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On-line version ISSN 1806-4841
An. Bras. Dermatol. vol.80 no.4 Rio de Janeiro July/Aug. 2005
CLINICAL, EPIDEMIOLOGICAL, LABORATORY AND THERAPEUTIC INVESTIGATION
Epidemiology of basal cell carcinomas in Blumenau, SC, Brazil, from 1980 to 1999*
Doutor em Dermatologia pela Universidade Federal do Rio de Janeiro - UFRJ - Rio de Janeiro (RJ), Brasil; Especialista em Dermatologia pela SBD e Professor Titular da Disciplina de Dermatologia do Curso de Medicina da Universidade Regional de Blumenau - FURB - Santa Catarina (SC), Brasil
Morbidity from basal cell carcinomas is increasing worldwide. In Brazil there
are no studies about morbidity rates of this type of cancer.
OBJECTIVES: To determine morbidity and to analyze and classify the basal cell carcinomas diagnosed in the city of Blumenau, from 1980 to 1999, according to their major clinical and histological features.
METHODS:The author reviewed the histopathological findings of two laboratories of the city of Blumenau, considering the variables sex, age, primary site and histological type. The morbidity rates were calculated using the number of basal cell carcinomas found and the annual population estimated from 1980 to 1999.
RESULTS: A total of 5254 tumors were identified, with a higher incidence in females and in subjects older than 50 years. Primary site in exposed areas was predominant. Morbidity rates varied from 51.5 cases per 100,000 inhabitants/year in 1980 to 225 cases per 100000 inhabitants in 1999.
CONCLUSIONS: Basal cell carcinomas in Blumenau have distribution patterns similar to those reported in the literature regarding age, anatomical site and histological types. Morbidity rates of this tumor were found in the Brazilian literature.
Keywords: Carcinoma, basal cell/epidemiology; Morbidity; Neoplasms
Basal cell carcinomas are the most common type of skin cancer and account for approximately 70-75% of cases in all statistical studies.1-5 This study found that 65.7% of all cases diagnosed with skin cancer in the city of Blumenau were basal cell carcinomas.
Morbidity data involving basal cell carcinomas separately are virtually inexistent in the literature for these types of cancer are usually considered together with squamous cell carcinomas and classified as non-melanoma skin cancer.6
In the U.S., Scotto1 ound 233 non-melanoma skin cancers/100000 inhabitants/year. The highest records were found in Northern Australia with 1000 to 2000 cases/100000 inhabitants/year.7-9
In 1994, in the U.S., approximately 900000 to 1200000 North Americans were expected to present non-melanoma skin cancers.10
In this study we aimed to demonstrate the morbidity rates of basal cell carcinoma in the city of Blumenau, from 1980 through 1999, and its main clinical and histological characteristics, considering sex, age, primary site and histological types.
The results represent data which are new for Brazil and may be used as a reference for practically the whole southern region of the country, where the population is predominantly Caucasian and exposed to very intense ultraviolet radiation.
MATERIAL AND METHODS
The morbidity rates of basal cell carcinomas for the city of Blumenau were calculated based on the annual population from 1980 through 1999, estimated by the Instituto Brasileiro de Geografia e Estatística (IBGE) [Brazilian Institute of Geography and Statistics],11 and on a survey of cases histopathologically diagnosed by two local laboratories - Cipac (Laboratório de Citologia, Imunopatologia e Anatomia Patológica) and BML Patologia (Laboratório Beatriz Moreira Leite), from 1980 to 1999. The number of basal cell carcinomas diagnosed within that period was 5254. When the cases were reviewed, only those originating from the city of Blumenau were considered, in order to enhance reliability of morbidity rate calculation. Statistical analysis was performed using association tests and the chi-square test.
A total of 5,254 cases of basal cell carcinomas were diagnosed in the pathology laboratories of the city of Blumenau, SC, corresponding to 65.7% of all skin cancers diagnosed (Table 1).
The distribution of cases by sex was 2571 males (48.9%) and 2683 females (51.1%), as shown in table 1.
Table 2 depicts the percentage distribution of basal cell carcinomas according to age groups and sex, showing that the age group with the highest incidence of this type of carcinoma is 50-69 years.
The percentage of basal cell carcinomas according to their primary site is found in table 5. It can be noted that 46.7% of the cases were found on the face, the total amounting to 81.2% on the head and 18.8% on trunk and limbs.
Table 6 shows the percentage of histological types of basal cell carcinomas found in the study, classified according to Mackie,12 The superficial spreading type was the most frequent and accounted for 45.3% of cases, and the sclerosing type, which is more invasive and destructive, accounted for 10% of cases.
There were 5254 cases of basal cell cancer diagnosed. This is, however, an absolute number that cannot be compared with other absolute numbers found in Brazilian and foreign studies. Therefore, the morbidity rates per 100000 inhabitants/year were calculated, enabling comparisons with other rates reported in the literature, mainly those related to Australia and the United States.13
The morbidity rates help evaluating the increased or decreased incidence of skin cancer; and, in this case, the behavior of basal cell carcinomas in Blumenau over 20 years.
There was a considerable increase in morbidity, from 51.5 cases/100000 inhabitants, in 1980, to 225 cases/100000 inhabitants, in 1999 (Graph 1).
This roughly 430% increase could be explained by the number of diagnoses made in the city, intense solar radiation and the habit of sun exposure.
The highest incidence was among women, representing 51.1% of cases, although the difference cannot be considered significant (p>0.05); in the literature the incidence in both sexes is virtually the same.13-15
As to age, the highest incidence was in the 40-60 year group, which agrees with other studies.1,13-15 The primary site of most of the basal cell carcinomas (77.75%) was in exposed areas, like in other statistical surveys.2,6,15,16
The incidence of basal cell carcinomas on the ear pinna was higher in men (63.64%) than in women (36.4%), probably due to an important epidemiological factor: the hair length covering the female pinna, with the consequent natural protection against ultraviolet radiation. This difference can be considered statistically significant (p<0.05).
Furthermore, a higher incidence was found on the nasal pyramid of women (62.6%) compared to men (37.4%), which is statistically significant (p<0.05). The incidence of basal cell carcinomas in lower limbs was higher in females (58.3%) than males (41.67%) and wearing trousers could be considered an important protection factor for male lower limbs.
As to histology of basal cell carcinomas, the type most frequently found was the superficial spreading, but it is worth mentioning that 10% of cases were of the sclerosing type, which is considered the most aggressive and difficult to treat.16
The population studied resides in the city of Blumenau, SC. The majority is Caucasian, of German and Italian (from northern Italy) descent; thus, the skin types most often found were I and II, according to the Fitzpatrick classification.11-17
The white race has less melanin pigments than the mulattoes and blacks, therefore being more subject to solar radiation effects.3-18
The risk of developing basal cell carcinoma is higher in whites, who have difficulties in becoming tanned, tend to get sunburns, and have fair hair and blue eyes.2,14,19,20
Epidemiologic evidence indicates that there is a relationship between excessive sun exposure and the risk of developing skin cancer, especially non-melanoma carcinomas. Ultraviolet radiation is the most important risk factor.19-21
The ultraviolet radiation that reaches the population of Blumenau during the summer (Chart 1), measured by the Instituto Nacional de Pesquisas Espaciais (Inpe) [National Institute of Space Research], shows a UVB-Index of 11.5, which is higher than in Brazilian cities nearer to the Equator (Chart 2) and considered very high according to chart 3.
The higher the UVB radiation, the greater the incidence of skin cancer, and this kind of radiation also depends on the ozone layer that filtrates ultraviolet radiation (Chart 2)21-23
The ozone layer in the region of Blumenau can be considered reduced as compared to other Brazilian localities with latitudes closer to the Equator, while it actually should be more concentrated (Chart 3) since the ozone layer decreases from the poles toward this line22,23
In a sample of 5254 basal cell carcinomas diagnosed over a 20-year period and with annually determined morbidity rates, it was found that there was a progressive increase in these rates from 1980 to 1990 (430%), with a slight predominance in women (51%).
The highest incidence was found in the population aged over 40 (88.9%), with a significant presence under this age.
The primary site was predominant in exposed areas, and the most common histological type found was superficial spreading basal cell carcinoma (45.3%).
The increased ultraviolet radiation due to reduced ozone layer concentration over the Blumenau region could be included among the main factors contributing to the increase in basal cell carcinomas.
Based on the data found in this study, it can be concluded that the white population of Blumenau with phototypes I and II and exposed to intense sun radiation is at great risk of developing basal cell carcinoma.
Basal cell carcinomas constitute a major public health problem in this city, requiring health education programs for all age groups as of childhood, aimed at prevention, photoprotection and adequate conditions for early diagnosis and treatment of the disease, thus preventing greater damage that could be caused by this kind of skin cancer.
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20. Karagas MR, Stukel TA, Greenberg ER, Baron JA, Mott LA, Stern RS. Risk of subsequent basal cell cancer and squamous cell cancer of the skin among patients with prior skin cancer. JAMA. 1992; 267:3305-10. [ Links ]
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22. World Health Orgnization Geneva: 1994. International Programme on Chemical Safety. Environmental health criteria 160 ultraviolet radiation. [ Links ][cited 2004 nov] Available from: http://www.inchem.org/documents/ehc/ehc/ehc160.htm.
23. Department of the Environment Protection: 2004. Stratospheric ozone depletion and its possible impacts in the UK [ Links ]
Correspondence Received on January
05, 2004. *
Work done at Universidade Regional de Blumenau - FURB - Santa Catarina (SC),
Rua Curt Hering, 20 - 3° Andar - Centro
89010-030 - Blumenau - SC
Tel./fax: (47) 322-3143
Approved by the Consultive Council and accepted for publication on June 27, 2005.
Received on January
* Work done at Universidade Regional de Blumenau - FURB - Santa Catarina (SC), Brazil.