Predicting the Surgical Margin of Resection in Periocular Cutaneous Neoplasms and the Significance of Reconstruction Following Mohs Micrographic Surgery

Purpose: To evaluate the features of periocular cutaneous malignancies that may contribute to larger surgical defects or require more complex reconstructive procedures. Methods: A retrospective review of 181 patients with biopsy proven periocular cutaneous malignancies seen between April 2005 and September 2010, and undergoing Mohs micrographic surgery was performed. The longest horizontal and vertical diameters of the tumor and the post-Mohs surgical defect were measured in each patient. These measurements were used to calculate the relative margin of resection (MOR) required for tumor eradication as well as the size of the surgical defect. The date of surgery, histologic diagnosis and location of the tumor, type of reconstruction, and the presence of recurrence were also recorded. Results: The average MOR for all tumor subtypes taken together was 3.4 mm horizontally and 2.6 mm vertically for basal cell carcinomas (BCCA). The post-Mohs defect area was 3.2 times greater than the preoperative tumor area for all BCCA subtypes, and 3.9 times greater for morphea type (p = 0.8083). The average MOR for squamous cell carcinomas (SCCA) was 5.1 mm horizontally and 3.7 mm vertically. The post-Mohs defect area was 3.8 times greater than the preoperative tumor area for SCCAs. When comparing the preoperative horizontal tumor diameter to the horizontal MOR of BCCAs and SCCAs, the correlation was 0.23 (p < 0.0001) and 0.31 (p < 0.0001), respectively. While the average MOR was within standard limits, a significant number of tumors required a greater MOR. On review of the data, 30.6% of patients with BCCA required a MOR greater than 3 mm, 17.3% of patients with BCCA required a MOR greater than 4 mm, and 29.1% of patients with SCCA required a MOR of greater than 5 mm. Tumors located at the lateral canthus required the largest MOR (p < 0.01), while those on the lower eyelid were associated with the smallest MOR in BCCAs. As expected from anatomical considerations, tumors at the medial canthus required significantly more complex reconstruction procedures (p < 0.01). An ordered logistic regression model demonstrated that BCCA preoperative clinical tumor surface area was a significant indicator for the degree of reconstruction required (p < 0.01). Conclusions: Standard 3 mm to 4 mm MOR for BCCAs, and 5 mm MOR for SCCAs could result in an unacceptable risk of tumor recurrence if the surgical margins are not examined histologically. With increasing preoperative tumor size, there is an increase in the MOR required for BCCA and SCCA, supporting that large tumors require a greater MOR.