Purpose
Basal cell carcinoma (BCC) accounts for more than 90% of all eyelid malignancies. Risk factors for BCC include age, ultraviolet light [UV] exposure, genetic background, and fair skin. The objective of this study is to investigate the frequency of periocular BCC subtypes, in particular sclerosing type, in a low UV exposure area (Quebec, Canada) and to compare these results to published data from a high UV exposure area (Australian Mohs Nationwide Database).
Methods
A total of 387 excised periocular BCCs from January 1998 to June 2014 from the Henry C. Witelson Ocular Pathology Laboratory, Montreal, Quebec were evaluated. Demographic data were retrieved, including gender, age, tumor localization, prior clinical diagnosis, histological subtype, and ulceration. For comparisons with a high UV geographic location, we obtained published data (ocular location and histopathological subtype) from the Australian Mohs Database, which includes 1,295 periocular BCC cases.
Results
The average age of our patients was 67.6 ± 15.3 years (range: 8-101). Tumors were more frequent in women (57.1%). Clinical misdiagnosis occurred in 15.2% of the cases, 70% of which were diagnosed as benign lesions. BCC location frequency in descending order was the lower eyelid (58%), upper eyelid (12%), and medial canthus (8.5%). Histopathological subtypes identified were as follows: nodular (79.6%), sclerosing type (7.5%), squamous differentiation (6.5%), sebaceous differentiation (2.8%), and mixed types (3.6%). Twenty tumors were ulcerated (5.2%). The Australian Mohs Database published the following results: 615 (47.5%) BCCs were located in the lower eyelid; 627 (48.3%) in the medial canthus; and 51 (3.9%) in the upper eyelid. The most common subtype in this geographic region was nodular (39.5%) followed by sclerosing type in 34.8% of cases.
Conclusions
There are significant differences in periocular BCC location and subtype between low and high UV geographic locations. In Quebec, the most common ocular location is the lower eyelid, whereas in Australia it is the medial canthus. Sclerosing type was significantly higher in Australia compared to Quebec. The higher UV exposure in Australia relative to Quebec is the likely factor explaining the much higher frequency of this most aggressive type of periocular BCC in the Australian population.