Primary histiocytic sarcoma presenting as diffuse leptomeningeal disease: Case description and review of the literature

A rare case of primary central nervous system histiocytic sarcoma harboring a novel ARHGAP45::BRAF fusion: a case report and literature review

INTRODUCTION

Patients with histiocytic sarcoma occurring in the central nervous system (CNS) are rare and have a very poor prognosis. The increased use of molecular diagnostic approaches in solid tumors has brought more opportunities for the diagnosis and treatment of central nervous system histiocytic sarcoma (CNSHS).

CASE DESCRIPTION

A 9-year-old girl was admitted to the hospital with pain in her head and neck, as well as vomiting. Imaging scans showed a prominent abnormality in the anterior falciform region, and histopathology revealed the presence of CD68 (+) and CD163 (+) cells, leading to a preliminary diagnosis of primary intracerebral CNSHS. Molecular profiling tests identified a new variant of ARHGAP45::BRAF fusion in this case, which has not been reported in any other tumor. The patient underwent surgical removal of the tumor and will require long-term monitoring.

CONCLUSION

The presence of the BRAF point mutation, predominantly BRAF p.V600E, has been documented in prior literature of CNSHS. This is the first case of pediatric histiocytic sarcoma in the anterior falciform region who has a unique ARHGAP45::BRAF fusion. The findings of our study indicate that a broader range of molecular assays should be employed in the diagnosis of CNSHS and opens up new possibilities for the treatment of the patient.

Primary intracranial histiocytic sarcomas: a report of six cases and a pooled analysis of individual patient data

OBJECTIVE

Primary intracranial histiocytic sarcomas (PIHSs) are extremely rare with limited reported cases, making their prognostic factors and management uncertain. This study aims to describe the clinical characteristics of PIHSs and propose a treatment protocol for this entity.

METHODS

Clinical data were collected from six patients diagnosed with PIHSs at Beijing Tiantan Hospital between March 2011 and October 2022. Additionally, a comprehensive search of the PubMed database was conducted using the keywords "primary intracranial" or "primary central nervous system" combined with "histiocytic sarcoma" or "histiocytic sarcomas" between 1996 and 2022, identifying 24 cases. A pooled analysis of individual patient data was performed to assess risk factors for overall survival (OS).

RESULTS

The six cases included four males and two females, with a mean age of 42.2 ± 13.3 years. In total, 24 cases of PIHSs were identified from previous studies. Multivariate Cox regression analysis revealed that gross total resection (GTR) was the only factor predicting a longer OS (p = 0.027). Kaplan-Meier analysis demonstrated that GTR (p = 0.0013), solitary lesions (p = 0.0048), and radiotherapy (p = 0.0492) were associated with a longer OS.

CONCLUSION

PIHSs are rare brain tumors with poor clinical prognosis. Patients with solitary lesions have a longer OS than those with multifocal lesions. Gross total resection must be the first choice. Radiotherapy may bring benefits for these patients, but chemotherapy may not be useful. Further studies involving larger cohorts are necessary to validate these findings.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 5: Epigenetic Regulation of PD-L1

Epigenetic alterations (including DNA methylation or miRNAs) influence oncogene/oncosuppressor gene expression without changing the DNA sequence. Prostate cancer (PC) displays a complex genetic and epigenetic regulation of cell-growth pathways and tumor progression. We performed a systematic literature review (following PRISMA guidelines) focused on the epigenetic regulation of PD-L1 expression in PC. In PC cell lines, CpG island methylation of the CD274 promoter negatively regulated PD-L1 expression. Histone modifiers also influence the PD-L1 transcription rate: the deletion or silencing of the histone modifiers MLL3/MML1 can positively regulate PD-L1 expression. Epigenetic drugs (EDs) may be promising in reprogramming tumor cells, reversing epigenetic modifications, and cancer immune evasion. EDs promoting a chromatin-inactive transcriptional state (such as bromodomain or p300/CBP inhibitors) downregulated PD-L1, while EDs favoring a chromatin-active state (i.e., histone deacetylase inhibitors) increased PD-L1 expression. miRNAs can regulate PD-L1 at a post-transcriptional level. miR-195/miR-16 were negatively associated with PD-L1 expression and positively correlated to longer biochemical recurrence-free survival; they also enhanced the radiotherapy efficacy in PC cell lines. miR-197 and miR-200a-c positively correlated to PD-L1 mRNA levels and inversely correlated to the methylation of PD-L1 promoter in a large series. miR-570, miR-34a and miR-513 may also be involved in epigenetic regulation.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 3: PD-L1, Intracellular Signaling Pathways and Tumor Microenvironment

The tumor microenvironment (TME) includes immune (T, B, NK, dendritic), stromal, mesenchymal, endothelial, adipocytic cells, extracellular matrix, and cytokines/chemokines/soluble factors regulating various intracellular signaling pathways (ISP) in tumor cells. TME influences the survival/progression of prostate cancer (PC), enabling tumor cell immune-evasion also through the activation of the PD-1/PD-L1 axis. We have performed a systematic literature review according to the PRISMA guidelines, to investigate how the PD-1/PD-L1 pathway is influenced by TME and ISPs. Tumor immune-escape mechanisms include suppression/exhaustion of tumor infiltrating cytotoxic T lymphocytes, inhibition of tumor suppressive NK cells, increase in immune-suppressive immune cells (regulatory T, M2 macrophagic, myeloid-derived suppressor, dendritic, stromal, and adipocytic cells). IFN-γ (the most investigated factor), TGF-β, TNF-α, IL-6, IL-17, IL-15, IL-27, complement factor C5a, and other soluble molecules secreted by TME components (and sometimes increased in patients' serum), as well as and hypoxia, influenced the regulation of PD-L1. Experimental studies using human and mouse PC cell lines (derived from either androgen-sensitive or androgen-resistant tumors) revealed that the intracellular ERK/MEK, Akt-mTOR, NF-kB, WNT and JAK/STAT pathways were involved in PD-L1 upregulation in PC. Blocking the PD-1/PD-L1 signaling by using immunotherapy drugs can prevent tumor immune-escape, increasing the anti-tumor activity of immune cells.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 1: Focus on Immunohistochemical Results with Discussion of Pre-Analytical and Interpretation Variables

Immunotherapy targeting the PD-1-PD-L1 axis yielded good results in treating different immunologically ''hot'' tumors. A phase II study revealed good therapeutic activity of pembrolizumab in selected prostatic carcinoma (PC)-patients. We performed a systematic literature review (PRISMA guidelines), which analyzes the immunohistochemical expression of PD-L1 in human PC samples and highlights the pre-analytical and interpretation variables. Interestingly, 29% acinar PCs, 7% ductal PCs, and 46% neuroendocrine carcinomas/tumors were PD-L1+ on immunohistochemistry. Different scoring methods or cut-off criteria were applied on variable specimen-types, evaluating tumors showing different clinic-pathologic features. The positivity rate of different PD-L1 antibody clones in tumor cells ranged from 3% (SP142) to 50% (ABM4E54), excluding the single case tested for RM-320. The most tested clone was E1L3N, followed by 22C3 (most used for pembrolizumab eligibility), SP263, SP142, and 28-8, which gave the positivity rates of 35%, 11-41% (depending on different scoring systems), 6%, 3%, and 15%, respectively. Other clones were tested in <200 cases. The PD-L1 positivity rate was usually higher in tumors than benign tissues. It was higher in non-tissue microarray specimens (41-50% vs. 15%), as PC cells frequently showed heterogenous or focal PD-L1-staining. PD-L1 was expressed by immune or stromal cells in 12% and 69% cases, respectively. Tumor heterogeneity, inter-institutional preanalytics, and inter-observer interpretation variability may account for result biases.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 2: Clinic-Pathologic Correlations

Many studies have investigated the potential prognostic and predictive role of PD-L1 in prostatic carcinoma (PC). We performed a systematic literature review (PRISMA guidelines) to critically evaluate human tissue-based studies (immunohistochemistry, molecular analysis, etc.), experimental research (cell lines, mouse models), and clinical trials. Despite some controversial results and study limitations, PD-L1 expression by tumor cells may be related to clinic-pathologic features of adverse outcome, including advanced tumor stage (high pT, presence of lymph node, and distant metastases), positivity of surgical margins, high Grade Group, and castration resistance. Different PD-L1 positivity rates may be observed in matched primary PCs and various metastatic sites of the same patients. Over-fixation, type/duration of decalcification, and PD-L1 antibody clone may influence the immunohistochemical analysis of PD-L1 on bone metastases. PD-L1 seemed expressed more frequently by castration-resistant PCs (49%) as compared to hormone-sensitive PCs (17%). Some series found that PD-L1 positivity was associated with decreased time to castration resistance. Treatment with ipilimumab, cyclophosphamide/GVAX/degarelix, or degarelix alone may increase PD-L1 expression. Correlation of PD-L1 positivity with overall survival and outcomes related to tumor recurrence were rarely investigated; the few analyzed series produced conflicting results and sometimes showed limitations. Further studies are required. The testing and scoring of PD-L1 should be standardized.

Primary histiocytic sarcoma in the brain with renal metastasis causing internal ophthalmoparesis and external ophthalmoplegia in a Maine Coon cat

Case summary

An 11-year-old neutered male Maine Coon cat was presented for investigation of anisocoria and depression. Neurological examination was consistent with a lesion at the level of the middle cranial fossa, and biochemistry was indicative of moderate renal functional impairment. MRI of the brain identified an extra-axial mass lesion at the level of the middle cranial fossa, T2-weighted hyperintense and strongly homogeneously contrast enhancing with dural tail. The cat was euthanased after 6 weeks of palliative treatment with corticosteroids. Histopathology and immunohistochemistry of the brain, the intra-cranial mass and the renal masses found on necropsy were consistent with histiocytic sarcoma.

Relevance and novel information

Central nervous system histiocytic sarcoma is a rare finding in cats. This original case report describes the neurological presentation, novel MRI characteristics and pathological findings of suspected primary histiocytic sarcoma affecting the brain with renal metastasis in a cat.

New onset headache caused by histiocytic sarcoma of the spinal cord and leptomeninges: a case report

Background

Headache due to raised intracranial pressure is rarely caused by spinal lesions. We describe a patient with primary histiocytic sarcoma who presented with a new onset headache with features of raised intracranial pressure and subtle signs of cauda equina syndrome due to predominant lower spinal cord infiltration and minimal intracranial involvement.

Case

A previously well 54-year-old man presented with a 2-month history of new onset headache with features of raised intracranial pressure. Progression of lower limb weakness was delayed and mild with diagnostic delay resulting from the primary presentation with headache leading to an initial focus on cerebral pathology. Subsequent investigations revealed a previously unreported presentation of primary histiocytic sarcoma infiltrating the cauda equina causing raised intracranial pressure headache.

Conclusion

This case highlights the importance of a broad search in the investigation of new onset raised intracranial pressure headache, including imaging of the lower spinal cord. Primary histiocytic sarcoma should be considered in the differential diagnosis of this rare syndrome.

Primary histiocytic sarcoma of the central nervous system: a case report with platelet derived growth factor receptor mutation and PD-L1/PD-L2 expression and literature review

Background

Histiocytic sarcoma (HS) is an aggressive malignant neoplasm. HS in the central nervous system is exceptionally rare and associated with a poor prognosis. This report documents a case of primary HS of the central nervous system with treatment including surgery, radiotherapy, and chemotherapy.

Case presentation

Our patient was a 47 year old female presenting with progressive ataxia, headaches, imbalance, nausea, vomiting, and diplopia. MRI showed a heterogeneously enhancing lesion approximately 2.9 × 3.0 × 2.3 cm centered upon the cerebellar vermis with mild surrounding vasogenic edema and abnormal enhancement of multiple cranial nerves. The patient underwent surgical debulking, which revealed histiocytic sarcoma with grossly purulent drainage. Staging revealed diffuse leptomeningeal involvement, primarily involving the brain and lower thoracic and lumbar spine. She underwent adjuvant radiotherapy to the brain and lower spine and was started on high dose methotrexate. However, she experienced progressive disease in the cervical and thoracic spine as well as pulmonary involvement. Genomic sequencing of her tumor showed a mutation in the platelet-derived growth factor receptor A (p.V0681) which could be targeted with Dasatinib. However, she did not tolerate Dasatinib and she succumbed to progressive disseminated disease eight months from original diagnosis. Our pathologic evaluation also revealed expression of PD-L1 and PD-L2 by tumor cells raising the potential therapeutic role for immune checkpoint inhibition.

Conclusions

This case provides an example of effective CNS control with resection and moderate doses of radiation therapy. A review of the literature confirms aggressive multidisciplinary treatment is the most effective treatment against this disease. In addition, genomic sequencing may play an important role in determining new therapeutic options. However, CNS histiocytic sarcoma remains an aggressive disease with a propensity for early widespread dissemination and few long term survivors.

Case of primary central nervous system histiocytic sarcoma with prominent proliferation of histiocytic cells between the trabeculae of reactive glial cells

Histiocytic sarcoma (HS) is an extremely rare malignant neoplasm that exhibits morphologic and immune-phenotype evidence of histiocytic differentiation. The disease most commonly involves the lymph nodes, gastrointestinal tract, skin, and soft tissue, as well as in the central nervous system (CNS) being relatively rare. Here we report a case of primary CNS HS with unusual histopathological characteristics. A 65-year-old woman presented with CNS HS in the left frontal lobe region, showing two distinct histological patterns. Approximately half of the lesion displayed histological characteristics typical of HS, including diffuse invasion of large round-to-ovoid pleomorphic cells, with mitotic figures (Ki-67 index: 30%) and coagulative necrotic foci. The other half exhibited prominent proliferation of histiocytic cells between the trabeculae of reactive glial cells, with rare mitotic figures (Ki-67 index: < 1%) and no necrotic foci. There were transitions between two morphologies. The HS tumor cells and the histiocytic cells between the trabeculae of reactive glial cells possessed nearly identical histomorphologic and immunophenotypic features, although the HS tumor cells showed a more pronounced degree of cytologic atypia and mitotic activity. To our knowledge, this is the first reported case of HS with prominent proliferation of the histiocytic cells between the trabeculae of reactive glial cells. Here we present the detailed histological, immunohistochemical, and molecular findings. Investigating cases of HS may provide insight into the pathogenesis of this disease.

Primary central nervous system histiocytic sarcoma: A case report and review of literature

RATIONALE

Primary central nervous system histiocytic sarcoma (PCNSHS) is a rare lymphohematopoietic tumor with a histiocytic cell origin. To our knowledge, only 28 cases have been published in English and 2 cases in Chinese.

PATIENT CONCERNS

A 49-year-old Asian female presented to the hospital with a 2 month history of hypomnesia, odynophagia, and gait disorder. Physical examination demonstrated decreased lower extremity muscle strength. The patient denied a history of malignancy.

DIAGNOSES

Radiology demonstrated a lesion in parietal lobe with uniformenhancement. Histologic analysis showed pleomorphic tumor cells with a loose arrangement, effacing the normal brain tissue. The tumor cells exhibited abundant eosinophilic cytoplasm, highly atypical nuclei and predominant nucleoli. Immunohistochemistry revealed positive immunoreactivity for CD45, lysozyme, CD68, and CD163, and negative for pan-cytokeratin (CK), epithelial membrane antigen (EMA), glial fibrillary acidic protein (GFAP), CD3, CD20, CD1a, CD79a, CD138, oligodendrocyte transcription factor (olig2), CD15, melan-A, CD30, CD21, CD35, Human Melanoma Black-45 (HMB45), and anaplastic lymphoma kinase-1 (ALK-1). The diagnosis of PCNSHS was rendered.

INTERVENTIONS

The patient underwent complete surgical resection and adjuvant radiotherapy.

OUTCOMES

Follow-up information shows the patient died 8 months following the initial diagnosis.

LESSONS

PCNSHS is extremely rare with an aggressive clinical course. Immunohistiochemistry is necessary to make this diagnosis and to exclude other primary intracranial and lymphohematopoietic tumors. Further research is required to improve the outcome of patients with PCNSHS.

Infection or Glioma? The False Dilemma of Primary Central Nervous System Histiocytic Sarcoma

BACKGROUND

Primary central nervous system (CNS) histiocytic sarcoma is an extremely rare lymphoproliferative disorder that affects the CNS and behaves aggressively. Only 27 cases of primary CNS histiocytic sarcoma have been reported. The paucity of literature on this entity has made diagnosis and treatment difficult both for the surgeon and the pathologist.

CASE DESCRIPTION

In this case of primary CNS histiocytic sarcoma, a middle-aged woman presented from an outside institution with a supposed cerebellar abscess. Intraoperative frozen pathology was initially interpreted as high-grade glioma; however, final pathology demonstrated histiocytic sarcoma.

CONCLUSIONS

This report makes a significant contribution to the literature on this rare malignant disease by outlining a similar presentation among several cases and providing a thorough overview of existing criteria for diagnosis and management.