small breast cancers, but no criteria for its histopathological effect have yet been established. Using samples obtained from 15 patients who had undergone RFA and subsequent mastectomy, we compared the histopathological changes in the ablated area with the results of histochemical staining based on the reduction of nitroblue tetrazolium chloride (NBT) by nicotinamide adenine dinucleotide (NADH) diaphorase in frozen tissue sections, and looked for histological changes indicative of the effect of RFA on breast cancer. Grossly, the ablated area in most of the tumors was rough, gritty, less moist, and surrounded by a red congestive limbic zone. The ablated area showed no staining by the NADH diaphorase reaction, and cancer cells in the area showed marked destruction characterized by an unclear intercellular boundary, elongated eosinophilic cytoplasm, pyknotic “streaming” nuclei, and a poorly defined nuclear and cytoplasmic texture. At the same time, fibrous connective tissue also showed degenerative changes, becoming densely homogeneous with loss of its delicate wavy structure. The area in which RFA appeared to have been histopathologically effective was mostly concordant with the area in which the NADH diaphorase reaction was negative. In the periphery of the ablated area, however, cellular changes caused by RFA were less marked, although the NADH diaphorase reaction was visualized with NBT. A larger number of cases should be examined in order to establish criteria for the histopathological effect of RFA on breast cancer.