Consultation: A Difficult Adnexal Tumor With Divergent Differentiation
A 45-year-old woman has a 2.2 cm deep dermal nodule on the cheek. The outside pathologist diagnosed "benign adnexal tumor" but noted mitoses and a pushing border. Review shows basaloid cells with ductal structures, focal keratinization, and perineural invasion. Immunohistochemistry: CK5/6 positive, EMA positive in ducts, p63 positive in peripheral cells, and Ki-67 ~20%. The case is sent to you for consultation. The clinician asks whether this is benign and whether re-excision is needed.
1. How do the morphology and immunohistochemistry guide the diagnosis?
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Ductal structures with EMA, peripheral p63, and CK5/6 positivity indicate adnexal differentiation, but perineural invasion, mitoses, and a high Ki-67 argue against a benign adnexal tumor. The combination suggests an adnexal carcinoma (e.g., adenoid cystic-like or a basaloid carcinoma with ductal differentiation). Perineural invasion is a key adverse feature requiring margin control. The immunohistochemical profile supports epithelial/adnexal lineage but does not by itself establish benignity; the architectural and perineural findings drive the diagnosis.
2. What is the appropriate recommendation regarding margins and further workup?
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Recommend re-excision with margin control (Mohs or controlled excision) because perineural invasion and a pushing deep border create risk of subclinical extension. The report should state the diagnosis, perineural invasion, and margin status. Further workup could include imaging if there is clinical concern for nerve involvement. The outside diagnosis of benign tumor should be amended or clarified in the consultation report so the clinician understands the change.
3. How should the consultation report be structured to be useful to the clinician and defensible?
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The report should summarize the outside material, state the reviewed findings, give a clear diagnosis with the reasoning, explicitly address perineural invasion and mitotic activity, and recommend margin-controlled excision. It should note any disagreement with the outside diagnosis and the basis for it. Including the Ki-67 and immunohistochemical results with their interpretation makes the report defensible and useful for management.