Imbalance of Circulating Follicular Regulatory and Follicular Helper T Cell Subpopulations Is Associated with Disease Progression and Serum CYFRA 21-1 Levels in Patients with Non-small Cell Lung Cancer

Objective This study aimed to investigate the changes of follicular helper T(TFH)and follicular regulatory T(TFR)cell subpopulations in patients with non-small cell lung cancer(NSCLC)and their significance.Methods Peripheral blood was collected from 58 NSCLC patients at different stages and 38 healthy controls.Flow cytometry was used to detect TFH cell subpopulation based on programmed death 1(PD-1)and inducible co-stimulator(ICOS),and TFR cell subpopulation based on cluster determinant 45RA(CD45RA)and forkhead box protein P3(FoxP3).The levels of interleukin-10(IL-10),interleukin-17a(IL-17a),interleukin-21(IL-21),and transforming growth factor-β(TGF-β)in the plasma were measured,and changes in circulating B cell subsets and plasma IgG levels were also analyzed.The correlation between serum cytokeratin fragment antigen 21-1(CYFRA 21-1)levels and TFH,TFR,or B cell subpopulations was further explored.Results The TFR/TFH ratio increased significantly in NSCLC patients.The CD45RA^(+)FoxP3^(int) TFR subsets were increased,with their proportions increasing in stages Ⅱ to Ⅲ and decreasing in stage IV.PD-1^(+)ICOS+TFH cells showed a downward trend with increasing stages.Plasma IL-21 and TGF-β concentrations were increased in NSCLC patients compared with healthy controls.Plasmablasts,plasma IgG levels,and CD45RA^(+)FoxP3^(int) TFR cells showed similar trends.TFH numbers and plasmablasts were positively correlated with CYFRA 21-1 in stages Ⅰ-Ⅲ and negatively correlated with CYFRA 21-1 in stage IV.Conclusion Circulating TFH and TFR cell subpopulations and plasmablasts dynamically change in different stages of NSCLC,which is associated with serum CYFRA 21-1 levels and reflects disease progression.

Clinicopathological features and prognosis assessment of extranodal follicular dendritic cell sarcoma

AIM: To establish a model for prognosis assessment of extranodal follicular dendritic cell (FDC) sarcoma.METHODS: Nine lesions were examined by routine and molecular approaches.Clinicopathological factors from the new cases and 97 reported cases were analyzed for their prognostic values.RESULTS: The current lesions were found in f ive male and four female patients,located mainly in the head and neck area and averaging 7.2 cm in size.Six patients had recurrence or metastasis and three remained free of disease.The 106 patients (male/female ratio,1.1:1) were aged from 9 to 82 years (median,44 years).The tumor sizes ranged from 1.5 to 21 cm (mean,7.4 cm).Abdominal/pelvic region was affected most frequently (43%).Surgical resection was performed in 100 patients,followed by radiation and/or chemotherapy in 35 of them.Follow-up data were available in 91 cases,covering a period of 3-324 mo (mean,27 mo;median,19 mo).Of the informative cases,38 (42%) had recurrence or metastasis,and 12 (13%) died of the disease.These tumors were classif ied histologically into lowand high-grade lesions.A size ≥ 5 cm (P = 0.003),highgrade histology (P = 0.046) and a mitotic count ≥ 5/10 HPF (P = 0.013) were associated with tumor recurrence.The lesions were def ined as low-,intermediateand high-risk tumors,and their recurrence rates were 16%,46% and 73%,and their mortality rates 0%,4% and 45%,respectively.CONCLUSION: Extranodal FDC tumors behave like soft tissue sarcomas.Their clinical outcomes are variable and can be evaluated according to their sizes and grades.

Follicular dendritic cell sarcoma of the liver:unusual presentation of a rare tumor and literature review

BACKGROUND:Hepatic follicular dendritic cell (FDC) sarcoma is an extremely rare neoplasm.Most commonly,FDC sarcoma presents as a solitary mass in lymph nodes,however,several extra-nodal locations have been identified.METHODS:We report a case of a 53-year-old female who presented with symptoms of abdominal pain,fever,anemia,and jaundice.After an extensive review of the literature,we have found only 12 cases of hepatic FDC sarcoma.RESULTS:The tumor was 11.5 cm in diameter and composed of spindle and epithelioid cells with ovoid nuclei and associated with mixed inflammatory infiltrate.Immunohistochemical stains were positive for CD35 and CD21.The patient underwent a left hepatic lobectomy.CONCLUSIONS:Liver follicular dendritic cell sarcoma is a very rare tumor.Most cases present with abdominal pain and weight loss,and most of them can be managed by hepatic resection with excellent short-term outcomes.

Deficiency of Tfh Cells and Germinal Center in Deceased COVID-19 Patients

Summary:The COVID-19 pandemic caused by SARS-CoV2 is characterized by a remarkable variation in clinical severity ranging from a mild illness to a fatal multi-organ disease.Understanding the dysregulated human immune responses in the fatal subjects is critical for management of COVID-19 patients and the pandemic.In this study,we examined the immune cell compositions in the lung tissues and hilar lymph nodes using immunohistochemistry on 6 deceased COVID-19 patients and 4 focal organizing pneumonia(FOP)patients who underwent lung surgery and served as controls.We found a dominant presence of macrophages and a general deficiency of T cells and B cells in the lung tissues from deceased COVID-19 patients.In contrast to the FOP patients,Tfh cells and germinal center formation were largely absent in the draining hilar lymph nodes in the deceased COVID-19 patients.This was correlated with reduced IgM and IgG levels compared to convalescent COVID-19 patients.In summary,our data highlight a defect of germinal center structure in deceased COVID-19 patients leading to an impaired humoral immunity.Understanding the mechanisms of this deficiency will be one of the key points for the management of this epidemic.

Intra-abdominal inflammatory pseudotumor-like follicular dendritic cell sarcoma associated with paraneoplastic pemphigus: A case report and review of the literature

BACKGROUD Follicular dendritic cell(FDC)sarcomas are rare neoplasms that occur predominantly in the lymph nodes.They can also occur extranodally.Extranodal FDC sarcomas most commonly present as solitary masses.Inflammatory pseudotumor(IPT)-like FDC sarcomas,a subcategory of FDC sarcomas,are rarer than other sarcoma subtypes.They are composed of spindle or ovoid neoplastic cells and exhibit an admixture of plasma cells and prominent lymphoplasmacytic infiltration.Paraneoplastic pemphigus(PNP),also known as paraneoplastic autoimmune multiorgan syndrome,is a rare autoimmune bullous disease that is associated with underlying neoplasms.PNP has a high mortality,and its early diagnosis is usually difficult.CASE SUMMARY We describe a 27-year-old woman who presented with stomatitis,conjunctivitis,and skin blisters and erosions as her first symptoms of PNP with an intraabdominal IPT-like FDC sarcoma.The patient underwent surgical tumor resection and received tapering oral corticosteroid treatment.She showed no recurrence at the 1-year follow-up.CONCLUSION IPT-like FDC sarcomas are rare underlying neoplasms that have an uncommon association with PNP.PNP-associated FDC sarcomas predominantly occur in intra-abdominal sites and suggest a poor prognosis.Surgical resection is an essential and effective treatment for PNP and primary and recurrent FDC sarcomas.

Inflammatory pseudotumor-like follicular dendritic cell sarcoma:Literature review of 67 cases

Inflammatory pseudotumor(IPT)-like follicular dendritic cell(FDC)sarcoma is rare.The 2017 World Health Organization classification of tumors of hematopoietic and lymphoid tissues noted that data on its clinical outcome are limited,but that the tumor appears to be indolent.The aim of this study was to summarize the clinical characteristics,treatment outcomes,and prognostic factors for IPT-like FDC sarcoma.A literature review was conducted on retrospective analyses of clinical data and prognostic information on IPT-like FDC sarcoma reported between 2001 and 2020.A total of 67 cases of IPT-like FDC sarcoma were retrieved from the literature,documenting that it occurs predominantly in middle-aged adults,with a marked female predilection.Six patients had a separate malignancy and five had an autoimmune disease.Typically involving the spleen and/or liver,it may also selectively involve the abdomen,gastrointestinal tract,pancreas,retroperitoneum,and mesentery.Necrosis,hemorrhage,noncaseating epithelioid granulomas,and fibrinoid deposits in blood vessel walls are often present.The neoplastic cells are predominantly positive for follicular dendritic cell markers such as cluster of differentiation 21(CD21),CD23,CD35 and CNA.42 and are consistently Epstein-Barr virus(EBV)-positive.Mitoses were very rare in most cases.Most patients were treated by surgery alone.Disease status at the time of last follow-up was known for 57 patients with follow-up time ranging from 2 to 144 mo.Local and/or distant recurrence after initial treatment was seen in 15.8%of the patients.The 1-and 5-year progression-free survival for the entire group was 91.5%and 56.1%,respectively.Kaplan-Meier and multivariate analyses showed that age,sex,tumor size,and pathological features were not risk factors for disease progression.IPT-like FDC sarcoma appears to be mildly aggressive and requires annual surveillance.Surgery is the most effective treatment modality,and the role of adjuvant chemotherapy for postoperative management is unclear.EBV is likely to play an important role in the etiology of IPT-like FDC sarcoma.

Surgical treatment of liver inflammatory pseudotumor-like follicular dendritic cell sarcoma: A case report

BACKGROUND Inflammatory pseudotumor-like follicular dendritic cell sarcoma(IPT-like FDCS)is rare with a low malignant potential.Hepatic IPT-like FDCS has similar clinical features to hepatocellular carcinoma(HCC),making it extremely difficult to distinguish between them in clinical practice.We describe the case of a young female patient diagnosed with HCC before surgery,which was pathologically diagnosed as IPT-like FDCS after the left half of the liver was resected.During 6 mo of follow-up,the patient recovered well with no signs of recurrence or metastasis.CASE SUMMARY A 23-year-old female patient with a 2-year history of hepatitis B presented to the Affiliated Hospital of Guizhou Medical University.She was asymptomatic at presentation,and the findings from routine laboratory examinations were normal except for slightly elevated alpha-fetoprotein levels.However,ultrasonography revealed a 3-cm diameter mass in the left hepatic lobe,and abdominal contrastenhanced computed tomography revealed that the tumor had asymmetrical enhancement during the arterial phase,which declined during the portal venous phase,and had a pseudo-capsule appearance.Based on the findings from clinical assessments and imaging,the patient was diagnosed with HCC,for which she was hospitalized and had undergone laparoscopic left hepatectomy.However,the tumor specimens submitted for pathological analyses revealed IPT-like FDCS.After surgical removal of the tumor,the patient recovered.In addition,the patient continued to recover well during 6 mo of follow-up.CONCLUSION Hepatic IPT-like FDCS is difficult to distinguish from HCC.Hepatectomy may provide beneficial outcomes in non-metastatic hepatic IPT-like FDCS.

Thyroid follicular renal cell carcinoma excluding thyroid metastases:A case report

BACKGROUND Thyroid follicular renal cell carcinoma is a special type of renal cell carcinoma newly recognized in recent years.It has attracted attention because of its unique histology,immunophenotype,and clinical characteristics.It has a very low incidence,and the number of case reports available for review is limited.Moreover,a thyroid mass with type of tumour is rare.CASE SUMMARY We report a case of a renal mass with a bilateral thyroid mass that was accidentally discovered in a 60-year-old man during physical examination.B-mode ultrasound showed a hypoechoic mass in the middle and lower parenchyma of the right kidney,and computed tomography showed an iso-density shadow tumour in the right kidney.Contrast agents had a significant continuous enhancement effect on the tumour,and the enhancement was not uniform.After partial nephrectomy,pathological analysis was performed to rule out the possibility that the renal tumour was caused by thyroid tumour metastasis.Needle biopsy of the thyroid tumour confirmed that the renal cell carcinoma was not related to the thyroid tumour.The patient was alive at the last postoperative follow-up.CONCLUSION This is the third published case in which thyroid tumour biopsy was performed to confirm that thyroid follicular renal cell carcinoma is not thyroid related.

A T follicular helper cell origin for T regulatory type 1 cells

Chronic antigenic stimulation can trigger the differentiation of antigen-experienced CD4+T cells into T regulatory type 1(TR1)cells,a subset of interleukin-10-producing Treg cells that do not express FOxP3.The identities of the progenitor(s)and transcriptional regulators of this T-cell subset remain unclear.Here,we show that the peptide-major histocompatibility complex class Il(pMHCll)monospecific immunoregulatory T-cell pools that arise in vivo in different genetic backgrounds in response to pMHCll-coated nanoparticles(pMHCll-NPs)are invariably comprised of oligoclonal subpools of T follicular helper(TFH)and TR1 cells with a nearly identical clonotypic composition but different functional properties and transcription factor expression profles.Pseudotime analyses of scRNAseq data and multidimensional mass cytometry revealed progressive downregulation and upregulation of TFH and TR1 markers,respectively.Furthermore,pMHCIl-NPs trigger cognate TR1 cell formation in TFH cell-transfused immunodeficient hosts,and T-cell-specific deletion of Bcl6 or Irf4 blunts both the TFH expansion and TR1 formation induced by pMHCl-NPs.In contrast,deletion of Prdm1 selectively abrogates the TFH-to-TR1 conversion.Bcl6 and Prdm1 are also necessary for anti-CD3 mAbinduced TR1 formation.Thus,TFH cells can differentiate into TR1 cells in vivo,and BLIMP1 is a gatekeeper of this cellular reprogramming event.

The role of the T follicular helper cells in allergic disease

T follicular helper （Tfh） cells were discovered just over a decade ago as germinal centre T cells that help B cells make antibodies. Included in this role is affinity maturation and isotype switching. It is here that their functions become less clear. Tfh cells principally produce IL-21 which inhibits class switching to IgE. Recent studies have questioned whether the germinal centre is the main site of IgE class switching or IgE affinity maturation. In this review, I will examine the evidence that these cells are responsible for regulating IgE class switching and the relationship between Tfh cells and T helper 2 （Th2） effector cells.

IL-10-producing regulatory B cells restrain the T follicular helper cell response in primary Sjögren’s syndrome

Increased numbers of T follicular helper(Tfh)cells have been implicated in the development of autoimmune diseases including primary Sjögren’s syndrome(pSS),but how the Tfh cell response is regulated during autoimmune pathogenesis remains largely unclear.Here,we first found negative correlations between IL-10^(+)regulatory B(Breg)cell numbers and Tfh cell responses and disease activity in patients with pSS and mice with experimental Sjögren’s syndrome(ESS).Moreover,we detected high expression of IL-10 receptor on Tfh cells and their precursors in both humans and mice.In culture,IL-10 suppressed human and murine Tfh cell differentiation by promoting STAT5 phosphorylation.By using an adoptive transfer approach and two-photon live imaging,we found significantly increased numbers of Tfh cells with enhanced T cell homing into B cell follicles in the draining cervical lymph nodes of RAG-2−/−mice transferred with IL-10-deficient B cells during ESS development compared with those of RAG-2−/−mice transferred with wild-type B cells.In ESS mice,CD19^(+)CD1d^(hi)CD5^(+)Breg cells with decreased IL-10 production exhibited severely impaired suppressive effects on T cell proliferation.Consistently,CD19^(+)CD24^(+)CD38^(hi) Breg cells from pSS patients showed significantly reduced IL-10 production with defective inhibitory function in the suppression of autologous Tfh cell expansion.Furthermore,the adoptive transfer of IL-10-producing Breg cells markedly suppressed the Tfh cell response and ameliorated ESS progression in ESS mice.Together,these findings demonstrate a critical role for IL-10-producing Breg cells in restraining the effector Tfh cell response during pSS development.

The development and function of follicular helper T cells in immune responses

Follicular helper T cells （Tfh） have been referred as a lineage that provides a help for B cells to proliferate and undergo antibody affinity maturation in the germinal center. Evidence has supported that Tfh subset development, like other lineages, is dependent on microenvironment where a particular transcriptional program is initiated. It has been shown that Bcl-6 and IL-21 act as master regulators for the development and function of Tfh cells. Tfh dysregulation is involved in the development of autoimmune pathologies, such as systemic lupus erythematosus, rheumatoid arthritis and other autoimmune diseases. The present review highlights the recent advances in the field of Tfh cells and focus on their development and function.

Shared and distinct roles of T peripheral helper and T follicular helper cells in human diseases

The interactions of CD4^(+)T cells and B cells are fundamental for the generation of protective antibody responses,as well as for the development of harmful autoimmune diseases.Recent studies of human tissues and blood samples have established a new subset of CD4^(+)B helper T cells named peripheral helper T(Tph)cells.Unlike T follicular helper(Tfh)cells,which interact with B cells within lymphoid organs,Tph cells provide help to B cells within inflamed tissues.Tph cells share many B helper-associated functions with Tfh cells and induce B cell differentiation toward antibody-producing cells.The differentiation mechanism is also partly shared between Tph and Tfh cells in humans,and both Tfh and Tph cells can be found within the same tissues,including cancer tissues.However,Tph cells display features distinct from those of Tfh cells,such as the expression of chemokine receptors associated with Tph cell localization within inflamed tissues and a low Bd-6/Blimp1 ratio.Unlike that of Tfh cells,current evidence shows that the target of Tph cells is limited to memory B cells.In this review,we first summarize recent findings on human Tph cells and discuss how Tph and Tfh cells play shared and distinct roles in human diseases.

Understanding the development and function of T follicular helper cells

A fundamental function of T helper(Th)cells is to regulate B-cell proliferation and immunoglobulin class switching,especially in the germinal centers.Th1 and Th2 lineages of CD41 T cells have long been considered to play an essential role in helping B cells by promoting the production immunoglobulin G2a(IgG2a)and IgG1/IgE,respectively.Recently,it has become clear that a subset CD41 T cells,named T follicular helper(Tfh)cells,is critical to B-cell response induction.In this review,we summarize the latest advances in our understanding of the regulation of Tfh cell differentiation,the relationship of Tfh cells to other CD41 T-cell lineages,and the role of Tfh cells in health and disease.

Isolated lymphoid follicles in colon: Switch points between inflammation and colorectal cancer?

Gut-associated lymphoid tissue is supposed to play a central role in both the organization of colonic repair mechanisms and colorectal carcinogenesis. In inflammatory conditions, the number, diameter and density of isolated lymphoid follicles (ILFs) increases. They are not only involved in immune surveillance, but their presence is also indispensable in normal mucosal regeneration of the colon. In carcinogenesis, ILFs may play a dual role. On the one hand they may support tumor growth and the metastatic process by vascular endothelial growth factor receptor signaling and producing a specific cytokine and cellular milieu, but on the other hand their presence is sometimes associated with a better prognosis. The relation of ILFs to bone marrow derived stem cells, follicular dendritic cells, subepithelial myofibroblasts or crypt formation, which are all involved in mucosal repair and carcinogenesis, has not been directly studied. Data about the putative organizer role of ILFs is scattered in scientific literature.

New insights into the immunopathogenesis of systemic lupus erythematosus： the role of T follicular helper cells

Objective To review the development of T follicular helper （TFH） cells and their role in systemic lupus erythematosus （SLE） pathogenesis, the effect of dendritic cells （DCs） on TFH cells in SLE, as well as the potential use of TFH cells as a new therapeutic target in clinical practice. Data sources The data used in this review were retrieved mainly from the PubMed database （1989-2013）. The terms used in the literature search were ＂T follicular helper cells,＂ ＂systemic lupus erythematosus,＂ and ＂dendritic cells.＂ Study selection Relevant publications about the TFH cells development, the interaction between the TFH cells and the DCs, and the clinical applications of TFH cells were identified, retrieved, and reviewed. Results TFH cells, a novel distinct CD4＋ T cell subset, are specialized in providing help to B cells in the formation of germinal centers （GCs） and long-term protective humoral immune responses. The development of TFH cells from naive CD4＋ T cell is a multistep process. As the pivot of immunoregulation, DCs are indispensable for TFH cells generation. In addition to receptor-ligand interactions between TFH cells and DCs, the cytokines secreted by DCs are also necessary for TFH cell generation. TFH cell dysregulation has been implicated in the development of SLE. More evidence from animal models of SLE and SLE patients suggests that TFH cells are necessary for pathogenic autoantibody production. Therefore, therapeutically targeting TFH cells can be a promising approach to treat antibody-mediated autoimmune diseases including SLE. Conclusion TFH cells play a critical role in the pathogenesis of SLE, making them attractive therapeutic targets in clinical practice.

Levels of circulating follicular helper T cells,T helper 1 cells,and the prognostic significance of soluble form of CD40 ligand on survival in patients with alcoholic cirrhosis

Background:Excessive drinkers(ED)and patients with alcoholic liver disease(ALD)are several times more susceptible to bacterial and viral infections and have a decrease in antibody responses to vaccinations.Follicular helper T(TFH)cells are essential to select B cells in the germinal center and to produce antibodies.TFH cells express both a membrane-associated and a soluble form of CD40 ligand(sCD40L),in which the latter form is released to circulation upon T cell activation.The effect of alcohol on TFH cells has not been studied.Objectives:The goals of this study are to determine the levels of TFH and T helper 1(Th1)cells in ED and those with alcoholic cirrhosis(AC)when compared to healthy controls and to determine the prognostic significance of sCD40L in a cohort of patients with AC.Methods:Controls,ED,and those with AC were enrolled.Baseline demographic,laboratory tests,and peripheral blood mononuclear cells(PBMCs)were isolated and assessed via flow cytometry for TFH cells.In vitro study was performed to determine the ability of PBMCs to secrete interferon(IFN)-ɣupon stimulation.Serum sCD40L was also determined and its prognostic significance was tested in a cohort of AC patients.Results:The levels of circulating TFH(cTFH)cells were significantly lower in peripheral blood of subjects with ED and AC compared to controls(P<0.05).IFN-ɣsecretion from PBMCs upon stimulation was also lower in ED and those with cirrhosis.Serum sCD40L was significantly lower in ED and AC when compared to that in controls(P<0.0005).Its level was an independent predictor of mortality.Conclusions:Patients with AC had significantly lower level of cTFH and sCD40L.The level of sCD40L was an independent predictor of mortality in these patients.

Advances in the role of follicular T helper cells in graft versus host diseases

Graft versus host disease(GVHD)is a refractory complication of allogeneic hematopoietic stem cell transplantation for the treatment of malignant and non-malignant hematopoietic diseases.Inflammatory cascade responses and cellular immune reactions are the major factors underlying GVHD pathogenesis.Cells producing the cytokine,interleukin(IL)-21 are crucial players involved in injured tissues in GVHD patients.Besides T helper 17 cells,follicular T helper(Tfh)cells are a new source of IL-21 and play a vital role in GVHD pathogenesis.Tfh cell function is mostly regulated by T-follicular regulatory(Tfr)cells that are also located in the germinal center.This review highlights recent advances in the role of Tfh and Tfr cell function in GVHD pathogenesis.New insights are provided into the potential for clinical application in GVHD prevention and treatment.

B cell development and antibody responses in human immune system mice:current status and future perspective

Humanized immune system(HIS)mice have been developed and used as a small surrogate model to study human immune function under normal or disease conditions.Although variations are found between models,most HIS mice show robust human T cell responses.However,there has been unsuccessful in constructing HIS mice that produce high-affinity human antibodies,primarily due to defects in terminal B cell differentiation,antibody affinity maturation,and development of primary follicles and germinal centers.In this review,we elaborate on the current knowledge about and previous attempts to improve human B cell development in HIS mice,and propose a potential strategy for constructing HIS mice with improved humoral immunity by transplantation of human follicular dendritic cells(FDCs)to facilitate the development of secondary follicles.

Two cases of extranodal follicular dendritic cell sarcoma

Follicular dendritic cell (FDC) is an essential component of the nonlymphoid, nonphagocytic immunoaccessory reticulum cells of the peripheral lymphoid tissue(1). FDCs are confined largely to the primary and secondary B-cell follicles, where they form a tight interlacing meshwork. They play a role in the capture and presentation of antigens, generation and regulation of immune complexes. FDCs can be recognized morphologically by their indistinct cellular borders, pale eosinophilic cytoplasm, round-to-ovoid nuclei with delicate nuclear membranes and clear-to-vesicular chromatin with inconspicuous or small nucleoli. FDCs are best identified through immunostaining using CD21, CD35, R4/23, KiM4, KiM4p and Ki-FDC1p. A proliferation of FDCs may be seen in a variety of lesions, including reactive follicular. hyperplasia, Castleman's disease, follicular lymphoma, mantle cell lymphoma, angioimmunoblastic T-cell lymphoma and nodular lymphocyte predominant Hodgkin's lymphoma. Previous studies(2-5) showed that follicular dendritic cell sarcoma (FDCS) affected predominantly the lymph nodes, with occasional extranodal involvement. As the tumor consists mainly ovoid-to-spindle cells, it is not uncommon to misdiagnose the lesion as a wide variety of other spindle cell sarcomas. This study focused on characterizing the histologic features of extranodal FDCS to promote the recognition of this rare entity for both clinicians and pathologists.