Primary cutaneous follicular helper T‐cell lymphoma: diagnostic pitfalls of this new lymphoma subtype

• Published in: Journal of cutaneous pathology 2013-10, Vol.40 (10), p.903-908
• Main Authors: Buder, Kristina, Poppe, Lidía M., Bröcker, Eva B., Goebeler, Matthias, Rosenwald, Andreas, Geissinger, Eva, Kerstan, Andreas
• Format: Article
• Language: English
• Subjects: Antigens, Differentiation - metabolism; B-cell lymphoma; bexarotene; Biomarkers, Tumor - metabolism; Diagnosis, Differential; electron beam; Female; follicular helper T‐cell lymphoma; Humans; Lymphoma, B-Cell - classification; Lymphoma, B-Cell - drug therapy; Lymphoma, B-Cell - pathology; Lymphoma, T-Cell, Cutaneous - classification; Lymphoma, T-Cell, Cutaneous - drug therapy; Lymphoma, T-Cell, Cutaneous - metabolism; Lymphoma, T-Cell, Cutaneous - pathology; Middle Aged; PUVA Therapy; Skin Neoplasms - classification; Skin Neoplasms - drug therapy; Skin Neoplasms - pathology; T-Lymphocytes, Helper-Inducer - metabolism; T-Lymphocytes, Helper-Inducer - pathology; treatment‐refractory lymphoma
• ISSN: 0303-6987; 1600-0560
• DOI: 10.1111/cup.12204

The recently proposed entity of cutaneous follicular helper T (TFH) cell lymphoma (CTFHCL) harbors distinct clinical and histopathologic features. Here, diagnostic pitfalls are exemplified in a case report and by review of the literature. A 45‐year‐old patient developed rapidly growing nodules and plaques on upper arms and buttocks, which were initially misdiagnosed as primary cutaneous follicle center B‐cell lymphoma (CFCL). Consequently, systemic therapy with rituximab failed and consecutive skin biopsies revealed CTFHCL (CD3+CD4+CD10+PD‐1+bcl6+ICOS+CXCL13+). Interestingly, the prima vista PD‐1‐positive and CD10‐positive tumor cells lost PD‐1 expression in follow‐up biopsies while retaining CD10, ICOS and CXCL13 expression. All biopsy specimens displayed an identical clonal T‐cell population. Initially, nodules were controlled by local radiotherapy and oral psoralen combined with ultraviolet A (PUVA) therapy. However, disease recurred and progressed rapidly with disseminated nodules. Treatment with bexarotene, methotrexate and polychemotherapy failed to stop disease progression. Finally, modified total skin electron beam radiation resulted in complete remission. Disease stabilized on maintenance therapy with bexarotene in combination with ultraviolet A (UVA) therapy. The case highlights that because of concomitant B‐cell stimulation, CTFHCL clinicopathologically is prone to be mistaken for CFCL. Importantly, CTFHCL might lose PD‐1 while retaining CD10 expression in later stages, which may lead to confusion in distinguishing CTFHCL from CFCL.