Useful Parameters for Distinguishing Subcutaneous Panniculitis-like T-Cell Lymphoma From Lupus Erythematosus Panniculitis

Abstract

Some cases of subcutaneous panniculitis-like T-cell lymphoma (SPTCL) and lupus erythematosus panniculitis (LEP) demonstrate clinical and histopathologic overlap, raising the possibility that they represent opposite ends of a disease spectrum. SPTCL, however, is typically associated with greater morbidity and risk for hemophagocytic lymphohistiocytosis (HLH); therefore, diagnostic distinction is clinically important. We present the histopathologic, immunophenotypic, and molecular findings with long-term clinical follow-up of 13 patients with SPTCL (median, 64 mo follow-up) and 7 with LEP (median, 50 mo follow-up) in our multidisciplinary cutaneous oncology clinic. Six SPTCL patients developed HLH, including 2 under the age of 21 years. In the SPTCL group, 2 of 13 patients died of disease. In contrast, we had no mortality or development of HLH in our LEP cohort. We demonstrate that a limited panel (Ki-67, CD3, CD4, and CD8 immunostains) reveals foci of "Ki-67 hotspots" enriched in cytotoxic atypical CD8+ T cells in SPTCL. Ki-67 hotspots were not identified in LEP, thus aiding the distinction of SPTCL from LEP. Lymphocyte atypia combined with adipocyte rimming of CD8+ T cells within Ki-67 hotspots was also highly specific for the diagnosis of SPTCL. Hyaline lipomembranous change, B-cell aggregates, plasmacytoid dendritic cell clusters, and plasma cell aggregates favored the diagnosis of LEP but were identified in some cases of SPTCL including patients with HLH. We confirm that SPTCL and LEP can show significant histologic overlap, suggest a role for high-throughput sequencing in confirming neoplastic clones, and introduce the concept of SPTCL "Ki-67 hotspots" in evolving disease.

Clinicopathologic, immunophenotypic, and molecular analysis of subcutaneous panniculitis‐like T‐cell lymphoma: A retrospective study in a tertiary care center

“…Of note, Ki‐67 staining was found to be as high as 50% to 90% positive in atypical cytotoxic CD8 + T‐cells in our study. These findings were similar to LeBlance et al study which reported >30% Ki‐67 staining positive, confirming Ki‐67 staining is highly specific for diagnosis of SPTL as opposed to LEP.…”

“…To exclude coexisting cutaneous lupus erythematosus, mucin, and plasmacytoid dendritic cells were stained and show negative results . Although CD8 + , BF1 + , granzyme B + , and monoclonal T‐cell clone are typical findings for diagnosis of SPTL, they are also present in lupus panniculitis …”

“…The following histopathological characteristics were reviewed: distribution and pattern of infiltrate, cytological composition (lymphocytes, neutrophils, eosinophils, and plasma cells), cytophagocytosis, angioinvasion, and fat necrosis. For plasma cells, we defined the term “significant proportion of plasma cells” if focal aggregation of plasma cells were more than or equal to 10 cells/high power field …”

Epidemiology of primary cutaneous γδ T‐cell lymphoma and subcutaneous panniculitis‐like T‐cell lymphoma in the U.S.A. from 2006 to 2015: a Surveillance, Epidemiology, and End Results‐18 analysis

“…including mycosis fungoides (MF), although the significance of low levels of gamma/delta TCR expression is controversial . Overlap of panniculitis‐like lymphomas with lupus panniculitis, MF and peripheral T‐cell lymphoma not otherwise specified may create additional diagnostic ambiguity …”

Immunohistochemistry reveals an increased proportion of MYC‐positive cells in subcutaneous panniculitis‐like T‐cell lymphoma compared with lupus panniculitis

“…In contrast to LEP, the lobular panniculitis of SPTCL typically shows a predominance of CD8+ T cells with a cytotoxic phenotype as demonstrated by expression of TIA‐1, perforin and granzyme. The neoplastic T lymphocytes in SPTCL also show a higher proliferation index than LEP which can be highlighted by immunostaining for Ki‐67 . Demonstration of T‐cell receptor clonality by high‐throughput sequencing can also support the diagnosis of SPTCL .…”