Histological changes in human breast cancer after interstitial irradiation with a pulsed Nd-YAG laser

This is a clinical study of the histological changes induced in human primary breast cancer by single-session pre-operative interstitial irradiation using a medium-power Nd-YAG laser (1064 nm, 1–6 W, 20 pulse s-1, 100 Μs). Changes were studied in 15 tumours resected at an interval of 1–11 days after laser treatment, and in four biopsy samples from three tumours treated conservatively and biopsied for suspected recurrence 1–3 months after laser treatment. All foci of laser-induced destruction consisted of a sphere-shaped infarction 0.5–2.5 cm in diameter which enclosed a small evaporation cavity within carbonized walls. Vapour separation occurred in two tumours and gaseous rupture was seen in one tumour. Extensive vascular damage was seen inside the damaged area; damage to cancer cells was manifested by diminished size, vacuolization, cytoplasmic turbidity, pyknosis, disruption of the nuclear membrane and nuclear homogeneity. No clear morphological signs of damage could be seen in a significant percentage of cancer cells on short-term inspection (35–80%). Long-term histological study revealed a central necrotic area of diameter 1–1.2 cm in the laser-treated tumours, containing no viable cancer cells. In inadequately treated carcinomas, regrowth of tumour was seen at the periphery of this zone.