Characterization of Primary and Secondary Cutaneous B-Cell Lymphomas: A Population-Based Study of 4758 Patients

INTRODUCTION/BACKGROUND

Cutaneous B-cell lymphomas are a heterogeneous group of rare malignancies whose specific site tropisms and site-specific survival have not been well documented. In this study, we seek to investigate the frequency and survival for primary and secondary cutaneous MZL (pcMZL and scMZL), primary and secondary cutaneous FCL (pcFCL and scFCL), and primary and secondary cutaneous DLBCL (pcDLBCL and scDLBCL) to better understanding their prognosis and natural history.

MATERIALS AND METHODS

A total of 4758 cases of CBCL diagnosed between 1975 and 2016 were identified in the SEER-18 database. Statistical analysis was performed to identify the frequency of location and survival.

RESULTS

pcMZL was disproportionately likely to present on the face and upper limb while those of scMZL approximated the expected ratios based on body surface area. pcFCL and scFCL were more likely to present on the face and scalp/neck. pcDLBCL and scDLBCL were more likely to present on the face, scalp/neck, and lower limb. Patients with systemic MZL or FCL, but not DLBCL, had significantly better survival than those diagnosed in the skin than at other sites.

CONCLUSIONS

All of these lymphomas demonstrate site-specific tropisms and survival. Molecular characterization of cutaneous lymphomas with analyses of tumor microenvironment are the next steps in understanding disease biology.

Cell-of-origin classification using the Hans and Lymph2Cx algorithms in primary cutaneous large B-cell lymphomas

Primary cutaneous diffuse large B-cell lymphoma, leg type (PCDLBCL-LT) and primary cutaneous follicle center lymphoma with a diffuse population of large cells (PCFCL-LC) are both primary cutaneous B-cell lymphomas with large-cell morphology (CLBCL) but with different clinical characteristics and behavior. In systemic diffuse large B-cell lymphoma, not otherwise specified (DLBCL-NOS), gene-expression profiling (GEP) revealed two molecular subgroups based on their cell-of-origin (COO) with prognostic significance: the germinal center B-cell-like (GCB) subtype and the activated B-cell-like (ABC) subtype. This study investigated whether COO classification is a useful tool for classification of CLBCL. For this retrospective study, 51 patients with PCDLBCL-LT and 15 patients with PCFCL-LC were analyzed for their COO according to the immunohistochemistry-based Hans algorithm and the NanoString GEP-based Lymph2Cx algorithm. In PCFCL-LC, all cases (100%) classified as GCB by both Hans and Lymph2Cx. In contrast, COO classification in PCDLBCL-LT was heterogeneous. Using Hans, 75% of the PCDLBCL-LT patients classified as non-GCB and 25% as GCB, while Lymph2Cx classified only 18% as ABC, 43% as unclassified/intermediate, and 39% as GCB. These COO subgroups did not differ in the expression of BCL2 and IgM, mutations in MYD88 and/or CD79B, loss of CDKN2A, or survival. In conclusion, PCFCL-LC uniformly classified as GCB, while PCDLBCL-LT classified along the COO spectrum of DLBCL-NOS using the Hans and Lymph2Cx algorithms. In contrast to DLBCL-NOS, the clinical relevance of COO classification in CLBCL using these algorithms has limitations and cannot be used as an alternative for the current multiparameter approach in differentiation of PCDLBCL-LT and PCFCL-LC.

The molecular landscape and other distinctive features of primary cutaneous follicle center lymphoma

Primary cutaneous follicle center lymphoma (PCFCL) is distinguished from other follicular lymphomas (FLs) based on its clinicopathologic features including diminished CD10 and frequent lack of BCL2 rearrangements (R). Whether newer germinal center-associated markers would also be less commonly expressed and whether mutational studies would support its segregation from classic FL and FL subsets, including those which also typically lack BCL2R, are uncertain. To address these questions, 22 PCFCLs were stained for myocyte enhancer factor 2B (MEF2B) and human germinal center-associated lymphoma (HGAL), and targeted next-generation sequencing was performed with results compared to a meta-analysis of FL, pediatric-type FL (PTFL), low stage FL (LSFL) and other FL subsets. Selected fluorescence in situ hybridization studies were also performed. Although 27% of cases lacked CD10, all tested were MEF2B+ and HGAL+. The most common somatic mutations in the 12 to 19 analyzable PCFCL were TNFRSF14 (40%, plus 10% with 1p36 deletions), followed by CREBBP, TNFAIP3, KMT2D, SOCS1, EP300, STAT6, and FOXO1 (17-25%). Three of the most commonly mutated genes in FL (KMT2D, CREBBP, and BCL2) were significantly less commonly mutated in PCFCL than in FL, and TNFAIP was more commonly mutated with no difference for TNFRSF14 between PCFCL and FL or PTFL. CREBBP was also less frequently mutated than in LSFL but more frequently mutated than in PTFL. MAP2K1 mutations were much more common in PTFL (44% versus 0%). Two of 22 of the PCFCL had a BCL2 rearrangement and zero of 12 had a BCL6 rearrangement. These findings, while showing well-recognized and new shared features between PCFCL and other FL, highlight a distinctive mutational profile further supporting its recognition as a distinct entity.

Unusual Clinical Presentation of a Primary Cutaneous Follicle Center Lymphoma on the Scalp of a Middle-Aged Female: Case Report and Review of the Literature

Primary cutaneous follicle center lymphoma (PCFCL) is a rare type of indolent, low-grade cutaneous B-cell lymphoma with an excellent prognosis. It usually presents with erythematous nodules and plaques on the head, neck, or back. The diagnosis is primarily based on histopathology, immunohistochemistry, and molecular studies. We describe a case of PCFCL causing a well-defined alopecic atrophic patch. The patch developed in the area of a large subcutaneous nodule that regressed after treatment with rituximab infusion. We hypothesize that the alopecia could have been caused by pressure.

Primary Cutaneous Follicle Center Lymphoma of the Eyelid: A Case Report and Review of the Literature in Light of Recent Changes to the WHO Classification of Lymphoid Neoplasms

Primary cutaneous follicle center lymphoma (PCFCL) is a unique entity that represents up to 11% of all cutaneous lymphomas. PCFCL is associated with an indolent course and excellent 5-year survival rates, but can progress to secondary systemic involvement if left untreated. Histopathologic features of PCFCL can vary depending on the size, duration, and clinical stage of the lesion, making diagnosis somewhat challenging. Here, we present a case of a 50-year-old woman with an eyelid lesion that was initially classified as an inflamed cyst based on biopsy, but 1 year later, was determined to be PCFCL after repeat biopsy revealed different histology. In light of the recent changes to the WHO classification of lymphoid neoplasms, we review the unique clinical and histopathologic features of PCFCL that distinguish it from other more aggressive forms of cutaneous lymphoma in terms of course, prognosis, and management.

Primary Cutaneous B-cell Lymphomas

B-cell lymphomas represent approximately 20% to 25% of primary cutaneous lymphomas. Within this group, most cases (>99%) are encompassed by 3 diagnostic entities: primary cutaneous marginal zone lymphoma, primary cutaneous follicle center lymphoma, and primary cutaneous diffuse large B-cell lymphoma, leg type. In this article, the authors present clinical, histopathologic, immunophenotypic, and molecular features of each of these entities and briefly discuss the rarer intravascular large B-cell lymphoma.

Primary cutaneous B-cell lymphomas with large cell predominance-primary cutaneous follicle center lymphoma, diffuse large B-cell lymphoma, leg type and intravascular large B-cell lymphoma

In this review, we present clinical features and detailed histopathologic, immunologic, and molecular information regarding primary cutaneous follicle center lymphoma and primary cutaneous diffuse large B-cell lymphoma, leg type which together represent two of the three most common types of primary cutaneous B-cell lymphoma recognized in the current WHO classification system.^1,2 Overall, B-cell lymphomas represent 19-27% of primary cutaneous lymphomas in most large European and American studies^3-6 and together, primary cutaneous follicle center lymphoma and primary cutaneous diffuse large B-cell lymphoma, leg type account for approximately 2/3 to ¾ of these cases.^5,7-11 Both subtypes can contain a high content of large B-lymphocytes, although most cases of primary cutaneous follicle center lymphomas exhibit a range in cell size and cytology. Intravascular large B-cell lymphoma, a less commonly-encountered EBV-negative primary cutaneous B-cell lymphoma composed of large cells, will be more briefly discussed in this report as well.

TOX expression in cutaneous B-cell lymphomas

Thymocyte selection-associated high-mobility group box (TOX) is aberrantly expressed in cutaneous T-cell lymphomas. In a recent study, TOX expression was noted unexpectedly in the follicle center (germinal center) B-cells of reactive lymph nodes and tonsils, used as external controls. To evaluate whether TOX is also expressed by cutaneous B-cell lymphomas, TOX immunohistochemistry was performed on skin biopsies of 44 patients with primary and secondary cutaneous B-cell proliferations. TOX was expressed not only in the reactive follicle center cells of lymph nodes, tonsils, cutaneous lymphoid hyperplasia, and primary cutaneous marginal zone lymphomas, but also by the neoplastic follicle center cells of 16/17 patients with primary cutaneous follicle center lymphoma (PCFCL) and 7/7 patients with cutaneous manifestations of systemic follicular lymphoma (FL). Notably, TOX showed a very similar expression pattern as BCL6, a marker of germinal center B-cells. In 4/10 patients with a BCL6(+) primary cutaneous diffuse large B-cell lymphoma, leg type (PCDLBCL,LT) and in 2/2 patients with a secondary cutaneous BCL6(+) diffuse large B-cell lymphoma (DLBCL), TOX was expressed by more than 50 % of the neoplastic B-cells. In contrast, in 3/3 BCL6(-) PCDLBCL,LT, TOX was completely negative or weakly expressed by a minor proportion of the neoplastic B-cells. In conclusion, TOX is expressed not only by neoplastic T-cells, but also by both reactive and neoplastic follicle center (germinal center) B-cells and a proportion of BCL6(+) PCDLBCL,LT and secondary cutaneous BCL6(+) DLBCL. The functional significance of TOX expression in reactive and neoplastic B-cells remains to be elucidated.

Primary cutaneous follicle center lymphoma associated with an extracutaneous dissemination: a cytogenetic finding of potential prognostic value

OBJECTIVES

Cytogenetic studies on cutaneous lymphomas are rare, and very little is known about their prognostic value. We present a rare case of primary cutaneous follicle center lymphoma (PCFCL) with a complex translocation presenting with cutaneous and extracutaneous dissemination in the lymph node.

METHODS

Morphologic, immunohistochemical, conventional cytogenetic, and fluorescence in situ hybridization (FISH) studies were performed on this patient.

RESULTS

A combination of cytogenetic and FISH analysis identified a complex novel four-way t(2;14;9;3) (p11.2;q32;p13;q27) translocation involving rearrangements of BCL6, immunoglobulin light and heavy chain genes, and an unknown gene on 9p.

CONCLUSIONS

Our report elaborates the morphologic and immunohistochemical features in combination with cytogenetic and molecular cytogenetic analysis of PCFCL, which provide additional insight into the clinical and biologic behavior of this lesion.

Diagnostic and prognostic value of BCL2 rearrangement in 53 patients with follicular lymphoma presenting as primary skin lesions

OBJECTIVES

To study the diagnostic value of BCL2 rearrangement in follicle center lymphoma (FCL) presenting as primary skin lesions, evaluate its prevalence and the prognostic value in primary cutaneous FCL (PCFCL), and assess prognostic factors in PCFCL.

METHODS

Fifty-three patients with a cutaneous presentation of FCL without a history of nodal lymphoma were selected retrospectively. Clinical and histologic data were collected together with staging and follow-up data. A fluorescence in situ hybridization (FISH) test for BCL2 split probes was performed on skin biopsy specimens.

RESULTS

Initial staging procedures identified 47 PCFCLs and six cases of secondary skin involvement of FCL (SSIFCL). FISH detected seven cases carrying a BCL2 rearrangement: four (8.5%) of 47 PCFCLs and three (50%) of six SSIFCLs. These seven cases coexpressed BCL2 and CD10. In PCFCL, cutaneous relapse rate was 42.6%. A small/medium centrocytic cell population was associated with a higher probability of skin relapse in univariate (P = .008) and multivariate (P = .028) analysis, and BCL2 rearrangement detection was associated with secondary extracutaneous spreading (P = .05).

CONCLUSIONS

We observed that BCL2 rearrangement in PCFCL is rare, associated with initial positivity of staging (diagnostic value) or with secondary extracutaneous spreading (prognostic value). In selected cases with BCL2-CD10 coexpression, FISH testing could detect patients with poor outcome and require closer monitoring.