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DP22: Invasive mammary‐type carcinoma arising in a patient with extramammary Paget disease of the scrotum

Uncommon presentations of malignant melanoma: a diagnostic challenge N. Marcellin, R. Singh-Raghunath, S. Crippa and B. De Silva Departments of Dermatology and Histopathology, Luton and Dunstable University Hospital, Bedfordshire Hospitals NHS Foundation Trust, Luton, UK The diagnosis of some subtypes of malignant melanoma can be challenging due to their unusual presentations and resemblance to benign skin lesions (Cabrera R, Recule F. Unusual clinical presentations of malignant melanoma: a review of clinical and histologic features with special emphasis on dermatoscopic findings. Am J Clin Dermatol 2018; 19 (Suppl. 1): 15–23). We report five cases that illustrate the clinical and histopathological pitfalls. Case 1 was a 54-year-old woman who had a 7-mm pink/purple papule over her abdomen for 20 years with recent scabbing. Excision biopsy confirmed stage 1b superficial spreading melanoma with a Breslow thickness (BT) of 1 1 mm. She was offered wide local excision (WLE) and sentinel lymph node biopsy (SLNB). Case 2 was a 65-year-old woman who presented with a nonhealing ulcerated lesion on her left heel of 1 year’s duration. Examination showed a 2 cm erythematous eroded area with a polypoid vascularized edge and nonspecific dermoscopic features. Histopathology revealed a stage 2C acral melanoma with a BT of 7 mm. A WLE was performed with skin graft, but SLNB was declined. Two years later she had a local recurrence presenting as a 3-mm papule on the foot. Staging scans showed lymph node and brain metastasis. Case 3 was a 60-year-old woman who had a discoloured painful left fifth toenail with oozing of 2 years’ duration. Fungal cultures were repeatedly negative. A diagnostic biopsy from the nailbed revealed invasive melanoma with a BT of 1 5 mm requiring amputation. Three years after the primary diagnosis, she had metastatic disease to groin nodes. Case 4 was a 69-year-old woman who presented with an asymptomatic 4 9 7-mm firm pink nodule on her right shoulder of 1 year’s duration without any epidermal changes. Dermoscopy showed no specific features. Excision biopsy showed a dermal tumour associated with massive neurotropism and a BT of 2 4 mm, consistent with a stage 2A neurotropic variant of malignant melanoma. At a recent follow-up, a subcutaneous nodule was noticed on the left back and excision biopsy revealed metastatic neurotropic melanoma. Case 5 was a 70-year-old woman who had ignored a nodule on her left arm for 1 year until it became inflamed and painful. Examination revealed a 4-cm subcutaneous nodule without any specific dermoscopic features. Excision biopsy showed a dermal tumour nodule of melanoma with no connection to the overlying epithelium suggestive of a primary dermal melanoma. Staging scans showed no other disease. We need to show a high degree of suspicion when diagnosing skin lesions, especially in acral sites. Although dermoscopy is a useful tool in early detection, features can be variable or absent. Histopathology with specific immunohistochemical markers is the cornerstone of diagnosis. DP22 Invasive mammary-type carcinoma arising in a patient with extramammary Paget disease of the scrotum J. Kentley, N. Francis, M. Ratynska and C. Bunker Memorial Sloan Kettering Cancer Center, New York, NY, USA; Imperial College Healthcare NHS Trust, London, UK; and University College London Hospitals NHS Trust, London, UK A 78-year-old man presented with an 18-month history of a lump on the left side of his scrotum. There was a 10-year history of an inguinal rash, previously treated as psoriasis. On examination, he had a 2 9 2 cm exophytic nodule on the left hemiscrotum and extensive inguinoscrotal erythema, maceration and ulceration. Histology showed proliferation of malignant cells with eosinophilic cytoplasm within the epidermis displaying the pattern of extramammary Paget disease (EMPD). An underlying invasive adenocarcinoma was seen in the dermis. The tumour was composed of files and trabeculae of atypical cells resembling mammary lobular carcinoma and ducts populated by highly atypical epithelial cells with comedo necrosis, displaying the appearance of mammary ductal carcinoma in situ (DCIS). Tumour cells were positive for carcinoembryonic antigen, epithelial membrane antigen, CK7, GATA3 and androgen receptor. EMPD occurs predominantly on apocrine gland-bearing skin of the anogenital region. It may be classified as primary or secondary, the latter often representing intraepithelial spread of an underlying urogenital or gastrointestinal carcinoma [Konstantinova AM, Spagnolo DV, Stewart CJR et al. Spectrum of changes in anogenital mammary-like glands in primary extramammary (anogenital) Paget disease and their possible role in the pathogenesis of the disease. Am J Surg Pathol 2017; 41: 1053–8]. Clinically, EMPD presents as slow-growing erythematous patches and plaques that may ulcerate. Diagnosis is frequently delayed as lesions may resemble inflammatory or infective dermatoses. Histopathology reveals Paget cells in the epidermis, sometimes with accompanying acantholysis. Adnexal involvement is common. Immunohistochemical examination is essential (Kazakov DV, Spagnolo DV, Kacerovska D, Michal M. Lesions of anogenital mammary-like glands: an update. Adv Anat Pathol 2011; 18: 1– 28). The histogenesis of primary EMPD is yet to be fully defined. It is hypothesized that the condition originates from apocrine or eccrine adnexal structures, or keratinocyte stem cells. DCIS or invasive mammary carcinoma are rarely associated with primary EMPD, but, when present, supports the theory that EMPD may arise from underlying anogenital mammary-like glands (AGMLG), a normal constituent of the anogenital region in both men and women, with upward migration of malignant cells into the epidermis (Kazakov et al.). One recent study found alterations of AGMLG in 33 of 181 EMPD cases, observing a morphological spectrum of ductal lesions from dysplasia to DCIS (three cases) and invasive mammary-type carcinoma (four cases), analogous to the malignant changes that occur in the breast (Konstantinova et al.). Although likely only representing a subset of cases, clinicians should be aware of EMPD developing from AGMLG