The objective of the DIADERM study was to analyze diagnoses made in the dermatology clinics of members of the Spanish Academy of Dermatology and Venereology (Academia Española de Dermatología y Venerología [AEDV]).1 The study showed that the most common diagnoses made by dermatologists belonged to the following categories of the International Statistical Classification of Diseases, Tenth Edition (ICD-10): L57 (skin abnormalities, such as actinic keratosis), C44 (nonmelanoma skin cancer, such as basal cell carcinoma), and D22 (melanocytic nevi). This finding highlighted the importance of skin cancer in the daily practice of dermatologists.

The caseload generated by dermatologic conditions in primary care is substantial,2 and a considerable percentage of patients are referred from this level to dermatology clinics. Similarly, the dermatologist plays an active role on hospital wards3,4 and in emergency departments.5 Dermatologists show better diagnostic performance with respect to skin tumors (agreement between the presumptive diagnosis of primary care specialists and dermatologists is weaker in skin tumors6). The same is true for therapeutic performance. In addition to being the main parties involved in the surgical treatment of skin cancer,7 dermatologists are more effective and efficient with respect to this condition, according to data from Spain.8 They also achieve a lower percentage of positive margins in keratinocyte carcinoma than other surgical specialties,9 as well as better outcomes in the treatment of patients with melanoma.10

We estimated the prevalence of coded diagnoses in dermatology clinics to measure the demand for outpatient care of tumors by dermatologists in Spain. We also analyzed some of the differences between these diagnoses according to factors such as geographic area, origin of the consultation, and destination of the referral, taking into accout both public and private health care settings.

We performed a cross-sectional observational study based on estimated data on the prevalence of skin diseases collected over 2 periods (January 19 to 21 and May 18 to 20, 2016). The data were obtained via the anonymous DIADERM survey, which was carried out in a random and representative sample of dermatologists in Spain. The methodology and characteristics of the survey (including the data collected and the method for coding the diagnoses) are addressed in detail in the first manuscript of the project.1

The specific analysis of tumors was made by reviewing the complete list of coded diagnoses, from which a total of 165 diseases were selected. Based on the list of selected diagnoses, we formed 24 diagnostic groups, which, in some cases, included more than 1 category from the ICD-10. In order to perform the statistical analyses, the classification was reduced to 4 groups (benign melanocytic, malignant melanocytic, benign nonmelanocytic, and malignant nonmelanocytic) and 2 groups (benign and malignant vs non–tumor-associated disease). In situ keratinocyte cancers (including actinic keratosis, Bowen disease, and leukoplasia) were classified as malignant. Keratoacanthomas were also included as malignant tumors: while these are traditionally categorized as benign, they are now considered a well-differentiated form of squamous cell carcinoma.11 Similarly, cutaneous horns were classified as malignant, since, in a significant percentage of cases, this clinical diagnosis is associated with premalignant or malignant lesions.12

We included variables that had previously been collected in the study, as well as the type of climate (subtropical, Mediterranean, continental-Mediterranean, and oceanic; this variable was created in ecological terms by taking into account the geographic areas of each of the sections and its predominant climate).

The statistical analysis was performed using the survey module of Stata and taking into consideration the design used to collect the sample.13 The module includes standard errors for correlated data. Furthermore, given the real number of dermatologists for each section of the AEDV, which was close to unity, it was not necessary to apply a correction for finite populations.

The study was classified as a non–postauthorization study by the Spanish Agency of Medicines and Medical Devices and approved by the Clinical Research Ethics Committee of the Province of Granada, Spain (October 8, 2014).

Tumors accounted for 46.2% of the diagnoses; 18.5% of all diseases seen at the clinic were malignant. Table 1 shows the population-based diagnoses by group in order of frequency. Of the 10 most common diagnostic groups, in situ keratinocyte tumors were second in frequency, basal cell carcinoma fourth, malignant melanocytic tumors eighth, and squamous cell carcinoma ninth.

Table 2 shows the differences between the variables, taking into account the 4 tumor groups. Malignant tumors were more likely to be the main presenting complaint and the reason for follow-up visits. They were also more likely to be managed in the public health system and less likely to be the definitive diagnosis. The differences were statistically significant.

As for the ecological analysis of the type of climate according to geographic area, we recorded a larger percentage of benign melanocytic tumors in areas with a mainly continental-Mediterranean climate, malignant melanocytic tumors in areas with a mainly oceanic and subtropical climate, and benign nonmelanocytic tumors in areas with a mainly subtropical and Mediterranean climate.

Table 3 shows the results of an analysis of specific variables by comparing non–tumor-associated disease with benign and malignant tumors. Statistically significant differences were observed between the groups with respect to the origin and destination of the referrals. In private clinics, consultations for malignant tumors were proportionally more likely to come from another dermatologist. As for destination, patients with benign tumors were more frequently discharged, whereas those with malignant tumors were usually referred for additional dermatologic care. In the public health setting, malignant tumors were also more likely to be referred from another dermatologist. In more than half of cases, benign tumors came from primary care physicians. Patients with benign tumors were somewhat more likely to be discharged (and less likely to receive additional dermatologic care) in the public setting than in the private setting. As in the private setting, patients with malignant tumors were normally referred for additional dermatologic care. Follow-up was more likely to be with the primary care physician for all diseases, including malignant tumors, in the public setting than in the private setting.

In the present study, we observed that tumors accounted for almost half of the diagnoses made in dermatology outpatient clinics (46.2%) in Spain. Overall, 18.5% of the caseload of specialists in medical-surgical dermatology and venereology in Spain corresponds to malignant tumors (including in situ keratinocyte tumors). If we exclude in situ keratinocyte cancers, this percentage falls to 10.1%. Patients with malignant tumors as the main reason for seeking care tend to be seen more frequently in the public health setting and generate more follow-up visits. Differences were also observed with respect to the origin and destination of the consultations, depending on whether they were managed in the private or public setting, although this could be affected a priori by organizational factors.

The method followed to classify patients was similar to that used in other studies in Europe, insofar as tumors were classed as benign and malignant.14,15 This approach attempted to be more inclusive than in other studies, where the only cancers taken into consideration were basal cell carcinoma,16 squamous cell and basal cell carcinoma,17 and nonmelanoma skin cancer.13 Given that keratoacanthoma was traditionally considered benign and cutaneous horns as benign or malignant, we also performed a sensitivity analysis including both diagnoses as benign tumors and found no significant variations in our findings (data not shown).

Although differences in diagnoses were analyzed according to geographic region, this was not specifically by comparing rural and urban areas, as in a study performed in Australia.18 In any case, we believe that the manner in which the data were analyzed provides a more complete idea of the real caseload of skin tumor diagnoses in Spain than other approaches, since not all tumors require surgery8 or are managed via interdepartmental consultations (with the percentage of activity above the 5.7% that interdepartmental consultations for skin cancers were thought to represent19).

Dermatologists’ caseload has grown in recent decades, with a clear increase in tumor diagnoses.6,13–15 The economic impact of skin cancer on health systems is growing and clear, and according to a recent study based on data from public hospitals in Portugal, it is 4-fold greater when the overall number of nonmelanoma cases is compared with the number of melanoma cases.20 Some groups have proposed new forms of multidisciplinary and integrated management of patients with skin tumors.21 The specialist in medical-surgical dermatology and venereology clearly plays a key role in the care of these patients.

Our study has a series of strengths, such as the methodology used (representative of the demand for dermatologic care) and its sample size, which enabled us to report accurate results. Its limitations include potential error in measuring the ecological variable climate (which was generated based on the predominant one and only for purposes of generating a hypothesis).

Almost one-fifth of the caseload of specialists in medical-surgical dermatology and venereology in Spain corresponds to malignant cutaneous tumors. Differences are observed between diagnoses based on factors such as the care setting (public vs. private), the geographic area, and the origin of the consultation and destination at discharge. Additional studies are warranted to analyze these factors and determine whether they are due to geographic, cultural, or organizational aspects or to variability in clinical practice.

The DIADERM study was promoted by the Healthy Skin Foundation of the Spanish Academy of Dermatology and Venereology (Fundación Piel Sana de la Academia Española de Dermatología y Venereología), which received funding from Novartis. The pharmaceutical company did not participate in data collection, data analysis, or interpretation of the results.

The authors declare that they have no conflicts of interest.