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Pigmented Plaque in the Axilla

Educational Objective
Based on this clinical scenario and the accompanying image, understand how to arrive at a correct diagnosis.
1 Credit CME

A woman in her 70s presented with an enlarged and variegated plaque on her left axilla, which she had had for 4 years. The lesion started as a small eczematous, pink-to-brown plaque. As the lesion was asymptomatic and slow growing, she did not initially seek treatment. Recently, the color of the lesion had changed to an alarming dark brown color (Figure, A). No breast mass or lymphadenopathy was observed. Her medical and family history was unremarkable. A skin biopsy specimen was obtained and submitted for further histopathologic analysis.

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C. Pigmented extramammary Paget disease

An incisional biopsy revealed an intraepidermal neoplasm consisting of pagetoid cells, characterized by a round, pale vacuolated cytoplasm and large pleomorphic nuclei. Immunohistochemical staining revealed that the lesion was positive for CK7, EMA, and surrounded by numerous reactive dendritic HMB-45–positive melanocytes scattered among the tumor cells (Figure, B-D). Based on these clinical and histologic manifestations, a diagnosis of pigmented extramammary Paget disease (EMPD) was formulated.

Extramammary Paget disease is an intraepithelial adenocarcinoma that most commonly involves the vulva but can also occur in the perianal skin, scrotum, penis, and axilla. It is sometimes associated with underlying adnexal or visceral cancer. Extramammary Paget disease usually manifests as dermatitis and/or eczematous lesions.1 Occasionally, the lesion is pigmented. Pigmented EMPD is a very rare clinical-pathologic variant of EMPD. Although its clinical features are often indistinct and difficult to distinguish from other pigmented entities, appropriate histologic and immunohistochemical analysis is essential in securing a definitive diagnosis.

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Article Information

Corresponding Author: Jiu-Hong Li, PhD, Department of Dermatology, the First Hospital of China Medical University, Shenyang 110001, China (pfkl2011@126.com).

Published Online: September 16, 2020. doi:10.1001/jamadermatol.2020.3250

Conflict of Interest Disclosures: None reported.

Funding/Support: This research is supported by grants from the National Natural Science Foundation of China (81803148) for data collection and patient management.

Role of the Funder/Sponsor: The National Natural Science Foundation of China had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Additional Contributions: We thank the patient for granting permission to publish this information. We also thank Dr Song Zheng, MD, PhD, The First

Hospital of China Medical University, for his assistance in pathology. He was not compensated.

References
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