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International audience; YAP1-NUTM1 fusion transcripts have been recently reported in poroma and porocarcinoma. NUTM1 translocation can be screened by nuclear protein in testis (NUT) immunohistochemistry in various malignancies, but its diagnostic performance has not been thoroughly validated on a large cohort of cutaneous epithelial neoplasms. We have evaluated NUT immunohistochemical expression in a large cohort encompassing 835 cases of various cutaneous epidermal or adnexal epithelial neoplasms. NUT expression was specific to eccrine poromas and porocarcinoma, with 32% of cases showing NUT expression. All other cutaneous tumors tested lacked NUT expression, including mimickers such as seborrheic keratosis, Bowen disease, basal cell carcinoma, squamous cell carcinoma, Merkel cell carcinoma, nodular hidradenoma, and all other adnexal tumors tested. Remarkably, NUT expression was more frequent in a distinct morphologic subgroup. Indeed, 93% of poroid hidradenoma (dermal/subcutaneous nodular poroma, 13/14) and 80% of poroid hidradenocarcinoma cases (malignant poroid hidradenoma, 4/5) showed NUT expression, in contrast to 17% and 11% of classic poroma (4/23) and porocarcinoma cases (4/35), respectively. RNA sequencing of 12 NUT-positive neoplasms further confirmed the presence of a YAP1-NUTM1 fusion transcript in all cases, and also an EMC7-NUTM1 gene fusion in a single case. In the setting of a cutaneous adnexal neoplasm, nuclear expression of NUT accurately and specifically diagnosed a specific subgroup of benign and malignant poroid tumors, all associated with a NUTM1 fusion, which frequently harbored a poroid hidradenoma morphology.

Primary angiosarcoma of the breast is a rare malignant tumour that presents in young women as a painless mass or a sensation of fullness in the breast. To report two cases of primary breast angiosarcoma presenting with unusual and misleading cutaneous lesions. A clinical investigation including ultrasound, MRI and histological examination. In the first patient, the lesion appeared as a superficial, acquired angioma; in the second as an indolent superficial haematoma. This type of primary presentation is exceptional and the benign appearance of the lesion, combined with a lack of breast mass, is misleading. The benign appearance and the pathological aspect of these lesions can lead to misdiagnosis. Comparison of clinical and pathological data is necessary to prevent delay in diagnosis. We believe that all acquired angiomatous lesions developing on the breasts of young women should raise suspicion of angiosarcoma.

Necrotizing Infundibular Crystalline Folliculitis (NICF) is rare entity of unknown pathogenesis presenting as follicular crystalline papules arising in seborrheic areas. We report 2 cases of NICF in patients under targeted therapy for metastatic adenocarcinoma. In one case, the lesions reappeared cyclically every 3 weeks after each injection and in the other case, lesions persisted until disruption of the continuous oral therapy. Punch-biopsies demonstrated folliculitis with a plugging crystalline material associated with either bacteria or yeast. These are the first descriptions of drug-induced NICF.

AIMS: Aggressive epidermotropic cutaneous CD8+ lymphoma is currently afforded provisional status in the WHO classification of lymphomas. An EORTC Workshop was convened to describe in detail the features of this putative neoplasm and evaluate its nosological status with respect to other cutaneous CD8+ lymphomas.METHODS & RESULTS: Sixty-one CD8+ cases were analysed at the workshop; clinical details, often with photographs, histological sections, immunohistochemical results, treatment and patient outcome were discussed & recorded. Eighteen cases had distinct features and conformed to the diagnosis of aggressive epidermotropic cutaneous CD8+ lymphoma. The patients typically present with widespread plaques and tumours, often ulcerated and haemorrhagic, and have striking pagetoid epidermotropism histologically. A CD8+ CD45RA+ CD45RO- CD2- CD5- CD56- phenotype, with 1 or more cytotoxic markers was found in 7/18 with a very similar phenotype in the remainder.. The tumours seldom involve lymph nodes but mucosae and central nervous system involvement are not uncommon. The prognosis is poor, with a median survival of 12 months. Examples of CD8+ mycosis fungoides, lymphomatoid papulosis and Woringer-Kolopp presented the typical features well documented in the CD4+ forms of those diseases.CONCLUSIONS: Aggressive Epidermotropic Cutaneous CD8+ Lymphoma is a distinct lymphoma that warrants inclusion as a distinct entity in future revisions of lymphoma classifications. This article is protected by copyright. All rights reserved.

e14677 Background: BRAF V600E mutations are rare in colorectal cancers, being present in less than 10% of the cases. The prognosis of BRAF mutant tumors seems heterogeneous but usually poor, especi...