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294 OCCUPATIONAL TUMORS AND ALLIED DISEASES races. DeBell and Stevenson mentioned the presence of a burn scar cancer in a Negro, Treves and Pack saw one in a Negress, and Vaughan made similar observations in Chinese. Age. The age distribution of 49 cases collected from the literature is presented in the following table. AGE DISTRIBUTION OF BURN SCAR CARCINOMA Years Cases 20-30 31-40 41-50 51-60 61-70 71-80 81-90 4 7 21 6 7 2 1 Total 49 The average age of this series is 48 years, which agrees with the age group in which the peak of the age incidence occurs. Arndt reported an average of 47 years for chronic burn scar cases and of 48 years for acute burn scar cases. Mason gave a slightly higher figure of 51.5 years for burn scar cancers in general, while Treves and Pack noted an average age of 53.5 years for the chronic cases and of 56 years for the acute cases. These discrepancies in the average age of burn scar cancers are probably only apparent ones and are caused by the type of material analyzed. Inas much as Treves and Pack pointed out that not the absolute age of the individual, but the age of the scar is the decisive factor determining the development of malignant transformations (Johnson), it is obvious that burns sustained during childhood are apt to result in cancer at a con siderably earlier, age than thermic injuries suffered during adult life, possibly in the form of occupational accidents. The youngest individual with burn scar cancer, observed by Treves and Pack, was 14 years old and had been burned, at the age of 3.5 years. An analysis concerning the average age, based on a series containing an appreciable number of burns sustained during child hood, should yield a lower age figure than that obtained from an evaluation of a series composed mainly of industrial burns. Latency Period. The length of the latency period varies greatly, ranging from a few weeks to many years. Acute burn scar cancers which develop on the basis of a primary persistent ulcerative defect or within a very young scar have a latency period of a few weeks to several months. Treves and Pack gave an average latency period for acute burn scar cancers of 4 months. Stauffer reported the development of a carcinoma from a burn ulcer in a man, 66 years old, after a 4 weeks interval. A similar observation was made by MacLeod. Cornil and Lamy noted in a man, 26 years old, a malignant development from a thermic ulcerative defect after an elapse of 5 months, while Pickerill recorded the appearance of a cancer within the same period in a man, 45 years old, under similar circumstances. A somewhat longer interval, 2 years, was noted by Pickerill in a second case involving a man 43 years of age. Haagensen listed in one instance an interval of 18 months, the patient being 57 years old. It seems to be characteristic of this group of acute burn scar cancers that the