Primary Cutaneous Follicle Center Lymphoma Clear Cell Variant: Expanding the Spectrum of Cutaneous Clear Cell Neoplasms

Abstract: Primary cutaneous follicle center lymphoma is the most frequent cutaneous B-cell lymphoma despite the fact that is an uncommon disease. Mild biological behavior and good prognosis characterized this neoplasm with a low aggressiveness compared with classic nodal follicular lymphoma (FL). Rare histological variants have been described. We present the case of a 72-year-old man who underwent surgery for a cutaneous nodule on his left scapula. The biopsy showed a dermal clear cell proliferation arranged in a nodular and diffuse pattern. The cells stained positive for CD20 and Bcl-6 supporting B-cell follicular differentiation. The final diagnosis was "primary cutaneous follicle center lymphoma" with "clear cell changes" according to the 2016 World Health Organization classification of lymphoid neoplasms. Additional tests to rule out a systemic involvement were performed. The prognosis was favorable with a disease-free survival of 7 years after complete surgical excision. It has been assumed that cutaneous tumors composed of clear cells may have an epithelial, melanocytic, adnexal, mesenchymal, or metastatic origin. The correct histopathological diagnosis required immunohistochemistry and even molecular techniques. To the best of our knowledge, this is the first report of a cutaneous clear cell lymphoma and of a FL with clear cell features. Our findings provide evidence that the heterogeneity of FL is greater than previously thought and expand the spectrum of differential diagnosis in cutaneous clear cell neoplasms. Dermatopathologists should be aware of this entity and should comprise a PanB marker in their first- or second-line immunohistochemistry for the correct diagnosis of a dermal clear cell proliferation. Correspondence: Angelo Cassisa, MD, Pathology Unit, Carlo Poma Hospital of Mantova, Str. Lago Paiolo, n. 10, 46100 Mantova, Italy (e-mail: angelo.cassisa@asst-mantova.it). Internal funding from Department of Clinical Services has been used in part for study-related facilities. The authors declare no conflicts of interest. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.

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