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.

Efficacy of vincristine as a rescue therapy for canine histiocytic sarcoma.

Canine histiocytic sarcoma (CHS) is a malignant tumor derived from macrophages and dendritic cells. Since effective chemotherapy is needed for CHS cases, we conducted this prospective study to evaluate the efficacy and adverse events of vincristine treatment as a rescue therapy for this disease. We administered vincristine to nine CHS cases that acquired resistance to lomustine or nimustine. Complete remission was achieved in one dog, partial remission in two dogs, stable disease in five dogs, and progressive disease in one dog. The median progression-free survival was 21 days (range: 7-71 days). Severe adverse effect was observed in one dog (Grade 3 thrombocytopenia). It is essential to establish novel effective treatments for CHS.

Canine Histiocytic and Hemophagocytic Histiocytic Sarcomas Display KRAS and Extensive PTPN11/SHP2 Mutations and Respond In Vitro to MEK Inhibition by Cobimetinib.

Histiocytic sarcoma (HS) is a rare and highly aggressive cancer in humans and dogs. In dogs, it has a high prevalence in certain breeds, such as Bernese mountain dogs (BMDs) and flat-coated retrievers. Hemophagocytic histiocytic sarcoma (HHS) is a unique form of HS that presents with erythrophagocytosis. Due to its rareness, the study of HHS is very limited, and mutations in canine HHS patients have not been studied to date. In previous work, our research group identified two major PTPN11/SHP2 driver mutations, E76K and G503V, in HS in dogs. Here, we report additional mutations located in exon 3 of PTPN11/SHP2 in both HS and HHS cases, further supporting that this area is a mutational hotspot in dogs and that mutations in tumors and liquid biopsies should be evaluated utilizing comprehensive methods such as Sanger and NextGen sequencing. The overall prevalence of PTPN11/SHP2 mutations was 55.8% in HS and 46.2% in HHS. In addition, we identified mutations in KRAS, in about 3% of HS and 4% of HHS cases. These findings point to the shared molecular pathology of activation of the MAPK pathway in HS and HHS cases. We evaluated the efficacy of the highly specific MEK inhibitor, cobimetinib, in canine HS and HHS cell lines. We found that the IC50 values ranged from 74 to 372 nM, which are within the achievable and tolerable ranges for cobimetinib. This finding positions cobimetinib as a promising potential candidate for future canine clinical trials and enhances our understanding of the molecular defects in these challenging cancers.

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.

Establishment of a histiocytic sarcoma cell line and anti-tumor effect of bortezomib in the African pygmy hedgehog (Atelerix albiventris).

The African pygmy hedgehog (Atelerix albiventris) is known to have a high incidence of tumor. However, investigating the tumors of this species has been constrained by the limited availability of research materials such as cell lines and genome information. In this study, we successfully established a novel cell line from a histiocytic sarcoma (HS) of an African pygmy hedgehog, allowing us to conduct a drug screening. We investigated using FDA-approved drug library screening to determine which anticancer drug this tumor cell line is sensitive to, and as a result of apoptosis experiments, bortezomib among the three proteasome inhibitors was found to induce cell death of cancer cells by significantly increasing caspase-3 cleavage (P<0.01). Thus, we elucidated that the proteasome inhibitors, particularly bortezomib, exhibit anti-tumor effects on a cell line derived from an HS in an African pygmy hedgehog through a mechanism comparable to that described in human tumors. This study reports the first characterized cell line from the African pygmy hedgehog and also highlights the potential utility of bortezomib as an anti-tumor treatment for HS in this species.

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.

Utility of the second-generation curcumin analogue RL71 in canine histiocytic sarcoma.

Canine histiocytic sarcoma is an aggressive cancer, with a high rate of metastasis. Thus, novel therapeutic approaches are needed. Synthetic analogues of curcumin have elicited potent anti-cancer activity in multiple in vitro and in vivo models of human cancer. Furthermore, the compound 3,5-bis(3,4,5-trimethoxybenzylidene)-1-methylpiperidine-4-one (RL71) has recently exhibited potent cell cycle arrest and apoptotic induction in a canine osteosarcoma cell line. To determine its potency in canine histiocytic sarcoma cells, cell viability of DH82 and Nike cells was measured using the sulforhodamine B assay. Flow cytometry was then used to analyse both cell cycle distribution and apoptosis. Of the five curcumin analogues examined, RL71, had the highest potency with EC50 values of 0.66 ± 0.057 µM and 0.79 ± 0.13 µM in the DH82 and Nike cell lines, respectively. Furthermore, RL71 at the 1x EC50 concentration increased G2/M cell cycle arrest 2-fold, and at the 2x EC50 concentration increased the number of apoptotic cells 4-fold. These findings are consistent with previous work using RL71 in both canine and human cancer cell lines. Future research should be directed on time-dependent changes, and mechanistic investigation in greater detail to elucidate RL71 mechanisms of action.

Impact of palliative-intent radiotherapy with or without chemotherapy on lameness in flat coat retrievers with localised periarticular histiocytic sarcoma - a retrospective cohort, single institution study.

Histiocytic sarcoma (HS) is a common tumour in flat coat retrievers (FCRs) often affecting periarticular tissues and joints. Palliative-intent radiotherapy, seeks to achieve local tumour control, pain relief and improve limb function. However, the effect of palliative-intent radiotherapy on analgesic levels of dogs with localised HS has not been studied. We hypothesised that palliative-intent radiotherapy could improve lameness in dogs affected by localised HS. This study aimed to assess the impact of palliative-intent radiotherapy on lameness of FCRs with localised HS. A retrospective cohort single institution study was performed. Medical records of FCR dogs with HS that received external beam radiotherapy between 2003 and 2022 were reviewed and included demographic, staging, severity of baseline lameness, therapeutic management and outcome data. Descriptive statistics, McNemar's chi-squared test, Fisher's exact test and Kaplan-Meier analysis were used for statistical analysis. Thirty-nine dogs were included with a median age of 7.2 years, 25 were male and 14 were female. HS was most commonly located in the forelimb (29 dogs, 74.3%), affecting the shoulder joint (19 dogs, 48.7%). Staging was performed in all 39 dogs with 22 (56.4%) dogs having localised HS, six (15.3%) dogs had localised HS with node metastasis and 11 (28.2%) dogs had localised HS with systemic metastasis. All dogs received palliative-intent hypo-fractionated radiation therapy, 32 (82%) dogs showed improvement in lameness. In conclusion, palliative intent radiation treatment has an analgesic effect reducing lameness or clinical signs associated with affected tumour-bearing joints.

Parthenolide As a Therapeutic for Disseminated Canine Neoplasms.

This study provides a unique translational research opportunity to help both humans and dogs diagnosed with diseases that carry dismal prognoses in both species: histiocytic sarcoma (HS), hemangiosarcoma (HSA), and disseminated mastocytosis/mast cell tumor (MCT). Although exceedingly rare in humans, these so called "orphan diseases" are relatively more common in dogs. For these and other more commonplace cancers like lymphoma (Lym), dogs are an excellent translational model for human disease due to remarkably similar disease biology. In this study, assays were performed to assess the therapeutic potential of parthenolide (PTL), a known canonical nuclear factor kappa B (NF-κB) signaling inhibitor with additional mechanisms of antineoplastic activity, including alteration of cellular reduction-oxidation balance. Canine cell lines and primary cells are sensitive to PTL and undergo dose-dependent apoptosis after exposure to drug. PTL exposure also leads to glutathione depletion, reactive oxygen species generation, and NF-κB inhibition in canine cells. Standard-of-care therapeutics broadly synergize with PTL. In two canine HS cell lines, expression of NF-κB pathway signaling partners is downregulated with PTL therapy. Preliminary data suggest that PTL inhibits NF-κB activity of cells and extends survival time in a mouse model of disseminated canine HS. These data support further investigation of compounds that can antagonize canonical NF-κB pathway signaling in these cancers and pave the way for clinical trials of PTL in affected dogs. As dogs are an excellent natural disease model for these cancers, these data will ultimately improve our understanding of their human disease counterparts and hopefully improve care for both species. SIGNIFICANCE STATEMENT: Disseminated neoplasms in human and canine cancers are challenging to treat, and novel therapeutic approaches are needed to improve outcomes. Parthenolide is a promising treatment for histiocytic sarcoma, hemangiosarcoma, and mast cell neoplasia.

Doxorubicin and zoledronate treatment in a dog with hemophagocytic histiocytic sarcoma.

A 6-year-old castrated male greyhound dog was referred for hemophagocytic histiocytic sarcoma (HHS) diagnosed following splenectomy. Severe thrombocytopenia, mild hypoalbuminemia, mild hypocholesterolemia, and mild hyperbilirubinemia were present. Abdominal ultrasound findings were concerning for hepatic metastasis. Doxorubicin and zoledronate combination therapy was initiated. The dog improved clinically and its thrombocytopenia, hypoalbuminemia, and hyperbilirubinemia resolved. The dog appeared well for 147 d before tumor progression was noted. The dog was treated with lomustine as a final measure, with no response. The dog survived for 6 mo with chemotherapy. To the authors' knowledge, this is the first report of clinical benefit of chemotherapy for HHS. Key clinical message: Doxorubicin should be considered for treating canine HHS since this variant of the disease is historically refractory to lomustine. Further research regarding efficacy of doxorubicin and zoledronate should be pursued.

Traitement à la doxorubicine et au zolédronate chez un chien atteint de sarcome histiocytaire hémophagocytaire. Un lévrier mâle castré de 6 ans a été vu pour un sarcome histiocytaire hémophagocytaire (HHS) diagnostiqué à la suite d'une splénectomie. Une thrombopénie sévère, une hypoalbuminémie légère, une hypocholestérolémie légère et une hyperbilirubinémie légère étaient présentes. Les résultats de l'échographie abdominale étaient préoccupants quant aux métastases hépatiques. Un traitement associant doxorubicine et zolédronate a été instauré. Le chien s'est amélioré cliniquement et sa thrombocytopénie, son hypoalbuminémie et son hyperbilirubinémie ont disparu. Le chien semblait en bonne santé pendant 147 jours avant de constater une progression tumorale. Le chien a été traité avec de la lomustine comme mesure finale, sans réponse. Le chien a survécu 6 mois grâce à la chimiothérapie. À la connaissance des auteurs, il s'agit du premier rapport faisant état d'un bénéfice clinique de la chimiothérapie pour le HHS.Message clinique clé :La doxorubicine doit être envisagée pour traiter le HHS canin puisque cette variante de la maladie est historiquement réfractaire à la lomustine. Des recherches plus approfondies concernant l'efficacité de la doxorubicine et du zolédronate devraient être poursuivies.(Traduit par Dr Serge Messier).

Case report: Targeting the PD-1 receptor and genetic mutations validated in primary histiocytic sarcoma with hemophagocytic lymphohistiocytosis.

Histiocytic sarcoma (HS) is a rare hematological malignancy with limited treatment options, and it is also prone to complications such as hemophagocytic lymphohistiocytosis (HLH) in the later stages of the disease, leading to difficulties in treatment and poor prognosis. It highlights the importance of developing novel therapeutic agents. Herein, we present a case of a 45-year-old male patient who was diagnosed with PD-L1-positive HS with HLH. The patient was admitted to our hospital with recurrent high fever, multiple skin rashes with pruritus throughout the body and enlarged lymph nodes. Subsequently, pathological biopsy of the lymph nodes revealed high expression of CD163, CD68, S100, Lys and CD34 in the tumor cells and no expression of CD1a and CD207, confirming this rare clinical diagnosis. Concerning the low remission rate by conventional treatment in this disease, the patient was administered with sintilimab (an anti-programmed cell death 1 [anti-PD-1] monoclonal antibody) at 200 mg/d combined with a first-line chemotherapy regimen for one cycle. Further exploration of pathological biopsy by using next-generation gene sequencing led to the use of targeted therapy of chidamide. After one cycle of combination therapy (chidamide+sintilimab, abbreviated as CS), the patient achieved a favorable response. The patient showed remarkable improvement in the general symptoms and laboratory examination results (e.g., elevated indicators of inflammation); even the clinical benefits was not persistent, he survived one more month after his cessation of treatment by himself due to economic difficulty. Our case suggests that PD-1 inhibitor coupled with targeted therapy might constitute a potential therapeutic option for primary HS with HLH.

Prolonged Survival Following Treatment of Histiocytic Sarcoma of the Canine Urinary Bladder.

A 9 yr old castrated male miniature schnauzer was diagnosed histopathologically with a mucosal histiocytic sarcoma of the urinary bladder apex, biopsied at the time of surgical cystotomy. Sequential adjuvant chemotherapy, including both lomustine (discontinued because of adverse effects) and then doxorubicin, were employed. A response to both agents was documented. Ultimately, a complete response was achieved following completion of the doxorubicin protocol. A complete response persisted 768 days following diagnosis at last follow-up. Histiocytic sarcoma of the urinary bladder remains a rare diagnosis in veterinary medicine. Only one previous case report is currently published. This case contrasts with the previous case report, which reported a survival of only 2 mo.

Near Complete Response to Trametinib Treatment in Histiocytic Sarcoma Harboring a Somatic KRAS Mutation.

Survival outcomes of patients with histiocytic neoplasms are poor, with no standard-of-care treatments available for these malignancies. Recent characterization of the genomic landscape of various histiocytic neoplasms have shown a predominance of activating driver mutations within the MAPK/ERK pathway (ie, BRAF, MEK, KRAS, MAPK, and NRAS). Subsequently, successful treatment of these malignancies with BRAF and MEK inhibitors has been reported. This report presents the first patient with histiocytic sarcoma harboring a somatic KRAS Q61H mutation who was subsequently treated to a near complete response with the MEK inhibitor trametinib. Due to patient preference, lack of standard of care treatments, and associated morbidity from head and neck dissection, initial disease reduction provided by trametinib therapy allowed for a less morbid resection. This case report highlights the utility of up-front next-generation sequencing and the efficacy of MEK inhibition in patients with histiocytic sarcoma harboring activating KRAS mutations.

Risk factors associated with the onset of lomustine-induced neutropenia in tumour-bearing dogs.

Lomustine (1-[2-chloroethyl]3-cyclohexyl-1-nitrosurea, CCNU) is an oral alkylating agent in the nitrosourea subclass that can cause myelosuppression, with neutropenia being the main dose-limiting toxicity. The aim of this study was to define the frequency of neutropenic events and to identify predisposing risk factors in tumour-bearing dogs treated with CCNU. Dogs receiving CCNU for various malignancies were identified following a search of hospital databases. Variables analysed for correlation with neutropenia included signalment, body weight, tumour type, CCNU total dose, steroid use, protocol type, use of L-asparaginase, previous anthracycline administration and use of the drug as first-line or in the rescue setting. One-hundred and fifteen cases were included; median age was 7 years (range 1-14 years) and median body weight 27.6 kg (range 3-74 kg). The median CCNU dose was 63.5 mg/m2 (range 27.7-84.9 mg/m2 ). Neutropenia occurred in 75 cases (65%) and was comprised of grade 1 (28%), 2 (16%), 3 (29.3%) and 4 (26.7%) events. Tumour type (histiocytic sarcoma [HS]), use of CCNU first line, dose >70 mg/m2 , absence of co-morbidities and previous anthracycline administration, were significantly associated with an increased risk of developing neutropenia, including high-grade events. There was a 1.7% reported mortality rate. When CCNU is used in dogs with HS, first-line, at a starting dosage >70 mg/m2 , in patients with no co-morbidities or with a history of previous anthracycline administration, there may be an increased risk of developing neutropenia. These data may help guide treatment decisions and minimize treatment delays or potentially life-threatening complications.

Outcome in dogs with curative-intent treatment of localized primary pulmonary histiocytic sarcoma.

Primary pulmonary histiocytic sarcoma (PHS) is a rare form of dendritic cell or macrophage neoplasia originating within the pulmonary parenchyma. There is limited literature describing prognosis in dogs with PHS receiving curative-intent treatment consisting of surgical excision and adjuvant chemotherapy. The primary objective of this study was to report outcomes in dogs with localized PHS treated with standardized local and systemic therapy. A secondary objective was to identify prognostic factors in this population. A multi-institutional retrospective study was performed and medical records including all surgical and histopathologic reports were retrospectively reviewed. For inclusion, dogs were required to have confirmed localized PHS and they must have undergone curative-intent surgery with resection of all gross primary tumour and enlarged tracheobronchial lymph nodes; additionally, they must have received curative-intent treatment with adjuvant single-agent CCNU chemotherapy. Twenty-seven dogs from six veterinary teaching hospitals and five private practices treated from 2008-2019 were included. The overall median survival time was 432 days. Higher CCNU dose was demonstrated to have a negative impact on survival on univariate, but not multivariable, analysis. Factors that were not found to be associated with survival on univariate analysis included body weight, breed, clinical signs at the time of diagnosis, hypoalbuminaemia, tumour size, lung lobe affected, lymph node metastasis, surgical margins and CCNU dose reductions. This study supports a favourable prognosis for dogs diagnosed with localized PHS treated with curative-intent surgery in addition to adjuvant CCNU chemotherapy and suggests that multimodal treatment may be advisable to attempt to prolong survival.

Molecular characterization of canine SHP2 mutants and anti-tumour effect of SHP2 inhibitor, SHP099, in a xenograft mouse model of canine histiocytic sarcoma.

Canine histiocytic sarcoma (HS) is an aggressive and highly metastatic neoplasm. Mutations in src homology 2 domain-containing phosphatase 2 (SHP2; encoded by PTPN11), which recently have been identified in canine HS tumour cells, could be attractive therapeutic targets for SHP099, an allosteric inhibitor of SHP2. Here, molecular characteristics of wild-type SHP2 and four SHP2 mutants (p.Ala72Gly, p.Glu76Gln, p.Glu76Ala and p.Gly503Val), including one that was newly identified in the present study, were investigated. Furthermore, in vivo effects of SHP099 on a HS cell line carrying SHP2 p.Glu76Ala were examined using a xenograft mouse model. While SHP2 Glu76 mutant cell lines and SHP2 wild-type/Gly503 mutant cell lines are highly susceptible and non-susceptible to SHP099, respectively, a cell line carrying the newly identified SHP2 p.Ala72Gly mutation exhibited moderate susceptibility to SHP099. Among recombinant wild-type protein and four mutant SHP2 proteins, three mutants (SHP2 p.Ala72Gly, p.Glu76Gln, p.Glu76Ala) were constitutively activated, while no activity was detected in wild-type SHP2 and SHP2 p.Gly503Val. Activities of these constitutively activated proteins were suppressed by SHP099; in particular, Glu76 mutants were highly sensitive. In the xenograft mouse model, SHP099 showed anti-tumour activity against a SHP2 p.Glu76Ala mutant cell line. Thus, there was heterogeneity in molecular characteristics among SHP2 mutants. SHP2 p.Glu76Ala and perhaps p.Glu76Gln, but not wild-type SHP2 or SHP2 p.Gly503Val, were considered to be oncogenic drivers targetable with SHP099 in canine HS. Further studies will be needed to elucidate the potential of SHP2 p.Ala72Gly as a therapeutic target of SHP099 in canine HS.

Disseminated mucocutaneous trichosporonosis in a patient with histiocytic sarcoma

Abstract Trichosporon asahii is the causal agent of trichosporonosis. Patients with immunosuppression or hematological malignancies are at higher risk of infection. Skin and mucosal involvement appear as fast-growing papulonodular lesions and necrotic ulcers. Internal organ dissemination is lethal. Therapeutic success depends on the underlying disease. Here, the authors present the first case of disseminated mucocutaneous trichosporonosis in a patient with a post-mortem diagnosis of histiocytic sarcoma, a rare and aggressive haematolymphoid neoplasm. Regretfully, death occurred despite treatment with liposomal amphotericin B and supportive measures, showcasing the fatality of both diseases.

Successful use of prednisolone and radiation therapy in a dog with intracranial histiocytic sarcoma.

The ideal treatment for intracranial histiocytic sarcoma (HS) remains unclear. Herein, we report a case of intracranial HS that was successfully treated using prednisolone and radiation therapy. The patient was a 9-year-old spayed female Pembroke Welsh Corgi that presented with epileptic seizures. Magnetic resonance imaging revealed a contrast-enhancing mass adjacent to the right piriform lobe. Prednisolone administration (1 mg/kg/day) decreased the lesion size. Additional palliative radiation therapy (total dose, 37 Gy) resulted in complete disappearance of the lesion. However, on day 164, the dog's neurological signs deteriorated, and she was euthanized. Necropsy revealed an intracranial metastasis of HS via the cerebrospinal fluid without any extracranial metastasis. Nonetheless, combined prednisolone and radiation therapy might be effective in treating intracranial HS.