Histological Spectrum Of Lesions That Affect The Anogenital Mammary Glands

DP01 Histological spectrum of lesions that affect the anogenital mammary glands M.K. Lakhan, N. Lalagianni, F. Lewis, C.M. Stefanato and E. Calonje Departments of Dermatology and Dermatopathology, St John’s Institute of Dermatology, London, UK The anogenital mammary-like glands were first described by van der Putte in 1991 and are mainly found in the interlabial sulci. They have distinct features that are similar to breast tissue and can develop similar benign and malignant changes. We present three cases to highlight the spectrum of lesions that can affect the anogenital mammary glands. A 45-year-old woman presented with a left labium majus lump that had been enlarging over the last few months. On examination, she had a large mobile cystic lesion in the left labium majus, with clinical features in keeping with a vulval cyst. In view of the size of the lesion, it was excised. Histology confirmed a diagnosis of a benign fibroadenoma of mammary type. An 83year-old woman presented with an enlarging left vulval lump. Histology confirmed an incomplete excision of a low-grade adenocarcinoma arising from mammary-like glands. Further excision confirmed a primary adenocarcinoma, but inguinal nodes were involved, with metastatic disease. Imaging confirmed no distant spread and she completed a course of adjuvant radiotherapy. A 33-year-old woman with a background of ovarian cancer (borderline mucinous) treated with surgery and omentectomy presented with a 5-year history of a lump in the right groin. Magnetic resonance imaging was inconclusive, as was a fine-needle aspiration. A core biopsy was undertaken, which showed a possible adnexal tumour and she was referred for excision. On examination, a firm 6-cm mass was palpable in the right inguinal fold. There were no lymph nodes palpable. Histology showed features suggestive of an adenocarcinoma of the anogenital glands. These cases represent the spectrum of lesions that originate from the anogenital mammary-like glands. Fibroadenomas are benign tumours that present as well-circumscribed, asymptomatic nodules and have a biphasic histological appearance, epithelial and stromal, with scattered bland spindled or stellate cells around the elongated glands. At the other end of the spectrum, mammary-type ductal carcinomas are rare malignant tumours of the anogenital mammary-like glands. Histologically, the majority of the published cases have shown an infiltrative pattern, which in some cases, is accompanied by an in situ component. It is important to recognize anogenital mammary-like glands, as neoplastic change can be mistaken for metastatic breast cancer, which will lead to inappropriate investigation and treatment. These cases aim to raise awareness among dermatologists of the entity of anogenital mammary-like glands and the neoplastic changes that can occur in them. DP02 Diagnostic utility of the Pigmented Lesion Assay in an academic setting P. Shah, L. Fried, J. Stein, T. Liebman, D. Polsky and S. Meehan New York University Grossman School of Medicine and Laura and Isaac Perlmutter Cancer Center, New York City, NY, USA Current clinical studies of the Pigmented Lesion Assay (PLA; DermTech, La Jolla, CA, USA) are largely supported by DermTech and are thus subject to potential bias. These studies demonstrate a > 99% negative predictive value (NPV) (Ferris LK, Rigel DS, Siegel DM et al. Impact of clinical practice of a non-invasive gene expression melanoma rule-out test: 12month follow-up of negative test results and utility data from a large US registry study. Dermatol Online J 2019; 25: 13030/ qt61w6h7mn), 95% sensitivity, 91% specificity and a 93% positive predictive value (PPV) of a double-positive LINC/ PRAME gene expression result (Ferris LK, Gerami P, Skelsey MK et al. Real-world performance and utility of a noninvasive gene expression assay to evaluate melanoma risk in pigmented lesions. Melanoma Res 2018; 28: 478–82). We aimed to validate the diagnostic performance of PLA in a real-world study of patients in an academic medical setting. We hypothesized that PLA would have a lower specificity and PPV than previously reported results. We conducted a retrospective cohort study of patients in which the PLA was used to assist the evaluation of a lesion suspicious for melanoma. PLA-positive lesions proceeded to skin biopsy and PLA-negative lesions were managed with follow-up monitoring; PLA-indeterminate lesions (usually due to insufficient sampling) were managed as per the clinical judgement of the dermatologist. PLA lesions with at least 6 months of follow-up were included. PLA sensitivity, specificity, PPV and NPV were evaluated using histopathological examination and follow-up clinical evaluation as ground truth. The study population included 122 cases (57 4% were female). Mean (SD) age was 52 2 (16 3) years. Forty-four patients (36 1%) had a history of melanoma, 38 (31 2%) had a history of keratinocyte cancer, 73 (59 8%) had a history of atypical naevi, 24 (19 7%) had a family history of melanoma and 85 had > 25 naevi on examination (69 7%). Ninety-eight cases (80 3%) were evaluated by pigmented lesion experts. Six cases (4 9%) were melanoma and two (1 6%) were keratinocyte cancers. Fifteen cases (12 2%) had an indeterminate PLA result and 17 cases (13 9%) were lost to follow-up. PLA sensitivity was 80% (n = 4/5), specificity was 82% (n = 71/ 87), PPV was 20% (n = 4/20) and NPV was 99% (n = 71/ 72). Double-positive (LINC and PRAME) PPV was 22% (n = 2/ 9), LINC-only PPV was 11% (n = 1/9) and PRAME-only PPV was 50% (n = 1/2). Median time to follow-up for PLAlesions was 161 days. In contrast to previously published reports, in an academic medical setting with more high-risk patients for melanoma than typical community settings, PLA