Application of PD‑L1 blockade in refractory histiocytic sarcoma: A case report

Langerhans Cell Histiocytosis and Other Histiocytic Lesions

BACKGROUND

Histiocytoses, including Langerhans cell histiocytosis (LCH), comprise a diverse group of histiocytic disorders characterized by the abnormal accumulation and proliferation of histiocytes in various tissues or organs throughout the body, ranging from benign, self-limited conditions to aggressive malignancies and systemic inflammatory syndromes. These lesions present unique diagnostic challenges due to their broad spectrum of clinical presentations, overlapping histopathological and immunophenotypical features, and genetic complexity.

METHODS

This review analyzes major histiocytic lesions, focusing on their epidemiology, clinical presentations, histologic and immunophenotypic features, and genetic characteristics to facilitate accurate diagnosis and differentiation among these histiocytoses.

RESULTS

LCH, a well-recognized lesion, can affect various organ systems and necessitates differentiation from other types of histiocytoses such as Erdheim-Chester disease (ECD), Rosai-Dorfman-Destombes disease (RDD), and cutaneous and mucocutaneous non-Langerhans cell histiocytoses. Some histiocytic lesions, such as histiocytic sarcoma, are inherently malignant, while others, like hemophagocytic lymphohistiocytosis (HLH), manifest as severe, potentially life-threatening systemic inflammatory syndromes. Recent molecular genetic studies revealed recurrent genetic alterations in the MAPK pathway, such as BRAF V600E and MAP2K1 in LCH and ECD, and KRAS, NRAS, and MAP2K1 mutations in a subset of RDD. Malignant histiocytoses frequently show alterations in tumor suppressor genes like TP53 and CDKN2A.

CONCLUSION

Precise classification of histiocytic lesions relies on a comprehensive diagnostic approach that integrates clinical, histologic, immunophenotypic, and genetic data. Recent genetic advances shed light on these conditions' unique but occasionally overlapping pathogenic mechanisms. Molecular genetics advancements continue to refine diagnostic accuracy and present new therapeutic targets, especially for aggressive or treatment-resistant cases.

BRAF V600E mutation and high expression of PD-L1 in Rosai-Dorfman disease: case report and review of the literature

BRAF V600E mutations are frequently found in histiocytic/dendritic cell neoplasms such as Erdheim-Chester disease (ECD) and Langerhans cell histiocytosis (LCH), but few reports have also described BRAF mutations in Rosai-Dorfman disease (RDD), and even these cases may predominantly represent mixed histiocytosis. BRAF mutations have been studied in histiocytic/dendritic cell neoplasms and described to be associated with increased risk of relapse and long-term consequences, but few studies have examined BRAF V600E mutation in RDD, which is recognized as a neoplasm given the high frequency of MAPK pathway alterations. Here, we report a case of BRAF V600E-mutated RDD in a patient who presented with generalized lymphadenopathy. During our evaluation of this patient, we also found expression of PD-L1 in neoplastic histiocytes. During our review period, only few cases of RDD reported to harbor BRAF mutation or were evaluated for the expression of PDL1 by neoplastic cells. Given the potential challenges in distinguishing RDD from other histiocytic/dendritic cell neoplasms, including mixed histiocytosis with similar clinicopathological manifestations, we will discuss the current state of knowledge regarding the frequency and clinical impact of BRAF V600E in RDD, as well as the role of BRAF mutations in RDD pathogenesis. Distinction of BRAF V600E mutated histiocytic/dendritic cell neoplasms requires consideration of distinctive histopathological and immunophenotypic findings in appropriate clinical and radiologic setting. Given the increasing use of BRAF inhibitors as well as checkpoint blockade inhibitors to treat a number of cancers, we will discuss the clinical implications of the presence of BRAF V600E mutation and PD-L1 expression in RDD.

Long-Term Remission with Novel Combined Immune-Targeted Treatment for Histiocytic Sarcoma Accompanied by Follicular Lymphoma: Case Report and Literature Review

Histiocytic sarcoma (HS) is an extremely rare but aggressive hematopoietic malignancy, and the prognosis has been reported to be rather unfavorable with a median overall survival of merely 6 months. We presented a 58-year-old female patient complaining of abdominal pain and fever, who was admitted to our institution in September 2021. Fluorine-18-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET/CT) scan showed enlargement of generalized multiple lymph nodes. Subsequently, laparoscopic retroperitoneal lesion biopsy and bone marrow aspiration were performed. The pathological findings indicated the diagnosis of HS concurrent with follicular lymphoma. The immunohistochemistry (IHC) staining of the tumor lesion revealed a high expression of CD38 and PD-L1 proteins. Furthermore, KRAS gene mutation was identified by means of next-generation sequencing. The patient exhibited poor treatment response to both first- and second-line cytotoxic chemotherapies. Therefore, she underwent six cycles of Daratumumab (anti-CD38 monoclonal antibody), Pazopanib (multi-target receptor tyrosine kinases inhibitor) combined with third-line chemotherapy, followed by involved-site radiotherapy and maintenance therapy with the PD-1 inhibitor Tislelizumab. Long-term partial remission was finally achieved after multi-modality treatment. Duration of remission and overall survival reached 22 and 32 months, respectively. Our case indicated that immuno-targeted treatment coupled with chemotherapy and radiotherapy might constitute a potential therapeutic option for HS.

One Health: Therapies Targeting Genetic Variants in Human and Canine Histiocytic and Dendritic Cell Sarcomas

The precise cause of HS/DCS is still unknown. The relatively low incidence in humans urges for an animal model with a high incidence to accelerate knowledge about genetics and optimal treatment of HS/DCS. Namely, until now, the therapies targeting genetic variants are still more experimental and sparsely used, while consensus is missing. In addition, the literature about variants and possible mutation-targeted therapies in humans and dogs consists mainly of case reports scattered throughout the literature. Therefore, an overview is provided of all currently known genetic variants in humans and dogs with HS/DCS and its subtypes, their possible mutation-targeted therapies, their efficacy, and a contemplation about the future. Several genetic variants have already been discovered in HS/DCS, of which many are shared between canine and human HS/DCS, but unique variants exist as well. Unfortunately, none of these already found variants seem to be specifically causal for HS/DCS, and the puzzle of its landscape of genetic variation is far from complete. The use of mutation-targeted therapies, including MAPK-/MEK-inhibitors and the future use of PTPN11-, CDK4/6- and PD-1-inhibitors, seems to be promising for these specific variants, but clearly, clinical trials are needed to determine optimal inhibitors and standardised protocols for all variants. It can be concluded that molecular analysis for variants and subsequent mutation-targeted therapy are an essential addition to cancer diagnostics and therapy. A joint effort of humans and dogs in research is urgently needed and will undoubtedly increase knowledge and survival of this devastating disease in dogs and humans.

Primary pulmonary histiocytic sarcoma with high PD-L1 expression benefited from immunotherapy: A case report and bioinformatic analysis

Histiocytic sarcoma is an aggressive haematopoietic malignancy accounting for less than 1% of haematolymphoid neoplasms with a diagnosis based on morphology and immunophenotype of tissue biopsies with a very poor prognosis. Here, we report a 45-year-old man who was diagnosed with primary pulmonary histiocytic sarcoma with systemic metastases, with partial remission (PR) treated with cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP) chemotherapy, but it relapsed soon after therapy above. Tests demonstrated that TMB was 21 Muts/Mb PD-L1 expression was 90% positive, and the disease has been well-controlled over 3 years using immune checkpoint inhibitors (nivolumab and pembrolizumab). Bioinformatic pan-cancer analysis verified that there was the highest genetic alteration frequency of PD-L1 in which amplification accounted for the majority of sarcoma tumour samples. Following that, we found that the genetic alteration of PD-L1 was associated with poor prognosis in sarcoma patients in terms of overall survival (OS) (p = 1.51 × 10-4 ), progress-free survival (PFS) (p = 4.90 × 10-2 ) and disease-specific survival (DSS) (p = 4.90 × 10-2 ). To our knowledge, this may be the first reported case with high PD-L1 expression in primary pulmonary histiocytic sarcoma who may benefit from immunotherapy such as nivolumab and pembrolizumab significantly and safely.

Pembrolizumab Combined With GDP Regimen Inducing Sustained Remission in Histiocytic Sarcoma: A Case Report

Histiocytic sarcoma (HS) is a rare hematopoietic neoplasm with an aggressive clinical course and a poor response to conventional chemotherapy. Currently, no standard treatment paradigms are available. Herein, we present a case of de novo HS treated with pembrolizumab combined with a GDP regimen (gemcitabine, cisplatin, and dexamethasone) that resulted in sustained complete remission with progression-free survival exceeding 4 years. Immunohistochemical analysis demonstrated significant overexpression of programmed death ligand 1 (PD-L1) on biopsy samples. Additionally, fluorescence in situ hybridization (FISH) with a JAK-2 probe indicated 9p24.1 amplification, suggesting reliance on the JAK-STAT pathway. Polymerase chain reaction (PCR) analysis did not reveal any BRAF-V600 mutations. Consequently, an immune checkpoint inhibitor (ICI) was administered alongside chemotherapy, resulting in sustained complete remission and progression-free survival for over 4 years. Our findings suggest that a combination of ICI and chemotherapy could represent a promising therapeutic approach for HS.

Favorable outcome of a histiocytic sarcoma patient treated with immune checkpoint inhibitor: a case report

Introduction and Importance

Histiocytic sarcoma (HS) is an extremely rare malignancy in which there has been no standard treatment approach. Some preclinical studies have provided rationales for the application of immunotherapy in advanced HS.

Case Presentation

The authors reported a case of a 61-year-old patient with metastatic HS who had a rapid progression on ifosfamide, carboplatin, and etoposide chemotherapy. The authors performed PD-L1 testing, which showed a strong positivity in 90% of tumor cells. The patient was then treated with pembrolizumab 200 mg every 3 weeks. He refused palliative radiotherapy. A dramatic response in all sites was recorded on the PET-CT scan after three cycles. He was maintained on pembrolizumab, reaching over 30 months without disease progression.

Clinical Discussion

Recent molecular data suggests there could be a role of immunotherapy in HS. In our patient, the disease was refractory to chemotherapy and pembrolizumab has been given based on the strong PD-L1 expression. Response to immunotherapy has also been recorded in several cases with malignant histiocytic neoplasm.

Conclusion

Immunotherapy might bring sustained disease remission in PD-L1 high expression HS and further studies evaluating the role of immune checkpoint inhibitor in this disease are warranted.

Histiocytic Sarcoma Treated with Pembrolizumab: A Case Report and Literature Review

Histiocytic sarcoma (HS) is a rare hematologic malignancy that has historically been treated with lymphoma-based regimens with a median survival of 6 months. We describe a case of a 51-year-old woman who presented with acute back pain and cord compression. She was diagnosed with HS with diffuse skeletal lesions and high expression of programmed death ligand 1 (PD-L1). She was subsequently treated with chemotherapy plus off-label use of pembrolizumab followed by allogeneic stem cell transplantation. Ultimately, the patient died in the setting of progression of disease 17 months after her stem cell transplantation and 26 months after her diagnosis. This article also presents a literature review of cases of HS treated with programmed death ligand inhibition.