Lymphoid aggregates in desmoplastic melanoma have features of tertiary lymphoid structures

Abstract

Desmoplastic melanomas (DM) have unique and challenging clinical presentations and histomorphology. A characteristic feature is the presence of scattered lymphoid aggregates. However, the nature of these aggregates is not defined. We hypothesized that they may be tertiary lymphoid structures (TLS), and may be associated with programmed death ligand 1 (PD-L1) expression. We searched our tissue database for 'pure' DMs and for scars as control tissues, collected clinical information, and reviewed H&E histology. We performed multispectral imaging after staining for CD8, CD20, PNAd, FoxP3, CD83, and Ki67, and assessed PD-L1 expression by immunohistochemistry. Pure DM samples were evaluable in 11 patients. All had desmoplastic stroma and lymphoid aggregates on H&E. The lymphoid aggregates of eight of the 11 (72%) DM samples and only three of the 11 scars contained features of TLS, defined as distinct clusters of B cells and CD8 T cells, CD83 dendritic cells in T-cell zones, and PNAd vasculature resembling high endothelial venules. PD-L1 was expressed by at least 1% of melanoma cells in six and by at least 5% of immune cells in 10 of the 11 DM samples. We found that most lymphoid aggregates in DM are organized, classical TLS. PD-L1 expression was detected in most cases and was highest in two cases of DM with TLS. However, low PD-L1 expression in some cases suggests that some DM cells may be unresponsive to interferon-γ. TLS support antigen presentation and T-cell responses in chronic inflammation and cancer. Their presence in DM likely reflects an adaptive immune response, which may be enhanced with immune therapies.

STING agonist-based treatment promotes vascular normalization and tertiary lymphoid structure formation in the therapeutic melanoma microenvironment

“…CD45 + immune clusters surrounding PNAd + HEVs resembling bona-fide TLS 37 were identified as early as 5 days after initiating treatment with ADU S-100 ( figure 4B ). These therapy-induced TLS were richly infiltrated with CD11c + DCs and CD3 + T cells, resembling previously reported ‘non-classical’ TLS 38 ( figure 4C ). IFM analyzes did not, however, reveal significant B cell infiltrates in our specimens ( online supplemental figure S4B ); consistent with our observed lack of Cxcl13 expression in the TME of ADU S-100 treated animals ( figure 4A ).…”

“…[59][60][61][62] Regardless of the ultimate role for B cells in a therapeutic TLS paradigm, it is noteworthy that in humans, the presence of either classical/mature or non-classical (ie, B-deficient) TLS in the TME correlates with improved patient outcome when compared with patients with tumors that fail to exhibit TLS. 38 While our studies were not specifically designed to identify mechanisms underlying resistance to i.t.-delivered STING agonist-based monotherapy that may have led to modest clinical activity in early-phase clinical trials, we observed that the treatment of DCs with ADU S-100 resulted in the compensatory upregulation of several known regulatory molecules that would be expected to mediate anti-inflammatory activity and thereby limit the therapeutic anti-tumor immune response. Notably, we observed that PD-L1, Ptgs2/COX2, Ptges and Arg2 expression were strongly upregulated on STING-activated DCs, suggesting these APCs may not mediate optimal/sustained immunostimulatory activity in vivo (online supplemental figure S6).…”

“… 59–62 Regardless of the ultimate role for B cells in a therapeutic TLS paradigm, it is noteworthy that in humans, the presence of either classical/mature or non-classical (ie, B-deficient) TLS in the TME correlates with improved patient outcome when compared with patients with tumors that fail to exhibit TLS. 38 …”

Tertiary lymphoid structures in the era of cancer immunotherapy

“…The clinical impact of TLSs on responses to therapies has very recently been extended to other cancers and to immunotherapies (W.H.F., unpublished observations). It is interesting to note that a high proportion of desmoplastic melanomas exhibit TLSs 117 and that this tumour type also has a high response rate to PD1 blockade 118 .…”

Spindle cell melanoma coexisting with chronic lymphocytic leukemia/small lymphocytic lymphoma: a rare collision tumor in multiple sites

“…We found that these foci of lymphoid populations were pronounced and focally involving skin appendages. In most of DM cases, these aggregates show features of tertiary lymphoid structures that contain a mixed type of cell population including organized clusters of usual CD20 + B‐cells and CD8 + T‐cells with CD83+ dendritic cells in T‐cell zones 24 . However, CLL is composed of monotonous, small‐sized neoplastic lymphoid cells with clumped chromatin that typically express CD5, CD11c, CD19 (dim), CD20 (dim), CD23, CD22 (weak or negative), Bcl‐2, and monoclonal kappa or lambda Ig light chain 25 .…”