Case Report: Long-Term Response to Radiotherapy Combined With Targeted Therapy in Histiocytic Sarcoma Harboring Mutations in MAPK and PI3K/AKT Pathways

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.

Case report: Prompt response to radiotherapy and chemotherapy combined with crizotinib in gingival sarcomatoid squamous cell carcinoma with MET 14 mutation

Background

As a kind of squamous cell carcinoma of head and neck (HNSCC), gingival sarcomatoid squamous cell carcinoma (GSSCC) is a rare biphasic malignant neoplasm. To date, surgical resection was often utilized for gingival squamous cell carcinoma (GSCC), while for patients with advanced gingival carcinoma who cannot tolerate surgery, radiotherapy and chemotherapy can be regarded as a treatment strategy. Many molecular-targeted drugs were investigated and approved for the treatment of malignant diseases, including hematologic diseases and solid tumors. Although targeted therapies such as EGFR inhibitors have shown therapeutic efficacy in HNSCC, there are still some patients who cannot benefit from it. New therapeutic targets and strategies should be further explored.

Case presentation

An 83-year-old woman was referred to our hospital with left lower gingival mass for more than 1 month in June 2021. Pathologic diagnosis is sarcomatoid squamous cell carcinoma. Due to the large tumor at the time of diagnosis and poor quality of life, the patient was intolerant to surgery, so she was given radiotherapy (RT) combined with concurrent chemotherapy (CT) with albumin bound paclitaxel. According to next-generation sequencing (NGS) results (MET exon 14 skipping mutation-positive), she was treated with crizotinib, a tyrosine kinase inhibitor that targets MET. Through the comprehensive treatment, the patient’s condition promptly improved, clinical complete remission (CR) was achieved in 2 months, and 9-month progression-free survival (PFS) was obtained. She finally died from non-cancer-related diseases.

Conclusion

Here we report the treatment of a GSSCC patient with MET mutation, who responded to crizotinib promptly and positively. It provides a new reference for understanding MET abnormalities in GSSCC and offers a new idea for the targeted treatment of gingival carcinoma.

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

Histiocytic sarcoma (HS) is a rare hematological malignancy, which exhibits morphological and immunophenotypic features of histiocytes. A standard therapy for HS has not yet been established due to its rareness; therefore, disease control is not always possible. A multimodal treatment strategy has been suggested for HS. The present study reported on a case of a 43-year-old female patient who complained of left femoral pain, which was caused by left femoral bone mass. A biopsy of their left femoral bone tumor revealed that the patient had HS. Their sarcoma was localized in the femoral bone and was not considered to be curable, due to local infiltration of the bone tumor beyond the periosteum. The patient then underwent two types of HS-specific chemotherapy; however, both regimens were ineffective. As a result, they underwent radiation therapy at the sites of progressive disease. Because the HS cells of the patient expressed PD-L1, they were treated with nivolumab (240 mg/body, biweekly) for residual diseases in the right occipital bone, multiple lung nodules, intrapelvic right lymph node and primary site. Nivolumab treatment resulted in a complete response at all sites, with the exception of the primary site, which was confirmed by ¹⁸F-fluorodeoxyglucose-positron emission tomography/computed tomography. The patient received additional nivolumab treatment as consolidation therapy for 1 year. In addition, residual disease of the femoral head was completely resected. The surgically resected refractory tumor revealed the tumor cells no longer pathologically expressed PD-L1 . In conclusion, for refractory and recurrent HS in which surgical resection is not appropriate, treatment with immune-checkpoint inhibitors, such as nivolumab, may be considered an optional but promising immunotherapy if the tumor histologically expresses PD-L1. The present study detected one of the refractory mechanisms of ICI treatment.