Molecular characteristics of multifocal brain histiocytic sarcoma

Diagnostic challenges of primary central nervous system histiocytic sarcoma: case report and literature review

Histiocytic sarcoma (HS) is a rare malignant tumor that primarily affects the lymph nodes, intestines, skin, and soft tissues. Primary central nervous system histiocytic sarcoma (PCNSHS) is even rarer. We present the case of a 50-year-old Asian male with PCNSHS who was hospitalized after experiencing intermittent headaches and slurred speech for a week. During surgery, both tumor cells and purulent material were observed, and the diagnosis of PCNSHS was ultimately confirmed by immunohistochemistry. Furthermore, we conducted a literature review from 1952 to the present, screening and analyzing 49 related cases across 41 publications.

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.

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 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.