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I I I I I I I I I I I I I I I I I I PROGRESSIVE CHANGES IN THE RELATIVE DISTRIBUTION OF DIFFERENT HISTOLOGICAL TYPES OF LUNG CANCER IN GUANGZHOU, CHINA Li Lie, Huang Shu-wei, Lu Zhen jie and Wan Guang-ai Department of Pathology, Guangzhou Medical College, Guangzhou, China Abstract A total of 1,048 lung cancer cases obtained from the First Affiliated Hospital of Guangzhou Medical College from 1978 to 1994 were reviewed in this paper. According to WHO's lung cancer classification, the proportion of squamous cell carcinoma (SCC) was 54.68%, for adenocarcinoma 32.44%, for small cell carcinoma 5.15 %, and for large cell carcinoma 1.91 %. These data on SCC and adenocarcinoma were compared to those in a former paper(1). In this comparative study, the total lung cancer cases were nearly the same. When the total number of cases collected in the 16-year period was grouped into three sub-periods (1978 to 1984, 1985 to 1989 and 1990 to 1994) and then analyzed, the percentage of SCC for the three sub-periods was 68.72 %, 57.99 % and 38.8 % respectively. On the other hand, the percentage of adenocarcinoma was 19.43%, 29.1% and 47.49%, for the same three sub- periods. These results showed that the rate of SCC decreased progressively during the past two decades while that of adenocarcinoma increased markedly and even surpassed the rate of SCC. There are statistically significant differences with regard to trend changes in both carcinoma types during the sub- periods (P <0.05 for SSC and P<0.005 for adenocarcinoma), thus confirming the assumption that there is a trend towards an increase of adenocarcinoma in the 16-year period. The increase of adenocarcinoma appears to be due to multiple contributing factors. Future studies of longer duration are needed to help to elucidate the relative role of these factors. Introduction Pathological studies are central to lung cancer research since they provide information on the etiology, prevention, and cure of lung cancer. In this report, the WHO's 1981 criteria for lung cancer histological classification was used to analyze 1048 lung cancer cases collected from 1978 to 1994. A progressive change in the relative distribution of squamous cell carcinoma and adenocarcinoma was observed over the 16-year period. Materials and Methods A total 1,060 lung cancer specimens, obtained by biopsy and during surgery, were collected in the First Affiliated Hospital of Guangzhou Medical College from 1978 to 1994. Based on the histological classification of lung malignant epithelial tumors issued by WHO in 1981, 1048 cases were classified and compared to data presented in a former paper (1). Twelve cases (including a carcinoid tumor, malignant lymphoma and adenoid cystadenocarcinoma) were excluded in the statistical analysis. The data collected in the 16 years, from 1978 to 1994, was grouped into 3 sub-periods - the first sub-period from 1978 to 1984 the second from 1985 to 1990 and the third from 1990 to 1994 - and then analyzed by sub-period. I

I I Results In the total of 1048 cases there were 573 squamous cell carcinomas (54.68%), 340 adenocarcinomas (32.44%), 54 small cell carcinomas (5.15%) and 20 large cell carcinomas (1.91%). The remaining 61 cases were adenosquamous carcinomas (5.82%). The histological types and their rates during different sub-periods are shown in Table 1. Table 1. Hlstologicaltypes of 1048 lung cancer cases and their rates during different sub-periods S-3teaciod/Cc 3Vc l97@-1?%4 19B0-I494~~ ~ .ToL4 ~ SquammrCeBM1+~.+ai-•• 145 (68.72%) 312 (57.99%) 116 (38.8%) 573 SvvaCellCaremom. 16 (7.58%) 25 (4.65%) 13 (4.34%) 54 Admoc.xmoma 41 (19.43%) 157 (29.18%) 142 (47.49%) 340 LuseCeU r•-...:..-. 9 (4.26%) 6 (1.12%) 5 (1.67%) 2U Mmo.qu.moueCucmoma 38 (7.06%) 23 (7.69%) 61 TnW 211 538 299 1048 The rates of squamous cell carcinoma and adenocarcinoma in the 1048 cases on the above table are similar to a previous publication (1). The rate of adenosquamous carcinoma, however, appears to have increased. The data in Table 1 are graphically illustrated below. M J00 80 60 40 20 a 19'/8-1084 1985-1990 1900 t99G - Squamous Cell CarcSnoma --AdBnoeareinuma As shown above, during the last 16 years squamous cell carcinoma, in proportion to the total lung cancers, has been decreasing progressively. The rate of adenocarcinoma, however, has markedly increased. A statistically significant difference was observed in the incidence of the two types of lung cancer for the three sub-periods (P < 0.05 for squamous cell carcinoma and P< 0.005 for adenocarcinoma). _ 2 _ t I I 1 I I I I I I I I I I

I I I I I I I I I I I I I I Discussion The rates of squamous cell carcinoma and adenocarcinoma in a total of 10481ung carcinoma cases are similar to those described previously (1). The incidence of squamous cell carcinoma declined while the incidence of adenocarcinoma increased significantly, confirming the hypothesis previously proposed. Epidemiological data showed that during the last two decades the incidence of lung cancer continues to increase; thus, as a consequence the mortality due to lung cancer also increased. Specifically, the incidence of lung adenocarcinoma has been rising significantly. More emphasis should be given to the epidemiology and etiology of lung cancer. From a pathological standpoint, more investigations on the relationship between histological types and environmental factors such as smoking as well as airborne pollution and sex are needed. From the point of view of the genesis of lung cancer, squamous cell carcinoma arises from the bronchial epithelium which has already undergone squamous metaplasia ie., repeated proliferation and destruction of cells accompanying chronic inflammation has already occurred. As such, pathological development of squamous cell carcinoma is considered to be a lengthy process. Adenocarcinoma develops in a much shorter time than squamous cell carcinoma since it can arise directly not only from the epithelium of the bronchial tree but from the glands along the bronchial wall as well. Thus, adenocarcinoma tends to occur in younger individuals. More sub-type classification of lung cancer could be beneficial for better understanding the multifactorial nature of lung cancer. - 3 - L

I Reference 1. Li Lie. "Histological Classification and Aetiology Discussion of Lung Cancer in Guangzhou City." Published in the First International Academic Discussion of Pathology. Zhu Hai, China. June, 1988. - 4 - I I I I 1 I I I I I I I I I