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It’s a misconception that skin cancers are invariably “prosaic” basal cell carcinoma (BCC), SCC, or malignant melanoma. Skin cancers are fascinatingly varied and complex. Microcystic adnexal carcinoma (MAC) is a good example of an underappreciated skin cancer which can be misdiagnosed, inadequately excised, and highly destructive.
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An 84-year-old woman presented for margin control surgery (MCS) with a tumor of the cheek which had been previously biopsied and diagnosed as a BCC. The slides were reviewed prior to the surgery. The pathologist noted that areas of the biopsy showed a highly infiltrative growth pattern, areas of ductal differentiation, and infiltration of small nerves. These findings were interpreted as more in line with a MAC rather than a BCC (Fig. 17.1).
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MCS was performed. The first excision was a central scalpel debulk which was sent to an outside laboratory in formalin for paraffin processing (Fig. 17.2). This facilitated a comprehensive histopathologic examination and confirmed the diagnosis of MAC. The first level was excised with approximately 2-mm clinical margins around the central debulk defect. The first-level histologic sections showed extensive tumor involving the entire radial margin (Fig. 17.3). The deep margin was negative for malignancy. The case was discussed with a remote dermatopathologist using a telepathology system utilizing an adapter and smartphone with a teleconference application.
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Three further levels were needed to achieve negative margins. At this point, almost the entire cosmetic subunit had been removed, so the remainder of that subunit was then demarcated and removed. This specimen served as a safety margin which was embedded in paraffin for margin assessment (Figs. 17.4 and 17.5). The defect was left open until the safety margin was confirmed to be negative for malignancy. Due to the size of the defect and its location, quite a meticulous reconstruction was needed (Fig. 17.6).
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