Dermatology: Practical and Conceptual Image Letter | Dermatol Pract Concept. 2024;14(1):e2024019 1 Giant Primary Cutaneous Follicle Centre B-Cell Lymphoma Alberto Corrà1, Isabella Ciardetti1, Andrea Gemignani1, Eleonora Gherardi1, Nicola Pimpinelli1, Vieri Grandi1 1 Department of Health Sciences, Section of Dermatology, University of Florence, P. Palagi Hospital, Florence, Italy Citation: Corrà A, Ciardetti I, Gemignani A, Gherardi E, Pimpinelli N, Grandi V. Giant Primary Cutaneous Follicle Centre B-Cell Lymphoma. Dermatol Pract Concept. 2024;14(1):e2024019. DOI: https://doi.org/10.5826/dpc.1401a19 Accepted: May 29, 2023; Published: January 2024 Copyright: ©2024 Corrà et al. This is an open-access article distributed under the terms of the Creative Commons Attribution- NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original authors and source are credited. Funding: None. Competing Interests: None. Authorship: All authors have contributed significantly to this publication. Corresponding Author: Grandi Vieri, Department of Health Sciences, Section of Dermatology, University of Florence, P. Palagi Hospital, Viale Michelangelo 41, 50141, Florence, Italy. E-mail: Vieri.grandi@unifi.it Case Presentation A 67-year-old man presented with firm, smooth, violaceous scalp nodules in the frontal-parietal region, which had been present for 4 years. The lesions exhibited slow growth and had merged to form a mass with telangiectasia, necrosis, ulceration, and crusting. Histological evaluation showed a dense follicular proliferation separated from the epidermis by a grenz zone, consisting of enlarged centrocytes intermixed with centroblasts. Immunohistochemistry was positive for Bcl-6, CD20, CD79a, PAX-5, while CD10, Bcl-2, CD34, CD38, CD68, IRF4/MUM1, CD4 were negative. Subsequent staging CT scan showed infiltration of the periosteum, bone, and dura mater, but no evidence of nodal or extracutane- ous visceral disease was found. A bone marrow biopsy did not reveal any signs of lymphoma. We made a diagnosis of primary cutaneous follicle center B-cell lymphoma (PCFCL). The patient was treated with the R-CHOP (rituximab, cy- clophosphamide, doxorubicin, vincristine and prednisone) regimen and achieved complete remission after 3 cycles. No relapses were observed during 18 months of follow-up. Teaching Point PCFCL accounts for 12% of cutaneous lymphomas and typ- ically occurs between the ages of 50 and 70 [1]. It manifests as slow-growing erythematous papules, plaques, or tumors primarily on the head-neck region or trunk. Histologically, PCFCL is characterized by the prolifer- ation of centrocytes, centroblasts, and a few reactive lym- phocytes. The immunophenotype of neoplastic cells shows positive expression of B‐cell markers such as CD20, CD79a, and Bcl‐6, while lacking CD5 or CD43 expression, which distinguishes it from systemic follicular lymphomas. These markers are also helpful in differentiating PCFCL from primary cutaneous diffuse large B-cell lymphoma, leg type (which is positive for Bcl-2 and MUM1) and primary cuta- neous marginal zone lymphoma (which is positive for Bcl-2 but negative for Bcl-6 and CD10) [2]. Although PCFCL has an excellent prognosis, long- standing untreated masses can invade deeper structures, leading to in- creased morbidity and mortality. Nevertheless, even bulky and neglected disease can show rapid responses to treatment. 2 Image Letter | Dermatol Pract Concept. 2024;14(1):e2024019 References 1. Willemze R, Cerroni L, Kempf W, et al. The 2018 update of the WHO-EORTC classification for primary cutaneous lympho- mas. Blood. 2019;133(16):1703-1714. DOI: 10.1182/blood -2018-11-881268. PMID: 30635287. PMCID: PMC6473500. 2. Skala SL, Hristov B, Hristov AC. Primary Cutaneous Follicle Center Lymphoma. Arch Pathol Lab Med. 2018;142(11):1313- 1321. DOI: 10.5858/arpa.2018-0215-RA. PMID: 30407851. Figure 1. (A,B) Pictures of the giant mass of the scalp affecting the fronto-parietal area, in frontal (A) and lateral (B) view. (C) Detail of the scalp mass. It is deducible that the mass resulted from the confluence of nodules, as an isolated tumor is visible in the lower part of the pic- tures. Telangiectasia, crusting, necrosis with ulceration and fibrin deposits are also appreciable.