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Analysis of 15 years of skin cancer in central Iran (Yazd)

  • Author(s): Noorbala, Mohammad Taghi
  • Kafaie, P
  • et al.
Main Content

Analysis of 15 years of skin cancer in central Iran (Yazd)
Mohammad Taghi Noorbala MD, P Kafaie MD
Dermatology Online Journal 13 (4): 1

Dermatology Department, Shahid Sadoughi Medical Science University of Yazd, Iran. mtnoorbala@gmail.com

Abstract

Skin cancer incidences over a 15-year period (1987-2001) were studied in Yazd, a hot, dry, desert area in the center of Iran. The mean skin cancer frequency was determined to be 28.6 percent and 1,124 patients were diagnosed with skin cancer during this time period, approximately 11 per 100,000. The most common skin cancer was basal cell carcinoma, accounting for 76.9 percent. Squamous cell carcinoma was diagnosed in 18.1 percent and melanoma in 2.7 percent; 2.3 percent were other uncommon skin cancers. Most cancers were diagnosed in the seventh and eighth decades of life. The face, head, and neck were the sites of 92 percent of skin cancers. The sex ratio was determined to be 1.6 (male/female), similar to other reported populations. However, melanoma was found to be 1.5 times higher in men in this study, in contrast to most studied populations. Skin cancer incidence in Iran is lower than western countries. It is very likely that clothing and body covering customs can account for such differences.



Introduction

Skin cancer is one of the most common cancer types in most countries. Skin cancers are usually visible if full skin examinations are performed. If sufficient basic information is given to patients and if physicians and medical students are trained comprehensively, most skin cancers can be diagnosed and treated with minimal costs and facilities [1, 2, 3, 4].

Skin cancer is most often attributed to solar ultraviolet exposure. In tropical countries, those who work outdoors during daytime and those with light skin are more likely to develop skin malignancies [5]. The frequency of skin cancer cases increases with age [6].

In Iran, because of the bright sunlight during most seasons and the direct exposure to the sun of farmers, animal herders, sailors, and construction workers, along with the uncommon use of suitable protective apparel and hats, higher incidences of skin cancer can be expected. Studies of skin cancers within the country have shown a variety of results [7, 8, 9].


Methods

This is a cross-sectional descriptive study using simple census sampling. The sample population consists of patients who have been referred to Yazd Province's health centers between 1987 and 2001 and diagnosed with cancer by the pathology departments. We used data from the cancer registry center of the province for performing this study. Yazd is a province with a population of one million that is located in a relatively warm and dry desert area in the center of the Islamic Republic of Iran.

During the study period, skin cancer reports were collected along with general information including age, sex, occupation, residence, cancer location and type (pathology). Non-skin cancers were recorded as to their types and, for ease of presentation, only the six most common cancer types are reported.

We have divided common skin cancers into the three main categories of basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and malignant melanoma; the other reported non-common skin cancers, which were of six types, were recorded as miscellaneous.


Findings

A total of 3,930 patients with cancer between 1987 and 2001 was reported. Skin cancer with a mean frequency of 28.6 percent over the 15-year study period, was the most commonly reported cancer; 1,124 were diagnosed (Fig. 1). Of these skin cancers, 76.9 percent were BCC, 18.1 percent were SCC, 2.7 percent were malignant melanoma, and 2.3 percent were other less common skin cancers (Fig. 2).

Table 1 shows the frequency distribution of skin cancers according to gender, and as has been demonstrated, skin cancer among men is reported 1.6 times higher than women (61.7 % men and 38.3 % women). Many of the skin cancers in women were noted in the seventh and eighth decades of life.

Table 2 shows the frequency distribution according to age, with 6 age groups studied. The highest frequency of BCC was within the 60-69 year-old group (23.6 %) and SCC within the 70-79 year-old group (22 %). Malignant melanoma occurred most frequently in the 60-69 year-age group (26.7 %).

Table 3 shows the frequency distribution according to occupation. In most instances the highest rate of skin cancer was noted in farmers (22 %).

Table 4 shows the frequency distribution according to the location of the cancer on the body. The facial area alone comprises 71.7 percent of all cases. Overall, 92 percent of all skin cancers occurred in the face, head and neck regions.


Discussion

Epidemiological studies of skin cancers have been carried out across the globe, and the majority of them have reported that skin cancers represent about 20-40 percent of all cancer types [1, 2, 3, 4]. In the United States it is estimated that there are more than one million annual cases of skin cancer [10]. The occurrence rate of skin cancer within the U.S. population is about 300-400 new cases for every 100,000 population per annum [1, 11, 12, 13, 14]. In the United Kingdom, the rate of occurrence is about 100 for every 100,000 per year. The highest numbers relate to Oceania with roughly 800 new cases for every 100,000 people in a year [1, 15]. There are limited studies in Iran, which have estimated the occurrence rate of skin cancers at 10 to 15 new cases per 100,000 population [7, 8, 9]. In the present study, we note approximately 11 new cases of skin cancer per 100,000.

In the United States, Europe, and Australia about 20-25 percent, 20 percent, and 40-45 percent, respectively, of all reported cancers per year are skin cancers [1, 2, 3, 4, 11, 15, 16, 17].

In the present study in Yazd Province, 28.6 percent of all cancers reported are skin cancers. The most common skin cancer is BCC, and in the majority of studies conducted in the United States and Australia, BCC alone comprises around 75 percent and 79 percent, respectively, of all skin cancers [1, 2, 12,14, 15, 17]. A study conducted in Isfahan in 1988 found BCC to make up about 74 percent of skin cancers [7], and a 1991 study in Yazd reported 76 percent [8]. In the present study, nearly 77 percent of skin cancers are BCC.

Skin cancers occur mainly in the sixth, seventh, and later decades of life [1, 2, 14, 15, 17]. In the present study, nearly 70 percent of reported cases of cancer relate to the sixth and later decades. It is important to mention that malignant melanoma has often been observed in lower age groups, the present study also shows a 10 year earlier incidence.

Skin cancers occur mainly in sun-exposed regions, and in the face and neck areas of the body [1, 5, 14, 15]. This study shows that more than 90 percent of reported skin cancers were found in the head and neck regions, which demonstrates the major influence of sunshine on the development of skin cancers.

The frequency of skin cancers in men and women is different. Prior statistics concerning non-melanoma cancers show the incidence in men to be about 1.5 times higher than in women [6, 14, 15, 17]. The present study shows a similar non-melanoma skin cancer ratio with men 1.6 times higher than women. However, melanoma, which is more common among women in other populations, was shown to be 1.5 times higher in men in this study. The 1988 Isfahan study also showed that melanoma was 1.5 times more frequent in men than in women [8]. It is very likely that clothing and body covering customs, and the lower levels of employment of women outside the home in Iran may account for such differences.

Ultimately skin cancer incidence in Iran is lower than western countries, although we still estimate that 7-10 thousand new cases of skin cancer occur in Iran each year. Differences in skin cancer incidence among populations relate to genetic factors, skin type, societal customs (including clothing and body coverings), and cultural issues and habits. It is interesting to see these factors operating in such comparisons between Iran and many other countries, particularly in the sex ratios noted in melanoma. Such comparisons may help us to identify key issues to address in public health education.

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