DS02: External referrals for Mohs micrographic surgery: reject, endorse or enforce ‘in-house review’ of histology slides?
A. Alani and T. Oliphant
Dermatologic Surgery Unit, Newcastle upon Tyne, UK
In other surgical specialties, the practice of reviewing external pathology slides prior to surgery has become routine; however, this is not universal among Mohs surgeons in the UK. This study was prompted by a case referred to our unit in February 2019, as an incompletely excised basal cell carcinoma (BCC) and listed for Mohs micrographic surgery (MMS) in April 2019. Mohs excision was performed in November 2019, when the histology was noted to be in keeping with an infiltrative squamous cell carcinoma (SCC) exhibiting vascular invasion. This change in diagnosis affected patient care and outcome. We conducted a retrospective review of all external cases referred for MMS between November 2019 and December 2020, to evaluate the frequency of in-house review and change in diagnosis. A total of 1027 Mohs cases were performed over a 12-month period; 73 of these cases had been referred by an external provider. Fifteen of 73 of cases were excluded, as the diagnosis was clinical. The majority of cases were BCC (n = 53/58); the remaining cases were SCC and one was Merkel cell carcinoma. In-house review of histology slides was conducted in 21 (36%) cases. The diagnosis was changed from BCC to SCC in two of 21 (9·5%) cases, which resulted in a change in management (surgery was undertaken on an urgent rather than routine basis). Second review of a patient’s outside pathology by a dermatopathologist demonstrates the value of multidisciplinary cancer care in a high-volume cancer centre. Although diagnostic discrepancies were not common, in two of our cases patient management was altered. This has prompted a change in practice at our centre such that all cases with external histology are now reviewed by our dermatopathologists. In-house review of histology slides improves patient clinical outcomes as it mitigates against incorrect diagnoses and inappropriate management.
