The study's descriptive statistics for the overall population, regardless of follow-up, are consistent with those of other authors. However, it is important to consider differences in study design, population composition, and epidemiological factors based on the geographic distribution of study populations, which may result in varying impacts of risk factors. Other studies have also detected a preponderance of affected female patients [2, 9] and a mean age of 71 ± 12 years [2, 4, 10].
When comparing this study to other authors [11–14], divergent data resulted from differences in classification and nomenclature of the various tumor subtypes. While the percentage of different subtypes of the overall cases of basal cell carcinoma that have been regarded can vary, all the results of other authors taken into consideration confirmed that the nodular subtype is the most frequent both in studies that included several body sites [12, 14] as well as in studies that focused on periocular basal cell carcinomas [13, 15, 16]. The study analyzed most basal cell carcinomas and found that they affected the left eye. This supports Wong et al.'s hypothesis using right-hand or left-hand-drive vehicles may influence the localization of a developing basal cell carcinoma [15]. Several authors have confirmed the order of periocular tumor presentation as follows: lower lid, medial canthus, upper lid, and lateral canthus [2, 4, 17–19]. Although ulceration is generally considered less critical, Lara et al. analyzed basal cell carcinomas in a population that primarily presented non-ulcerated tumors [20]. Zimmermann and Klauß exclusively considered eyelid and periorbital basal cell carcinomas, describing 60% of cases without ulceration [19]. Resti et al. reported a higher percentage of recurrences, amounting to 19.1% of all analyzed cases, while Knani et al. found that only 4.7% were recurrences [18, 21]. In this study, 9.31% of all basal cell carcinomas considered were described as recurrences of previous cases. In Resti et al.'s study, 27.3% of basal cell carcinomas had a horizontal diameter of more than 10mm, indicating a higher proportion of larger tumors than ours, where only 10% of cases measured more than 10mm [21]. The study found that the percentage of incompletely excised basal cell carcinomas, regardless of follow-up, was relatively low at 1.8% compared to other studies. Spraul et al. described 52.4% of cases as incompletely excised. However, re-excisions were not administered in contrast to our study. [22] Zimmermann and Klauß found a total of 198 cases of basal cell carcinoma in the periorbital region, of which 35% presented positive margins after the first excision and were either re-excised or clinically followed [19].
If only cases with a follow-up of more than a year are considered, the recurrence rate in this study amounts to 16.95%. When comparing this rate to the results of other studies, it is essential to note the differences in operation methods and study design. Resti et al. describe a lower recurrence rate of 1.8%, but basal cell carcinomas were treated with frozen section controlled excision, a procedure generally associated with lower recurrence rates [21, 23]. Spraul et al. achieved a recurrence rate of 2.3% of the regarded cases that were excised entirely [22]. While the overall number of 95 analyzed cases, as well as the mean follow-up of 2.6 years, is similar to our study, it is essential to consider that the minimum follow-up of three months compared to the minimum follow-up of a year in our study could affect the recurrence rates [22]. In a systematic review by Kakassery et al., the overall recurrence rate of completely excised eyelid basal cell carcinomas is estimated at 30%, most occurring within the first five years after excision [6].
The statistical results of Zimmermann and Klauß support our results insofar that the patient’s sex, age at first diagnosis, periorbital localization and ulceration of the tumor do not show significant correlations to the recurrence rate of basal cell carcinomas [19]. However, in contrast to our study, both the sclerosing subtype and the complete excision of the tumor showed significant results [19]. The S2K-Guidelines of Cutaneous Basal Cell Carcinomas also define sclerosing or infiltrative subtypes, as well as a horizontal diameter of more than 6mm in the periorbital region and previously recurred basal cell carcinomas as risk factors that are associated with higher recurrence rates [10]. Several possible reasons why these parameters were not significantly correlated to the recurrence rate of basal cell carcinomas in our study.
Regarding the histologic subtype and its correlation to the recurrence rate, it is vital to consider that in our study, an initial case number of nine sclerosing basal cell carcinomas had to be narrowed down to four cases due to follow-up periods that didn’t exceed one year. The question of whether mixed subtypes should be regarded as a separate group or classified as subtypes of one or the other presented growth pattern could also lead to different case numbers and, therefore, various test results.
Concerning the status of a basal cell carcinoma being a primary lesion or a recurrence, we could determine a higher recurrence rate within the group of recurred tumors. However, no significant correlation was identified in the statistical analysis. It should be noted that within the group of primary basal cell carcinomas, the number of cases of aggressive histologic subtypes as well as incompletely excised tumors was higher than in the group of recurred basal cell carcinomas, possibly affecting the results as well as not confirming the observation of several authors that recurring tumors can develop into more aggressive subtypes [4, 18–21] and therefore complicate complete excision. Nonetheless, Resti et al., as well as Knani et al., also conclude in their respective studies that no significant correlation could be found between a tumor being a primary lesion or a recurred lesion and the recurrence rate. The treatment choice in both these studies differs from ours [18, 21].
The study we conducted found no significant difference in the horizontal diameter of basal cell carcinomas between recurring and non-recurring lesion groups. However, we observed that the recurrence percentage was slightly higher in larger tumors measuring 5.1-10mm compared to those measuring less than 5mm. Some studies suggest that larger tumors have a higher tendency to recur [19–21, 24], but it's essential to differentiate between the horizontal and vertical diameters of basal cell carcinomas. Unfortunately, we couldn't gather much information about the vertical extent of the tumors in our study. Our results are limited to the analysis of horizontal diameters of a reduced number of cases due to follow-up periods that didn't meet the inclusion criteria we defined. Zimmermann and Klauß found no significant correlations in analyzing the recurrence rates of different tumor diameters. They stated that higher recurrence rates weren't seen until diameters measured more than 20mm [19].
Many authors conclude that the correlation between a complete or incomplete excision of basal cell carcinomas and the recurrence rate is significant [19, 22]. The S2k-Guidelines for Cutaneous Basal Cell Carcinoma recommend re-excision after an incomplete removal of the tumor has been histopathologically diagnosed [24]. In our study, the rate of recurrences was higher among the incompletely excised cases; a significant correlation, however, could not be verified. This result can be because our study's overall case number of incompletely excised basal cell carcinomas was low, and nearly all tumors were re-excised until clear resection margins were achieved.
It is important to note that many authors link parameters related to the ability to remove basal cell carcinomas altogether to the recurrence rate of the same. Clear or involved resection margins are considered important predictors of possible recurrences. According to several authors, the difficulty of completely excising aggressive subtypes can be caused by their noncontinuous and subclinical growth, leading to higher rates of incompletely excised lesions [19, 22, 23]. Previously recurred basal cell carcinomas are described as potentially transforming into more aggressive subtypes, as stated in multiple publications [4, 18–22]. The S2k-Guidelines for Basal Cell Carcinomas mention a positive correlation between the horizontal diameter of a lesion and the likelihood of subclinical tumorous residuals [24]. The limited possibility of extensive tissue removal in the eyelid region poses a further challenge to the achievement of clear resection margins.