The Accuracy of Measurements of Nonmelanoma Skin Cancer Sizes Referred to the Mohs Surgery Clinic

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Tumour size is a crucial factor used to plan Mohs procedures. Larger tumours require more time and stages of excision, and they need to be triaged as a higher priority. Therefore, the accuracy in measurement of tumour size is critical.


To investigate if there is a significant difference in accuracy of tumour measurements in referrals between dermatologists and nondermatologists.

Methods and Materials:

Performed a retrospective study of 180 referrals from dermatologists and 47 referrals from nondermatologists to The Ottawa Hospital Riverside Mohs Surgery Clinic. We compared the mean size difference of tumours between the preoperative size and the size reported on referral.


Average reported size upon referral of nonmelanoma skin cancer (NMSC) was 1.39 cm2 and 1.35 cm2 from dermatologists and nondermatologists, respectively (P = .881). During the preoperative assessment, tumour sizes were 0.65 cm2 and 1.45 cm2 larger than that reported from dermatologists and nondermatologists, respectively (P < .05). The duration between referral and preoperative assessment was 3 to 4 months for both groups (P = .26).


The accuracy of tumour measurements between dermatologists and nondermatologists differed significantly, as nondermatologists underestimated the size of NMSCs. This directly affects triaging patients and operative management in Mohs surgery. To compensate for size underestimation, early and prompt referrals of NMSCs from nondermatologists are warranted.

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