Epstein-barr virus (EBV)-positive inflammatory pseudotumor-like follicular dendritic cell sarcoma (IPT-like FDCS) presenting as thrombocytopenia: A case report and literature review.

Background: Follicular dendritic cell sarcoma (FDCS) represents an exceedingly rare malignant neoplasm. Inflammatory pseudotumor-like follicular dendritic cell sarcoma (IPT-like FDCS) is recognized as a variant manifestation of FDCS. The clinical incidence of this particular disease is remarkably low, resulting in the absence of established standardized clinical protocols for its management and treatment. Methods: Presented here is a case of primary Epstein-Barr virus (EBV)-positive splenic IPT-like FDCS, noteworthy for manifesting thrombocytopenia as its initial symptom. Our study analyzed the clinicopathologic characteristics of this case and 29 previously reported cases identified in the literature. Also, we conducted a comprehensive review of pertinent literature. Results: We administered splenectomy to this patient and verified the diagnosis of EBV-positive IPT-like FDCS through immunohistochemical examination. Postoperatively, the patient underwent a one-year follow-up period, demonstrating no signs of recurrence. Analyzing a total of 30 cases revealed that this disease is more prevalent in female patients (F:M = 1.14:1), with a median age of 62 years. Fifteen patients were asymptomatic, and nine patients presented with abdominal discomfort or pain. All patients underwent surgical treatment. Among the cases, histopathological and immunohistochemical information was unavailable for five; however, in the remaining 25 cases, histopathology revealed a distinct inflammatory cell infiltration and spindle tumor cells arranged in sheets or fascicles. These tumor cells had vesicular chromatin and distinct nucleoli and they expressed conventional FDC markers. In situ hybridization analysis of Epstein-Barr virus-encoded small RNA (EBER) showed that all 30 cases were EBV-positive. Follow-up information showed that no patients relapsed and one (3.8 %) patient died. Conclusion: The clinical diagnosis of EBV-positive IPT-like FDCS poses considerable challenges, necessitating a conclusive diagnosis through pathological immunohistochemical examination. EBER in situ hybridization holds significance for the definitive diagnosis of the disease. We advocate for splenectomy as the treatment of choice for limited splenic IPT-like FDCS.

Apatinib manifests an unexpectedly favorable outcome in the management of axillary lymph node follicular dendritic cell sarcoma: a case report.

We present a case of follicular dendritic cell sarcoma in the axillary lymph node, which unexpectedly showed favorable outcomes after the application of apatinib. Follicular Dendritic Cell Sarcoma (FDCS) exhibits a rare incidence and an unclear pathogenic mechanism, contributing to the limited breakthroughs in its treatment to date within the medical field. The current mainstream therapeutic approaches include surgery, CHOP(cyclophosphamide, doxorubicin, vincristine, prednisone), ICE(ifosfamide, carboplatin, etoposide), ABVD(doxorubicin, bleomycin, vinblastine, dacarbazine), and immune checkpoint inhibitors. A 38-year-old male patient was admitted to the hospital due to a lump in the right axilla and underwent surgical treatment. Postoperative pathology confirmed the diagnosis of follicular dendritic cell sarcoma. Two months post-surgery, he faced a recurrence, prompting a subsequent surgical intervention complemented by tumor radiofrequency ablation. Despite these interventions, the treatment response was suboptimal. Subsequently, the patient was treated with the CHOP regimen, but after two cycles, he developed bone metastasis. Due to the patient's limited financial resources and refusal of immunotherapy, we switched to a regimen of gemcitabine and docetaxel, but the disease progressed again after two cycles. A one-cycle trial of albumin-bound paclitaxel yielded unsatisfactory results. Ultimately, the patient was treated with Apatinib, achieving a 10-month progression-free survival. Due to the patient's limited financial circumstances, we, in the absence of guideline recommendations and evidence from evidence-based medicine, achieved a 10-month progression-free survival (PFS) solely based on experiential use of the anti-angiogenic drug, Apatinib. The purpose of this case report is to provide additional therapeutic options for FDCS treatment and to pave the way for exploring the mechanism of action of Apatinib in FDCS.

Case report: Splenic inflammatory pseudotumor-like follicular dendritic cell sarcoma (IPT-like FDCS): a trial of immunotherapy and review of the literature.

Inflammatory pseudotumor-like follicular dendritic cell sarcoma (IPT-like FDCS) is a rare malignancy with fewer than 150 cases in the literature. IPT-like FDCS follows an indolent course with most cases definitively managed with surgical resection. We present a case of IPT-like FDCS with multiple recurrences with a trial of immunotherapy. The patient initially presented with splenic involvement requiring splenectomy, subsequently recurring in the liver requiring hepatic resections. Afterwards, there was recurrence with pelvic/small bowel involvement for which treatment was trialed with ipilimumab and nivolumab. The patient progressed despite dual immune checkpoint inhibitor therapy requiring a small bowel resection. To date, this is the first case of immunotherapy use in IPT-like FDCS. Therefore, more evidence is needed to support additional treatments in recurrent IPT-like FDCS after resection.

Cytological diagnosis of follicular dendritic cell sarcoma with a unique pattern of D2-40 immunoexpression.

Fine needle aspiration procedure is routinely used for cytological diagnosis of nodal or extra nodal lesions. Follicular dendritic cell sarcoma (FDCS) is a rare mesenchymal neoplasm arising from follicular dendritic cells of lymphoid follicles at nodal and extranodal sites. Multimodal therapies have emerged for FDCS, necessitating its accurate pathologic diagnosis with additional ancillary testing for directing clinical management. By immunohistochemical analysis, FDCS is positive for the complement receptors CD21, CD23, and CD35. In addition, D2-40 is reported to be highly sensitive for FDCS with a strong membranous pattern of expression. In this study, we present the cytological diagnosis of a case of FDCS in retroperitoneal lymph nodes with an emphasis on a unique staining pattern of D2-40 which showed a strong nuclear pattern in tumor cells comparable to the membranous pattern of D2-40 on the control tissue and other surgical cases of FDCS in our comparative study.

Follicular Dendritic Cell Sarcoma of the Parotid Gland: A Case Report and Review of Literature.

Follicular dendritic cell sarcoma of the parotid gland is an extremely rare tumor, with only six cases reported in the literature. A 51-year-old female had a 3.0 cm tumor resected from the right parotid gland. The tumor exhibited solid sheets, whorls, fascicular pattern, and syncytium appearance with an indistinct cell border. The lymphocytic infiltrate was sprinkled throughout the neoplasm, with focal prominent perivascular cuffing. Immunohistochemically, it was positive for follicular dendritic cell markers CD21, CD23, and CD35. We aim to enhance the understanding of this neoplasm and alert pathologists to this rare entity in this region to avoid misdiagnosis.

The Transformation of Neck Unicentric Castleman's Disease to Follicular Dendritic Cell Sarcoma.

A patient with a large neck mass underwent appropriate imaging, routine blood tests, and serological evaluations. The medical history revealed the patient had undergone a lymphadenectomy in the same region 8 years ago, and the pathological diagnosis was the hyaline-vascular subtype of unicentric Castleman's disease (UCD). The incisional biopsy and subsequent histopathological and immunohistochemical examination revealed the diagnosis of follicular dendritic cell sarcoma, consistent with the malignant transformation of UCD. UCD is uncommon and the malignant transformation of UCD is extremely rare in the head and neck region. Regional lymph node resection of one or more adjacent regions is the preferred treatment choice. Appropriate treatment procedures for UCD and regular follow-up are essential for a good prognosis. Laryngoscope, 2024.

EBV-positive inflammatory follicular dendritic cell sarcoma of the colon with clonal immunoglobulin gene rearrangement: A case report and literature review.

Introduction: Epstein-Barr virus-positive (EBV+) inflammatory follicular dendritic cell (FDC) sarcoma is a rare neoplasm characterized by spindle-shaped follicular dendritic cells, marked lymphoplasmacytic infiltration, and a consistent link to EBV. While it typically affects the liver and spleen, it is exceptionally rare in the digestive tract. We present a special case of EBV + inflammatory FDC sarcoma arising in the colon with clonal immunoglobulin (IG) gene rearrangement. Case presentation: A 70-year-old man presented with a one-month history of abdominal distension. Colonoscopy revealed a pedunculated polyp in the ascending colon, which was subsequently removed via endoscopic polypectomy. Histological examination of the colonic polyp demonstrated a pronounced lymphoplasmacytic infiltrate with scattered EBV + neoplastic cells, as evidenced by EBV-encoded small RNA in situ hybridization (EBER ISH). The neoplastic cells were positive for FDC-specific markers, including CD21, CD35, and CD23. Additionally, the tumor exhibited clonal rearrangement of the immunoglobulin heavy chain (IGH) gene. The diagnosis was confirmed as EBV + inflammatory follicular dendritic cell sarcoma. Conclusions: We described an exceptional case of EBV + inflammatory FDC sarcoma presenting as a colonic polyp, featuring a clonal IGH gene rearrangement not previously documented in this colonic tumor type. Heightened awareness of this rare neoplasm within the gastrointestinal tract is essential for both accurate diagnosis and effective patient management.

Imaging findings of Epstein-Barr Virus-positive inflammatory follicular dendritic cell sarcoma of spleen: A case report.

BACKGROUND: Spleen Epstein-Barr Virus (EBV)-positive inflammatory follicular dendritic cell sarcoma (FDCS) is rare, and the imaging signs are unclear. The COVID-19 has been confirmed to be the cause of pneumonia and can cause a variety of diseases including myocarditis. However, it has not been reported to be the cause of the exacerbation or activation of EBV-positive inflammatory FDCS. OBJECTIVE: The objective is to extract the imaging features of EBV-positive inflammatory FDCS in the spleen and analyze the reasons for the special features of this case. METHODS: By analyzing the patient's treatment process and imaging examinations (A 77-year-old female was admitted to the hospital due to generalized discomfort and pain symptoms. When she was admitted to the hospital a year earlier with COVID-19 pneumonia, a chest CT scan showed that she had a splenic tumor. During this admission, CT scans showed two irregularly shaped and unevenly dense soft tissue density masses within the spleen, with uneven enhancement on contrast-enhanced im-aging within the solid components and along the edges. PET/CT scans revealed elevated glucose metabolism in the masses. Postoperative pathological diagnosis confirmed splenic EBV-positive inflammatory FDCS.), reading the literature, sorting out the disease cognitive process, epidemiology, and pathological data of EBV-positive inflammatory FDCS, we discussed the imaging manifestations and possible differential diagnosis of the disease. RESULTS: The patient was finally diagnosed with splenic EBV-positive inflammatory FDCS. CONCLUSIONS: Imaging features of EBV-positive inflammatory FDCS in the spleen include a high incidence of hemorrhage and necrosis, persistent moderate enhancement of the solid portion, a "capsular-like enhancement" structure at the tumor edge, and possibly active glucose metabolism with high Standardized Uptake Values (SUVs). COVID-19 infection and long-term COVID-19 sequelae may exacerbate and activate EBV-positive inflammatory FDCS in the spleen, and the mechanism remains to be further studied.

Clinicopathological Analysis of Epstein-Barr Virus-Positive Inflammatory Follicular Dendritic Cell Sarcoma of the Spleen: A Case Report.

OBJECTIVE: The present study aims to explore the clinicopathological characteristics of Epstein-Barr virus (EBV)-positive inflammatory follicular dendritic cell sarcoma (IFDCS; EBV+ IFDCS). CASE REPORT: The case involved a 32-year-old woman who underwent surgical resection of a splenic nodule. Histological examination and immunohistochemistry were performed using cluster of differentiation (CD) markers, and in-situ hybridization was conducted to detect EBV-encoded RNA (EBER). RESULTS: A microscopic analysis revealed neoplastic cells with various morphologies, including round, ovoid, or spindled shapes, dispersed within a prominent lymphoplasmacytic infiltrate. The tumor cells exhibited nuclear atypia, with some resembling Reed-Sternberg cells. The immunohistochemistry demonstrated focal positivity for follicular dendritic cell markers, such as CD21, CD23 and CD35, and focal negativity for other markers, including CD3, CD34, CD20, CD79a, myeloperoxidase and HMB45. Additionally, the EBER staining showed strongly positive results. The patient showed no local recurrence or metastasis during the 13-month follow-up. CONCLUSION: A comprehensive understanding of EBV+IFDCS, including its clinicopathological features and immunohistochemical characteristics, is crucial for accurate diagnosis and differential diagnosis of this rare tumor.

Long-Term Follow-Up of Combination Therapy with Sintilimab and Anlotinib in Gallbladder Follicular Dendritic Cell Sarcoma: A Rare Case Report.

Follicular dendritic cell sarcoma (FDCS) is a rare malignant neoplasm for which a standardized treatment approach has yet to be established. The prevailing therapeutic strategy typically involves resection followed by adjuvant chemotherapy or radiation. This case report details the long-term follow-up of a 59-year-old Chinese male diagnosed with gallbladder FDCS and liver metastases. The patient received a combination therapy of sintilimab and anlotinib, resulting in a substantial partial response (PR) lasting for a noteworthy duration of 30 months. Notably, this is the first documented instance of gallbladder FDCS with liver metastases being treated with PD-1 antibody and antiangiogenic agents as first-line therapy. These findings suggest that this treatment regimen may offer a potential therapeutic option for patients with gallbladder FDCS and liver metastases, with a duration of PR lasting up to 30 months.

Rare co-occurrence of tonsillar follicular dendritic cell sarcoma and schizophrenia: A comprehensive study.

This study investigated the infrequent occurrence of tonsillar follicular dendritic cell sarcoma (FDCS) co-existing with schizophrenia, presenting a comprehensive examination of clinical, pathological, and literature aspects. A systematic literature review was conducted, focusing on articles related to "schizophrenia" and "sarcoma," with in-depth analysis of included case reports. Clinical data, pathological findings, and patient follow-up information were collected and synthesized. The study detailed a rare case of FDCS in the tonsil concurrent with schizophrenia, providing insights into diagnosis, treatment, and follow-up. A literature review of combined FDCS in the tonsil and schizophrenia cases highlighted their clinical and pathological characteristics. Eight case reports encompassing 11 patients diagnosed with sarcoma and schizophrenia were included. Surgical resection was the preferred primary treatment, while chemotherapy was suggested for recurrences. Instances of co-occurring FDCS and schizophrenia were exceptionally limited, with tonsillar FDCS being particularly uncommon. The coexistence of tonsillar FDCS and schizophrenia was an exceptionally rare condition, posing diagnostic and therapeutic challenges. This study contributed valuable insights into clinical and pathological practice through a systematic review, underscoring the significance of early diagnosis and comprehensive management.

Follicular dendritic cell sarcoma arising from the lymph node of the pancreatic head: a case report with literature review.

A 72-year-old man was referred to our hospital for the examination of a pancreatic head mass. Abdominal computed tomography revealed a contrasted 8-cm-diameter tumor extending from the dorsal pancreatic head to the porta hepatis. The preoperative diagnosis was challenging due to the absence of specific imaging findings and the inability to perform a biopsy. Positron emission tomography/computed tomography and diffusion-weighted imaging suggested a malignant tumor originating from the organs surrounding the pancreatic head. Subtotal stomach-preserving pancreaticoduodenectomy with regional lymph node dissection was performed, as dissection from the pancreatic head proved unfeasible. Pathological examination identified the tumor as an enlarged lymph node consisting of pleomorphic large cells forming clusters, positive for follicular dendritic cell markers cluster of differentiation (CD) 21 and CD23. No evidence of tumor capsule infiltration, other organ infiltration, or metastasis to other lymph nodes was observed. The final diagnosis was nodal follicular dendritic cell sarcoma (FDCS) originating from the pancreatic head lymph nodes. No recurrence occurred at 3 years postoperatively with no postoperative treatment. Intraperitoneal nodal FDCS is extremely rare, and occasionally, it can lead to postoperative recurrence and progression. It is crucial to differentiate neoplastic lymph node enlargement around the pancreatic head from nodal FDCS.

Extranodal follicular dendritic cell sarcoma of the lung.

Follicular dendritic cell sarcoma (FDCS) is a rare, mesenchymal neoplasm that may be nodal or extranodal in location. Lung involvement is rare. It is a slow-growing, painless tumor with a frequent capacity to recur and metastasize. We present a case of extranodal FDCS of the lung with an unusual presentation. A 34-year-old man presented with the complaints of haemoptysis and chest pain. A large left perihilar mass with endobronchial component was found on radiological evaluation. On endobronchial biopsy and mediastinal tru-cut biopsy, differential diagnoses of an inflammatory myo-fibrohistiocytic lesion and leiomyosarcoma were provided on the basis of morphological features of bipolar spindled cells arranged in intersecting fascicles and storiform patterns and immunophenotyping. A pneumonectomy was performed for the mass on which further immunohistochemical evaluation with CD21, CD35, and D2-40 finally helped form a diagnosis of FDCS. The patient recovered well from the surgery and has been on follow-up ever since. Owing to the rarity of this condition and its non-specific clinical features, FDCS is often misdiagnosed in the absence of appropriate immunohistochemistry. An of awareness of its morphological features and immunophenotype is, thus, necessary to provide early treatment and follow-up in order to prevent its recurrence and metastasis.

Clinicopathologic profile of intra-abdominal follicular dendritic cell sarcoma: A study of three cases with a literature review.

Follicular dendritic cell sarcoma (FDCS) is a rare tumor, which mainly originates from follicular dendritic cells (FDCs) in the lymph nodes. Sometimes FDCS can arise from outside the lymph nodes. FDCS is an extremely rare malignant tumor in intraperitoneal or retroperitoneal tissue. We gathered the detailed clinical data of three patients diagnosed with FDCS in the abdomen. The clinical observations and histopathologic and immunohistochemical features of FDCS were analyzed. The patients included two men and one woman aged 55 ~ 61 years old. The mesentery of the small intestine and colon was involved in case 1, spleen in case 2, and retroperitoneal tissues in case 3. Two patients presented with abdominal masses, and one presented with no obvious symptoms. Histology showed ovoid to spindle neoplastic cells arranged in fascicles and storiforms with inflammatory infiltrate as well as whorled patterns in some areas. Immunohistochemical staining was positive for CD21, CD23, CD35, and SSTR2. FDCS exhibits no characteristic clinical manifestations. Morphologically, FDCS can have overlapping features with many other entities, leading to misdiagnosis. The use of histopathology supplemented with FDC markers, such as CD21, CD23, and CD35, is useful for diagnosis and differential diagnosis.

Epstein-Barr virus-positive inflammatory follicular dendritic cell sarcoma with significant granuloma: case report and literature review.

BACKGROUND: Epstein-Barr virus-positive inflammatory follicular dendritic cell sarcoma (EBV+IFDCS) is a rare disease characterized by mild clinical symptoms and non-specific imaging findings. The diagnosis of the disease depends on pathological diagnosis. However, EBV+IFDCS has a very broad spectrum of histological morphology and immune phenotypes, and its histopathological features have not been fully described by pathologists. CASE PRESENTATION: A 59-year-old female, with no significant discomfort, was found to have a splenic mass during a routine physical examination. Microscopic examination at low magnification revealed numerous epithelioid granulomas, amidst which a substantial inflammatory response was observed. Interspersed among the dense inflammatory cells were spindle or oval-shaped cells, distributed sporadically with indistinct boundaries. Under high magnification, these spindle cells had subtle features: smooth and clear nuclear membranes, inconspicuous small nucleoli, and infrequent mitotic figures. Immunophenotypically, the spindle cells expressed CD21 and CD23, and Epstein-Barr encoding region (EBER) in situ hybridization yielded positive results. The inflammatory milieu predominantly consisted of T cells, with a minority of plasma cells expressing IgG4. The confluence of morphological and immunohistochemical findings led to the final pathological diagnosis of EBV+IFDCS in this case. CONCLUSIONS: The presentation of EBV+IFDCS with pronounced granulomatous changes is rare. This morphological variant poses a high risk of misdiagnosis, frequently leading to confusion with other granulomatous diseases. Accurate diagnosis necessitates a comprehensive analysis, integrating immunohistochemistry and in situ hybridization. The case presented here is instrumental in raising awareness and understanding of EBV+IFDCS, with the goal of reducing misdiagnoses and unrecognized cases.

Primary follicular dendritic cell sarcoma of the kidney - a case report of a rare tumor with emphasis on diagnostic pitfalls.

BACKGROUND: Follicular dendritic cell sarcoma (FDCS) is a rare low-grade tumor of the lymph nodes, but roughly one-third of the cases emerge from extranodal sites, posing diagnostic challenges. CASE PRESENTATION: In this report, we present the case of a 59-year-old lady who complained of renal colic. During investigation, a kidney tumor was discovered. A radical nephrectomy was performed, and histological examination identified the tumor as a sarcomatoid renal cell carcinoma. The case was then referred to a genitourinary pathologist for further evaluation. The tumor cells exhibited positive staining for CD21, CD23, somatostatin receptor 2 A, and MDM2 expression. Additionally, MDM2 gene amplification was confirmed by the FISH study. Ultimately, the tumor was diagnosed as a primary renal FDCS. The patient was placed under active oncological surveillance and did not receive any further therapy. Remarkably, after 91 months of follow-up, she remains tumor-free. CONCLUSION: This case represents a well-documented primary renal FDCS. Our aim in presenting this extremely rare tumor is to enhance awareness and highlight the importance of considering FDCS in the differential diagnosis.

Case Report: Identification of a novel STAT3 mutation in EBV-positive inflammatory follicular dendritic cell sarcoma.

EBV-positive inflammatory follicular dendritic cell sarcoma (EBV+ IFDCS) is an uncommon disease primarily observed in Asia. It is characterized by the development of tumors believed to originate from follicular dendritic cells (FDC). The consistent association between this condition and clonal EBV infection suggests EBV's involvement as an etiological factor. However, diagnosing EBV+ IFDCS can be challenging due to its morphological variability and diverse immunohistochemical staining patterns. The genetic characteristics of EBV+ IFDCS remain insufficiently understood. To address this knowledge gap, we present a case study of a 47-year-old male patient diagnosed with EBV+ IFDCS. We utilized a Next-generation sequencing (NGS) platform to investigate the genetic profile of the tumor cells. We identified a single pathogenic mutation (G618R) in the STAT3 gene. This finding provides valuable insights into the genetic alterations associated with EBV+ IFDCS and potentially contributes to our understanding of the disease's pathogenesis.

Survival analysis in patients with follicular dendritic cell sarcoma: a population-based study.

Follicular dendritic cell sarcoma (FDCS) is a rare low-intermediate grade malignant neoplasm. To date, published data on FDCS clinical courses are sparse, and no conditional survival study has been performed. Thus, we retrospectively analyzed 187 patients diagnosed with FDCS from the Surveillance, Epidemiology, and End Results (SEER) database. In this study, the median age at diagnosis was 50 years and 91 (48.7%) patients were male. The most common primary location was the abdomen/pelvis (82, 43.9%). The 1-year, 3-year, and 5-year overall survival (OS) were 88.7%, 69.0%, and 59.8%, respectively. The 5-year conditional overall survival increased from 65.7% at baseline to 83.8% in 5-year survivors. The 3-year FDCS-specific death rate was 26.7% and the rate of death from other reasons was 3.7%. In addition, the annual death hazard was the highest in the first four years after diagnosis and increased again in the 7th and 8th years. Age > 60 years at diagnosis, metastatic disease, and FDCS in thoracic organs were associated with shorter OS and FDCS-specific survival. In addition, FDCS patients, with either local or metastatic disease, could benefit from surgery therapy. In addition, adjuvant radiotherapy or chemotherapy for local disease provided no significant improvement in overall survival or FDCS-specific survival. We hope these findings may guide treatments and surveillance strategies for FDCS patients in clinical practice.

Aggressive Variant of Hepatic Epstein-Barr Virus-Associated Inflammatory Pseudotumor-like Follicular Dendritic Cell Sarcoma with PD-L1 and SSTR2a Expression.

An aggressive Epstein-Barr virus (EBV)-associated inflammatory pseudotumor-like follicular dendritic cell (IPT-like FDC) sarcoma is reported in an adult female. The patient developed multifocal recurrence and passed away 13 months after the initial surgical resection. A bright field microscopic examination of the tumor demonstrated a classical growth pattern and the diffuse expression of Programmed death ligand 1 (PD-L1) and somatostatin receptor 2a (SSTR2a).

Favorable response to PD-1 inhibitor plus chemotherapy as first-line treatment for metastatic follicular dendritic cell sarcoma of the spleen: a case report.

Follicular dendritic cell sarcoma (FDCS) is an uncommon low-grade malignant sarcoma. For localized FDCS, surgery is the most commonly recommended therapy option. However, there is no standard treatment protocol for metastatic FDCS. Here, we present a 68-year-old female with primary spleen FDCS who had multiple peritoneal metastases. She was treated with sintilimab (PD-1 inhibitor) plus chemotherapy (epirubicin plus ifosfamide) as first-line treatment achieving partial response (PR) and a relatively long progression-free survival (PFS) of 17 months. This case suggests that PD-1 inhibitor plus chemotherapy as first-line therapy seem to be a promising treatment option for metastatic FDCS.