Basal cell carcinoma histopathologic upgrading and Mohs micrographic surgery: a single institution, retrospective review.

Basal cell carcinoma (BCC) histopathology can differ between original biopsy and wide local excision or Mohs micrographic surgery (MMS). We aimed to analyze the rate of difference in BCC subtypes between the original biopsy and MMS frozen section to determine the rate of histopathological upgrading and also to identify risk factors for upgrading. A single institution, retrospective cohort study of patients with BCC treated with MMS was performed at the University of Texas Southwestern. Screening criteria identified 3235 BCCs. Of these, 1289 tumors were identified as having lower-grade pathology on initial biopsy. 291 (22.6%) of the lower-grade pathology tumors were upgraded to a higher-grade pathology. Tumors with an upgraded pathology had significantly greater number of stages performed [mean of 2.5 vs 2.3, p < 0.001], pre-operative size [median of 1.0 cm vs 0.8 cm, p < 0.001], and post-operative size [median of 2.0 cm vs 1.7 cm, p < 0.001]. These tumors were significantly more likely to require more advanced repairs [36.8% (107/291) vs 29.8% (297/998), p = 0.03] and be referred for post-operative radiation [1.7% (5/291) vs 0.0% (0/998), p < 0.001]. In addition, there were a significantly greater number of tumors considered recurrent (received prior surgical or non-surgical treatment) in the upgraded pathology group [8.6% (25/291) vs 3.9% (39/998), p < 0.01]. Our study highlights that a significant proportion of these patients are under-graded on initial biopsy and would benefit from more definitive intervention, such as MMS.