Skin cancer in chronic arsenicism

Abstract

In a limited area on the southwest coast of Taiwan where artesian well water with a high concentration of arsenic has been used for more than 50 years, a high prevalence of chronic arsenicism has been observed in recent years. The total population of this endemic area is approximately 100,000. A general survey of 40,421 inhabitants of the area was made (19,269 males and 21,152 females). The overall prevalence rates for skin cancer, hyperpigmentation, and keratosis were 10.6, 183.5, and 71.0 per 1000, respectively, and for blackfoot disease (a local term), a peripheral vascular disorder resulting in gangrene of the extremities, especially the feet, 8.9 per 1000. The male-to-female ratio was 2.91:1 for skin cancer, 1.1:1 for hyperpigmentation and keratosis, respectively, and 1.99:1 for blackfoot disease. Generally speaking, the prevalence increased steadily with age in all four conditions. The association of blackfoot disease with hyperpigmentation, keratosis, and skin cancer was significantly higher than expected. The causal relationship between blackfoot disease and chronic arsenicism is emphasized. A total of 303 arsenical cancers in 184 patients (119 men and 65 women) were studied histologically; 143 patients (78 per cent) were older than 50 years. Of the 303 lesions, 57 were epidermoid carcinoma, 45 basal cell carcinoma (28 deep and 17 superficial), 176 intraepidermal carcinoma (23 type B keratosis and 153 classic Bowen lesions and its variants), and 25 combined forms. Bowen's variants included 10 with squamous whirls, seven with features of seborrheic keratosis, and 12 with horn formation. The combined forms were a mixture of superficial basal cell carcinoma, Bowen's lesion or its variants, and Jadassohn epithelioma. Among the 45 basal cell carcinomas, 10 revealed bizarre multinucleated giant cells and nuclear atypicalities, three in deep and seven in superficial layers. The cases of arsenical keratosis encountered were of both benign type A and malignant type B (intraepidermal carcinoma) forms. Among the 81 type A keratoses, 57 revealed no cellular atypy and 24, only mild changes. The fine structure in 30 classic cases of Bowen's lesion is briefly described and illustrated. A five year follow-up study of 422 skin cancer patients and 344 patients with blackfoot disease was made. Standard mortality ratios were calculated for both and the causes of death analyzed.