Lymphocytic Lobular Panniculitis: A Diagnostic Challenge

Histological evidence of a lymphocytic lobular panniculitis is always a great diagnostic challenge. The possible diagnosis ranging from benign conditions, such as lupus panniculitis (LP), to indolent or aggressive types of T-cell lymphoproliferative disorders, such as subcutaneous panniculitis-like T-cell lymphoma (SPTL) and primary cutaneous γ/δ T-cell lymphoma (GDTCL). Integration between clinical, histological, and immunophenotypic features is necessary to obtain a definitive diagnosis. SPTL is a rare cutaneous lymphoma, accounting for <1% of all non-Hodgkin lymphomas. It is related to a favorable prognosis except for cases complicated by hemophagocytic syndrome, associated with a decrease in survival (5-year overall survival 46% compared to 91%) [1]. SPTL had previously been categorized into 2 distinct entities: the α/β subtype, characterized by a good prognosis, and the γ/δ subtype, with a more aggressive behavior. Later, the second subtype was reclassified as distinct entity in the group of rare disease by the name of GDTCL [2]. SPTL occurs frequently in young people and is characterized by subcutaneous nodules and plaques, which can be necrotic but rarely ulcerated (Fig. 1a). The extremities are typically involved. Systemic symptoms, such as fatigue, fever, or weight loss, may be present [3]. The lesions are characterized by a lipotropic infiltrate of predominant small/mediumsized pleomorphic T cells in the subcutaneous tissue, usually sparing the dermis and epidermis. Neoplastic cells, mixed with macrophages, tend to be localized around adipocytes, forming the typical “rimming” and “capping” images (Fig. 1b, c). The phenotype of the neoplastic cells is βF1+, CD3+, CD4–, CD8+, CD45RO+ (Fig. 1d), and they express cytotoxic granules (TIA-1, granzyme, and perforin). Epstein-Barr virus (EBV) is usually not found. Analysis of the T-cell receptor (TCR) rearrangement by polymerase chain reaction (PCR) shows clonal proliferation of the T cells [1]. Received: January 3, 2018 Accepted: January 10, 2018 Published online: February 15, 2018