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P7. Multiple Wiesner nevi (BAP-omas): A case report

Giedrius Salkus(1), Mary Holten Hansen(1), Lykke Grubach(1), Inge Søkilde Pedersen(2), Niels Kren Veien(3), Artur Zembowicz(4)

(1) Institute of Pathology, Aalborg University Hospital, Denmark; (2) Section of Molecular Diagnostics, Department of Clinical Biochemistry, Aalborg University Hospital, Denmark; (3) Dermatology Clinic, Fyrkildevej, Aalborg,Denmark; (4) Dermatopathology Consultations,LLC and Tufts Medical School, Boston,Massachusetts, USA

Introduction: Wiesner nevus or BAP’oma is a recently described entity characterized by distinct histological features and BRAF and BAP1 germline mutations with a predisposition to internal neoplasia. We describe a patient with multiple Wiesner nevi.

Material and methods: The skin specimens were processed according to the routine histology protocol. Histology sections were stained with Hematoxylin & Eosin. Immunohistochemical reactions for Ki67/MLA, HMB45, p16 and BRAF V600E were carried out and BRAF mutational status was assessed by PCR as well. Sequencing of BAP1 was carried out for two lesions and on perilesional skin of one of the lesions.

Results: A 29-year-old female presented with multiple skin lesions on her trunk and extremities. The lesions were clinically consistent with Spitz nevi. Five lesions on the left shoulder, the left side of the back, the trunk and the hip were excised over a period of two years. Microscopy of all the lesions revealed unusual dermal and junctional melanocytic proliferation with epithelioid features, a lack of maturation and up to 1-2 dermal mitoses pr. mm2. A BRAF V600E mutation was identified in the lesions. A BAP1 T351Lfs*11 mutation was identified in both lesions and perilesional skin.

Discussion and conclusion: Wiesner nevus or BAP’oma is a challenging diagnosis for clinicians and dermatopathologists because of atypical clinical and unusual histological features. Some investigators consider Wiesner nevi a premalignant condition. However, it is unlikely that malignant melanoma would develop in a Wiesner nevus. It is important to recognize the Wiesner nevus as a marker for germline BAP1 mutation. The mutation is associated with cancer susceptibility syndrome with a predisposition for malignant mesothelioma, uveal malignant melanoma and some other tumours. It is, therefore, important to provide the patient with an individual follow-up plan. Although sporadic Wiesner nevi may occur, multiple lesions raise a suspicion of syndrome association. In such cases, BAP1 mutation can be detected in other tissue. We recommended that the patient be seen at a department of clinical genetics.

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