A Rare Case of Axillary Extramammary Paget's Disease with an Underlying Adenocarcinoma.

Extramammary Paget's disease (EMPD) is an uncommon cutaneous neoplasm almost exclusively located in the vulvar, perianal, and male genitalia regions. Evaluation and management are complicated given the average delay in diagnosis is two years and approximately 30% of cases are associated with underlying malignancies. The axilla is a unique location for EMPD. We report a rare case of a 78-year-old male with axillary EMPD associated with an underlying adenocarcinoma. A 1-cm tender and pruritic erythematous plaque with surrounding erythema appeared in the patient's axilla. An irritated seborrheic keratosis secondarily impetiginized along with irritant contact dermatitis was suspected. Treatment of cefdinir and topical hydrocortisone failed and a biopsy was taken. Microscopic and immunohistochemical examination showed ulceration with an underlying proliferation of atypical glands (Figure 2A) and a nested intraepidermal proliferation with pagetoid spread (Figure 2B). The atypical cells were positive for gross cystic disease fluid protein 15 (Figure 2C), epithelial membrane antigen (Figure 2D), cytokeratin 5/6, and cytokeratin 7. These findings were supportive of an apocrine adenocarcinoma arising in association with EMPD. Wide location excision was performed. Screening for associated malignancies or lymphatic spread is the primary goal during evaluation. Outcomes are favorable when the primary neoplasm is of limited distribution. The accepted treatment for primary lesions is wide local excision, although anatomic tissue constraints necessitate further research into other treatment modalities. To our knowledge, this is the 14th reported case of axillary EMPD with an underlying adenocarcinoma which may help with identification and management of future cases.