High-field MRI using standard pulse sequences has moderate to substantial interobserver agreement and good accuracy for differentiation between intracranial extra-axial histiocytic sarcoma and meningioma in dogs.

Intracranial extra-axial histiocytic sarcoma shares common MRI features with meningioma. As histiocytic sarcoma carries a generally worse prognosis than meningioma, the ability to differentiate between these two neoplasms is of clinical value. The aim of this retrospective diagnostic accuracy and observer agreement study was to evaluate the accuracy and reliability of high-field MRI to differentiate between these two tumors, using standard pulse sequences and published MRI features. A total of 51 dogs were included (26 meningiomas and 25 histiocytic sarcomas). Magnetic resonance imaging examinations were independently assessed by three experienced board-certified radiologists, evaluating 18 imaging features. They were asked to assign each case to one of three categories (meningioma, histiocytic sarcoma, and undetermined). Agreement for the MRI diagnosis across all three reviewers was moderate (κ 0.54) while paired interobserver agreement ranged from moderate to substantial (κ 0.58-0.74) with percent agreement ranging between 86.1% and 87.7%. Overall, the probability of correctly diagnosing meningioma in a dog with this tumor ranged between 79.2% and 94.4%, and the probability of correctly diagnosing histiocytic sarcoma in a dog with this tumor ranged between 76.0% and 92.3%. The overall probability to diagnose the correct tumor, irrespective of type, ranged between 79.2% and 89.7%. Histiocytic sarcomas tended to have more extensive edema and more often had combined perilesional and distant meningeal enhancement affecting both pachy- and leptomeninges, while for meningiomas, meningeal enhancement tended to more commonly be perilesional and pachymeningeal. Imaging features that seemed more useful to make a correct diagnosis included "location/type of meningeal enhancement," "osseous changes in the adjacent neurocranium," "cystic changes," and "herniation severity."

Leukemic Phase of Histiocytic Sarcoma of the Digestive System: A Rare Manifestation of a Rare Disease.

Histiocytic sarcoma (HS) is a rare, malignant, and aggressive subtype of histiocytosis. We present an unusual case of aggressive HS presenting in the gastrointestinal tract and gallbladder that progressed after several lines of chemotherapy with a leukemic phase. We review the clinical, pathological, and molecular characteristics of HS in this case and review the literature on HS involving the digestive system as well as on overt leukemic phase of this disease. HS is often diagnosed at an advanced stage, and mortality is high. We discuss the therapeutic approach to patients with HS. We highlight the role of overexpression and somatic alterations in the RAF-MEK-ERK pathway in the pathogenesis of HS and discuss potential targeted approaches to treat these rare tumors.

[Primary histiocytic sarcoma of the aortic valve as a trigger of heart failure in a crossbreed dog]. / Primäres histiozytäres Sarkom der Aortenklappe als Auslöser von Herz­versagen bei einem Mischlingshund.

INTRODUCTION: A case of a histiocytic sarcoma at the aortic valve with multiple metastases in the ventricular myocardium, ventricular endocardium and mitral valves in a male crossbreed dog is described. Neoplasia resulted in intermittent forward heart failure, thrombosis, myocardial infarction, and ventricular tachycardia.

INTRODUCTION: On décrit le cas, chez un chien croisé, d'un sarcome histiocytaire de la valvule aortique avec de multiples métastases dans le myocarde ventriculaire, l'endocarde ventriculaire et la valvule mitrale. Le néoplasie conduisait à une faiblesse, à des thromboses et des infarctus du myocarde ainsi qu'à une tachycardie ventriculaire.

Canine histiocytic sarcoma presenting as a target lesion on brain magnetic resonance imaging and as a solitary pulmonary mass.

A 6-year-old spayed female miniature schnauzer presented with generalized seizures and progressive multifocal intracranial neurologic disease. Thoracic radiographs and computed tomography (CT) revealed a large solitary pulmonary mass within the right cranial lung lobe. On brain magnetic resonance imaging (MRI), a solitary intraparenchymal mass within the left piriform lobe had a "target" appearance on both pre- and postcontrast sequences. Cerebrospinal fluid was unremarkable and histopathology indicated both masses represented histiocytic sarcoma. This case represents an uncommonly reported MRI appearance of histiocytic sarcoma in the canine brain and a large, solitary-appearing pulmonary histiocytic sarcoma in the same dog.

Comparisons among MRI signs, apparent diffusion coefficient, and fractional anisotropy in dogs with a solitary intracranial meningioma or histiocytic sarcoma.

Although MRI has become widely used in small animal practice, little is known about the validity of advanced MRI techniques such as diffusion-weighted imaging and diffusion tensor imaging. The aim of this retrospective analytical observational study was to investigate the characteristics of diffusion parameters, that is the apparent diffusion coefficient and fractional anisotropy, in dogs with a solitary intracranial meningioma or histiocytic sarcoma. Dogs were included based on the performance of diffusion MRI and histological confirmation. Statistical analyses were performed to compare apparent diffusion coefficient and fractional anisotropy for the two types of tumor in the intra- and peritumoral regions. Eleven cases with meningioma and six with histiocytic sarcoma satisfied the inclusion criteria. Significant differences in apparent diffusion coefficient value (× 10-3 mm2 /s) between meningioma vs. histiocytic sarcoma were recognized in intratumoral small (1.07 vs. 0.76) and large (1.04 vs. 0.77) regions of interest, in the peritumoral margin (0.93 vs. 1.08), and in the T2 high region (1.21 vs. 1.41). Significant differences in fractional anisotropy values were found in the peritumoral margin (0.29 vs. 0.24) and the T2 high region (0.24 vs. 0.17). The current study identified differences in measurements of apparent diffusion coefficient and fractional anisotropy for meningioma and histiocytic sarcoma in a small sample of dogs. In addition, we observed that all cases of intracranial histiocytic sarcoma showed leptomeningeal enhancement and/or mass formation invading into the sulci in the contrast study. Future studies are needed to determine the sensitivity of these imaging characteristics for differentiating between these tumor types.

Orbital histiocytic sarcoma in a 2-year-old child.

Histiocytic sarcoma (HS) is an exceedingly rare hematologic malignancy that typically presents in the skin, gastrointestinal tract, and lymph nodes. Few cases of HS have been reported in the head and neck. This study describes the case of a 2-year-old girl presenting with 2 weeks of left lower eyelid swelling. Diagnostic testing and biopsy revealed a large inferior orbital mass causing severe bony destruction with extension into the sinuses. Pathologic analysis revealed classic features of HS. To the best of knowledge, no previous case of HS occurring in the orbit of a child has been reported. This study presents an exceedingly rare case of HS in a young child presenting with eyelid swelling. In addition, this case report is in compliance with HIPAA regulations.

Radiographic characterization of primary lung tumors in 74 dogs.

Primary pulmonary neoplasia is well recognized in dogs and prognosis depends upon the tumor type. The purpose of this retrospective study was to characterize the radiographic appearance of different primary lung tumors with the goal of establishing imaging criteria to separate the different types. Three-view thoracic radiographs of 74 dogs with histologically confirmed pulmonary anaplastic carcinoma (n = 2), adenocarcinoma (n = 31), bronchioalveolar carcinoma (n = 19), histiocytic sarcoma (n = 21), and squamous cell carcinoma (n = 1) were evaluated. Radiographs were assessed for tumor volume, affected lobe, location within lobe, overall pulmonary pattern, presence of cavitation, mineralization, air bronchograms, lymphadenomegaly, and pleural fluid. Histiocytic sarcomas were significantly larger than other tumor types (271 cm(3); P = 0.009) and most likely to be found in the left cranial (38%; 8/21) and right middle (43%; 9/21) lung lobes, whereas adenocarcinomas were most likely to be found in the left caudal (29%; 9/31) lung lobe. Fifty-seven percent (12/21) of histiocytic sarcomas had an internal air bronchogram. Findings indicate that a large mass in the periphery or affecting the whole lobe of the right middle or left cranial lung lobe with an internal air bronchogram is likely to be an histiocytic sarcoma.

FDG PET/CT Imaging of Liver and Spleen Histiocytic Sarcoma.

ABSTRACT: Histiocytic sarcoma is a tumor of the lymphohematopoietic system characterized by macrophage morphology and immunophenotype. Here, we report FDG PET/CT images of a 50-year-old man with coexisting histiocytic sarcoma of the liver and spleen. Images showed multiple enhanced uptake lesions of FDG in both the liver and spleen. Ultimately, histiocytic sarcoma was confirmed by the biopsy histopathology.

Unusual presentation of a rare cancer: histiocytic sarcoma in the brain 16 years after treatment for acute lymphoblastic leukemia.

Histiocytic sarcoma (HS) is a very rare hematopoietic neoplasm that has been reported in association with other hematological malignancies. Presentation of HS in the central nervous system is even less common. Diagnosis of HS requires the presence of histiocytic markers and the systematic exclusion of markers of other cell lineages. Primary HS central nervous system tumors are aggressive and generally have poor outcomes. There are no standard treatment guidelines due to lack of clinical trials and a limited number of case reports. Here we present a unique case with two primary histiocytic lesions in the brain, refractory to systemic and radiation therapies, that developed after being treated for T-cell acute lymphoblastic leukemia 16 years prior.

Histiocytic sarcoma of the palate: a case report.

Histiocytic sarcoma is a malignant proliferation of cells that exhibit morphological and immunophenotypic features of mature histiocytes. Owing to its rarity, its clinical features and standard treatment have not yet been established. This report describes a case of histiocytic sarcoma of the palate that developed in a 76-year-old man, the first report of an intraoral histiocytic sarcoma. An extended resection was performed; however, establishing the excision line was extremely difficult because assessing the tumour boundary on imaging was challenging and the tumour underwent dynamic gross morphological changes following biopsy. Complete resection is required to obtain a favourable prognosis for high-grade tumours with indistinct borders. In this case, an intraoperative rapid examination with frozen section analysis was performed along the planned excision line to completely resect the tumours exhibiting such behaviour. At 28 months postoperatively, the patient demonstrated no recurrence or metastasis; however, he is under careful monitoring.

Rare Multisystem Histiocytic Sarcoma on 18F-FDG PET/CT.

Histiocytic sarcoma (HS) is a rare malignancy with morphologic and immunophenotypic features indicating histiocytic differentiation. We present a case of HS with multisystem involvement, including an obstructing mass in the pancreatic head. 18F-FDG PET/CT is a valuable tool in staging this rare entity and in assessing the response to therapy. Knowing the diverse metastatic pattern of HS will help avoid imaging pitfalls on clinical 18F-FDG PET/CT scans.

Case report: Haemophagocytic histiocytic sarcoma in an english setter.

A 4-year-old English setter presented with a 1-week history of anorexia, lethargy and occasional vomiting. Blood analysis revealed moderate regenerative anaemia, mild monocytosis, thrombocytopaenia, hypoproteinaemia, hypoglobulinaemia, hypocholesterolaemia and increased C-reactive protein. On ultrasonography, the spleen had multifocal hypoechoic lesions. Fine needle aspirates from the spleen and liver showed marked extramedullary haematopoiesis, an increased number of histiocytes, haemosiderin deposits and erythrophagocytosis. A tentative diagnosis of haemophagocytic histiocytic sarcoma (HHS) was made, and the owners elected euthanasia. On autopsy, the liver and spleen were enlarged. The spleen had an uneven surface and a yellow-tan spotted appearance. Histologically, the red pulp was highly cellular and dominated by erythroid cells, as well as a population of larger polygonal cells and aggregates of histiocytes. HHS was confirmed by CD11d immunolabelling. This represents the first documented case of HHS in an English setter.

Nodal histiocytic sarcoma with prominent eosinophilic infiltration: expression of eotaxin-2 on tumor cells.

BACKGROUND: Histiocytic sarcoma (HS) is a rare neoplasm showing morphological and immunophenotypic features of mature tissue histiocytes. We report a patient with nodal HS exhibiting prominent reactive eosinophilic infiltration. CASE PRESENTATION: A 68-year-old man presented with intermittent left lower abdominal pain and weight loss over 3 months. A computed tomography scan revealed multiple abdominal nodules. Open biopsy of the mesenteric tumors was performed for definitive diagnosis. Histologically, the tumor was comprised of a diffuse noncohesive proliferation of pleomorphic large cells, including multinucleated cells. Neoplastic cells were positive for histiocytic markers (CD68, CD163, and LIGHT) and PD-L1 but lacked markers of Langerhans cells, follicular dendritic cells, and epithelial cells. Frequent reactive inflammatory cells were intermingled in the background. Interestingly, prominent eosinophilic infiltration was also noted. Spindle neoplastic cells were prone to be present around areas with little to no eosinophilic infiltration and exhibiting fibrosis and lymphatic vessel proliferation. Conversely, polygonal neoplastic cells were prone to be present around areas with relatively large amounts of eosinophilic infiltration without fibrosis or lymphatic vessel proliferation. Immunohistochemically, the tumor cells and reactive eosinophils expressed eotaxin-2 and eotaxin-3, respectively. CONCLUSION: We revealed that eotaxins induced the selective migration of eosinophils into tissues in this case. These eosinophils may affect the tumor remodeling and tumor biology characteristics of HS, such as fibrosis and lymphatic vessel proliferation.

A metastatic histiocytic sarcoma case with primary involvement of the tonsil.

Histiocytic sarcoma (HS) is an extremely rare and aggressive hematopoietic tumor. Although it can be seen at any anatomic location, the most common primary sites are skin as extranodal region, locations including the lymph nodes and gastrointestinal tract. To the best of our knowledge, in light of PubMed search, this is the first primary tonsillar HS case presented with disseminated metastases at the time of diagnosis. A 58-year-old male patient applied with swelling on the right side of the neck, difficulty in swallowing, and weight loss. Positron emission tomography computed tomography was performed and increased pathological 18F fluorodeoxy D glucose uptake was detected in the right palatine tonsil, bilateral cervical multiple lymph nodes, liver masses, intra abdominal lymph nodes, and nodular lesion in the left adrenal gland. Tonsillectomy was performed and the pathological result was reported as HS. The patient did not respond to any treatment and had died after 5 months from the date of diagnosis. In conclusion, HS is generally diagnosed at advanced stage, it has limited chemotherapy response and high mortality rates. To understand this rare disease's pathophysiological and clinical features, further investigations are needed.

Development of an Orthotopic Intrasplenic Xenograft Mouse Model of Canine Histiocytic Sarcoma and Its Use in Evaluating the Efficacy of Treatment with Dasatinib.

Canine histiocytic sarcoma is a highly aggressive and metastatic hematopoietic neoplasm that responds poorly to currently available treatment regimens. Our goal was to establish a clinically relevant xenograft mouse model to assess the preclinical efficacy of novel cancer treatment protocols for histiocytic sarcoma. We developed an intrasplenic xenograft mouse model characterized by consistent tumor growth and development of metastasis to the liver and other abdominal organs. This model represents the metastatic or disseminated form of canine histiocytic sarcoma, which is considered the most clinically challenging form of the disease. Transfection of tumor cells with a luciferase vector supported the use of in vivo bioluminescence imaging to track tumor progression over time and to assess the response of this murine model to novel chemotherapeutic agents. Dasatinib treatment of the mice with intrasplenic xenografts decreased tumor growth and increased survival times, compared with mice treated with vehicle only. Our findings indicate the potential of dasatinib for the treatment of histiocytic sarcoma in dogs and for similar diseases in humans. These results warrant additional studies to clinically test the efficacy of dasatinib in dogs with histiocytic sarcoma.