Flow Cytometry for the Detection and Quantification of Mast Cells in Lymph Nodes: A Prospective Study in 64 Dogs With Mast Cell Tumour.

Nodal metastasis is a negative prognostic factor in dogs with mast cell tumours (MCTs), thus early detection enables more informed decision-making and provides valuable prognostic information. The aim of this study is to assess the concordance between histopathologic findings of LNs and cytology and flow cytometry (FC), respectively, and to evaluate the ability of FC to differentiate between metastatic (HN2-HN3) and non-metastatic (HN0-HN1) LNs. Overall, 117 LNs from 64 dogs with first occurring MCTs were submitted for cytology, histology and FC. LNs were cytologically and histologically classified according to Krick and Weishaar systems, respectively. Using FC, mast cells (MCs) were identified as IgE+ CD117+ CD5- CD21- cells and quantified as a percentage. When compared with histologic classification, cytology showed an accuracy of 88.2% in distinguishing between metastatic and non-metastatic LNs but did not detect 25.3% of metastatic cases. FC revealed an increase in the median percentages of MCs across histologic classes, progressing from HN0 to HN3. ROC curves pinpointed 0.3% as the optimal cut-off for distinguishing between metastatic and non-metastatic LNs, with an accuracy of 84.3%. A 1.1% cut-off proved valuable in identifying HN3 LNs. The combined interpretation of cytology and FC increased accuracy to 92.2%. An algorithm for guiding the combined interpretation of cytology and FC is suggested based on these findings. In conclusion, FC proves beneficial in enhancing the early detection of metastatic LNs, particularly when utilised alongside cytology. Histopathology remains essential for confirmation, enabling the discrimination of HN classes or, in doubtful cases, for the detection or exclusion of nodal metastases.

Incorporation of Biologic Variables Into the Staging for Canine Cutaneous and Subcutaneous Mast Cell Tumours: Proposal of the UBo pTNM System.

Canine cutaneous mast cell tumours (MCTs) are currently staged based on the World Health Organization (WHO) classification, which has remained unchanged since its initial formulation. Our study aimed to assess the reliability of a novel pTNM staging system, which incorporates tumour extent (T), lymph node involvement (N), presence of distant metastases (M) and the two-tier histologic grade. We analysed medical records of dogs with one or more cutaneous/subcutaneous completely staged MCT, undergoing tumour excision with lymphadenectomy, unless distant metastases were present, in which cases, medical therapy was administered. Dogs were categorized into three stages: I (T1-2N0M0), II (T1-2N1M0) and III (distant metastases). Stages I and II were further divided based on histologic grade into 'low' and 'high'. Substage b was defined as the presence of tumour diameter of ≥3 cm and/or ulceration. Of 226 dogs, 87 (38.5%) were in Stage I (I-low, n = 75; I-high, n = 12), 107 (47.3%) in Stage II (II-low, n = 59; II-high, n = 48), and 32 (14.2%) in Stage III. The newly proposed staging system was able to significantly stratify the population for both time to progression and tumour-specific survival. Compared to Stage I-low, the risk of progression increased significantly for Stage I-high (18.3 times), Stage II-low (8.5 times), Stage II-high (41.5 times) and Stage III (110.3 times). The staging system was highly prognostic for both cutaneous and subcutaneous MCTs. Prospective validation studies are essential to compare this new system with the current WHO staging and further validate its accuracy and clinical utility.

Genetic Changes in Mastocytes and Their Significance in Mast Cell Tumor Prognosis and Treatment.

Mast cell tumors are a large group of diseases occurring in dogs, cats, mice, as well as in humans. Systemic mastocytosis (SM) is a disease involving the accumulation of mast cells in organs. KIT gene mutations are very often seen in abnormal mast cells. In SM, high KIT/CD117 expression is observed; however, there are usually no KIT gene mutations present. Mastocytoma (MCT)-a form of cutaneous neoplasm-is common in animals but quite rare in humans. KIT/CD117 receptor mutations were studied as the typical changes for human mastocytosis. In 80% of human cases, the KIT gene substitution p.D816H was present. In about 25% of MCTs, metastasis was observed. Changes in the gene expression of certain genes, such as overexpression of the DNAJ3A3 gene, promote metastasis. In contrast, the SNORD93 gene blocks the expression of metastasis genes. The panel of miR-21-5p, miR-379, and miR-885 has a good efficiency in discriminating healthy and MCT-affected dogs, as well as MCT-affected dogs with and without nodal metastasis. Further studies on the pathobiology of mast cells can lead to clinical improvements, such as better MCT diagnosis and treatment. Our paper reviews studies on the topic of mast cells, which have been carried out over the past few years.

Infrequent associations of cutis marmorata telangiectatica congenita: a two-case report. / Asociaciones infrecuentes de la cutis marmorata telangiectásica congénita: reporte de dos casos.

INTRODUCTION: Cutis marmorata telangiectatica congenita (CMTC) is a rare capillary malformation characterized by persistent reticular and violaceous erythema. We present two cases of CMTC. CLINICAL OBSERVATION: The first case involved a 13-month-old male with a reticular violaceous macule on the left gluteal region and a brownish papule with Darier's sign on the inner malleolus of the left foot, which was biopsied, revealing > 15 mast cells per field, leading to a diagnosis of CMTC and solitary cutaneous mastocytoma. The second case involved a newborn with a characteristic CMTC lesion without other malformations at birth, who subsequently developed two cutaneous tumors consistent with infantile hemangiomas during follow-up. DISCUSSION: CMTC is a benign condition. However, approximately 50% of cases exhibit associated anomalies. When CMTC is suspected, musculoskeletal, ophthalmological, and cutaneous malformations should be ruled out. To the best of our knowledge, this is the first report of CMTC associated with mastocytoma and one of the few cases associated with infantile hemangioma.

INTRODUCCION: La cutis marmorata telangiectásica congénita (CMTC) es una rara malformación capilar caracterizada por eritema reticular y violáceo persistente. Presentamos dos casos de CMTC. OBSERVACION CLINICA: Un varón de 13 meses presentaba una mácula violácea reticular en glúteo izquierdo y una pápula parduzca con signo de Darier en el maléolo interno del pie izquierdo, que fue biopsiada identificando > 15 mastocitos/campo, con lo cual se diagnosticó de CMTC y mastocitoma cutáneo solitario. El segundo caso, una recién nacida con una lesión característica de CMTC sin otras malformaciones al nacer, que durante el seguimiento desarrolló dos tumoraciones cutáneas compatibles con hemangiomas infantiles. COMENTARIOS: La CMTC es una condición benigna, sin embargo, aproximadamente el 50% de los casos presentan anomalías asociadas. Ante la sospecha de CMTC se deben descartar malformaciones musculoesqueléticas, oftalmológicas y cutáneas. Hasta donde tenemos conocimiento, este es el primer reporte de CMTC asociada con mastocitoma y uno de los pocos con hemangioma infantil.

Cutaneous mastocytoma obscured by allergic contact dermatitis in an infant.

The diagnosis of solitary mastocytoma is usually made clinically, however, atypical presentations may obscure the diagnosis. We present a unique case of solitary cutaneous mastocytoma in an 11-month-old male initially misdiagnosed as atopic dermatitis; the diagnosis was obscured due to the development of an allergic contact dermatitis most likely secondary to topical medications that were being applied to the lesion. The diagnosis of solitary cutaneous mastocytoma is made based on lesion morphology, Darier's sign, and lack of systemic involvement. Most solitary cutaneous mastocytomas resolve before puberty; symptomatic treatment and avoidance of triggers are mainstay therapy.

Presencia de mastocitoma en el pabellón auricular en un canino

RESUMEN Los mastocitos cutáneos y subcutáneos son neoplasias compuestas por mastocitos que forman parte de la piel en los caninos. Es un tumor muy común y el tratamiento va enfocado a la agresividad que pudiera presentar. Ocasionalmente se puede administrar un tratamiento local, sin embargo, este no debe considerarse en pacientes con metástasis. La estadificación del tumor es de gran importancia para dar un diagnóstico, tratamiento y pronóstico para aquellos pacientes afectados por esta patología. En este trabajo se presenta el caso clínico de un canino Pastor Alemán de 11 años con la presencia de una estructura ulcerada en el pabellón auricular derecho. Se realizó diagnóstico por citología e histopatológico de mastocitoma canino grado II y baja malignidad de acuerdo con la clasificación de Pakiel. Al paciente se le realizó una resección parcial del pabellón auricular con presencia de bordes limpios en los resultados del estudio histopatológico. El objetivo de este trabajo es reportar un caso clínico con la presencia de mastocitoma en el pabellón auricular en un perro doméstico.

ABSTRACT Cutaneous and subcutaneous mast cells tumor are neoplasms composed of mast cells that are part of the skin in canines. It is a very common tumor and the treatment is focused on the aggressiveness that it may present. Sometimes it can be limited to local treatment, but if there are metastases, the prognosis can be favorable. Tumor staging is of great importance to give a diagnosis, treatment and prognosis for those patients affected by this pathology. In this work, we present the clinical case of an 11-year-old German shepherd canine with the presence of an ulcerated mass in the right auricle. The diagnosis was made by cytology and histopathology of canine mastocytoma grade II and low malignancy according to Pakiel's classification. The patient underwent a partial resection of the auricle with the presence of clean borders in the histopathological results. This is the first report of the presence of canine mastocytoma in the pinna in a canine.

Epidemiology of canine cutaneous round cell tumours on the canary archipelago in Spain.

In this study we undertook a comprehensive analysis of a Pet Tumour Registry of the Canary Archipelago (PTR-CA) in Spain to investigate the epidemiology of canine cutaneous round cell tumours. From a database of 2526 tumours collected from 2003 to 2020, we conducted a longitudinal analysis of the main trends in diagnosis, age, multiplicity and anatomical distribution as well as a case-control study comparing these cases with the contemporaneous canine population of the Canary Archipelago to analyse breed distribution. In line with former studies, we found histiocytomas mostly affect young dogs (2, IQR 1-5) and mast cell tumours affect middle-to-old dogs (8, IQR 6-10) with grade 1 affecting at younger ages (6.5, IQR 6-8) than both grade 2 (8, IQR 6-10 years) and grade 3 (9, IQR 7-11). Histiocytomas and plasmacytomas showed a similar anatomical distribution appearing mainly on the face, head and neck regions while mast cell tumours occur mainly on limbs and trunk. Higher risk for mast cell tumours and histiocytomas were found for Bulldog-related breeds such as Boxer (ORMCT = 23.61, CI95%: 19.12-29.15, ORHCT = 10.17, CI95%: 6.60-15.67), Boston Terrier (ORMCT 19.47, CI95%: 7.73-49.05, ORHCT 32.61, CI95%: 11.81-90.07) and Pug (ORMCT 8.10, CI95%: 5.92-11.07, ORHCT 7.87, CI95%: 4.66-13.28) while Chihuahua dogs showed significantly less risk (ORMCT 0.18, CI95%: 0.09-0.33, ORHCT 0.41, CI95%: 0.21-0.78). Notably, the Canarian Mastiff, a local breed, had a low risk of suffering from a mast cell tumour which raises the question of whether this relates to a genetic peculiarity of this breed or some husbandry and environmental factor.

High lysyl oxidase expression is an indicator of poor prognosis in dogs with cutaneous mast cell tumours.

Mast cell tumour (MCT) is one of the most frequent skin tumours in dogs. Due to their unpredictable biological behaviour, MCTs often cause several therapeutic frustrations, leading to investigation regarding prognostic markers. Lysyl oxidase (LOX) is an enzyme that promotes extracellular matrix stability and contributes to cell migration, angiogenesis and epithelial-mesenchymal transition. Its expression positively correlates with poor prognoses in several human and canine mammary cancers. The aim of this study was to characterise the immunohistochemical expression of LOX in MCT samples and compare it with histological grading and post-surgical survival. Twenty-six tumours were submitted to immunohistochemistry for LOX expression evaluation. All samples were positive for LOX, with variable percentages of cytoplasmic and nuclear positivity. Cytoplasmic positivity was significantly higher in high-grade MCTs (P = .0297). Our results indicate that high expression of cytoplasmic LOX in neoplastic mast cells is an indicator of poor prognosis for canine cutaneous MCTs.

Subcutaneous mast cell tumours: A prospective multi-institutional clinicopathological and prognostic study of 43 dogs.

BACKGROUND: Canine subcutaneous mast cell tumours (ScMCTs) reportedly have a good prognosis. However, biomarkers that can be used to predict outcome are currently limited. METHODS: A multicentre prospective study was conducted to identify new prognostic markers. Dogs with a first occurrence of ScMCT were enrolled upon primary tumour removal and regional lymphadenectomy. In the absence of metastasis, dogs were monitored, while dogs with overtly metastatic lymph nodes (histological node 3, HN3) received adjuvant vinblastine. RESULTS: Forty-three dogs were enrolled: 15 (34.9%) had at least one HN3 lymph node and received vinblastine, and 28 (65.1%) were monitored. Three tumours harboured exon 8 and 9 c-kit mutations. Eight (18.6%) dogs experienced tumour progression, and five (11.6%) died of MCT-related causes. The 1- and 2-year survival rates were 90% and 77%, respectively. Variables significantly associated with an increased risk of progression included high cytograde, a mitotic count (MC) greater than 4/10 high-power fields (hpf) and Ki67-index greater than 23. An MC greater than 4/10 hpf was also associated with an increased risk of tumour-related death. LIMITATIONS: Regional rather than sentinel lymphadenectomy was performed in these dogs. Dogs were enrolled in oncology referral centres, constituting a different population compared to previous studies. CONCLUSIONS: ScMCTs have a good prognosis. However, the metastatic rate at admission was higher in this study than previously reported, and a subset of tumours were associated with a fatal outcome despite multimodal treatment. Proliferative activity and cytograding may predict more aggressive behaviour in ScMCTs.

Patterns of nodal metastases, biological behaviour and prognosis of canine mast cell tumours of the pinna: A multi-institutional retrospective study.

Canine cutaneous mast cell tumours (cMCTs) of the pinna have been associated with an aggressive biological behaviour, although data remain scarce. The knowledge acquired over the past years on histologic gradings, and the value of lymph node (LN) staging, may help in better characterizing this anatomical presentation. The first aim was to describe the frequency, location, and histologic appearance of LN metastases in cMCT of the pinna. A second aim was to evaluate prognosis. Medical records of dogs with cMCT of the pinna, that underwent tumour and sentinel (SLN) or regional LN (RLN) excision, were reviewed. The influence of potential prognostic variables on time to progression (TTP) and tumour-specific survival (TSS) was investigated. Thirty-nine dogs were included: 19 (48.7%) had Kiupel high-grade (K-HG) and 20 (51.3%) had low-grade (K-LG) MCTs. Eighteen (46.1%) dogs underwent SLN mapping: the superficial cervical LN was at least one of SLN in 17 (94.4%) cases. Twenty-two (56.4%) dogs had LN metastases; the superficial cervical LN was always involved. On multivariable analysis, only K-HG was associated with increased risk of progression (p = .043) and tumour-related death (p = .021). Median TTP and TSS were 270 and 370 days in K-HG, respectively; these were not reached in dogs with K-LG tumours (p < .01). cMCTs of the pinna are often K-HG and are also associated with a higher frequency of LN metastasis; however, we confirmed the independent prognostic value of histologic grading. A multimodal treatment may lead to favourable long-term outcome. Moreover, the superficial cervical LN is most often the SLN.

[Solitary mast cell tumor. A case comunication]. / Mastocitoma solitario. Comunicación de un caso.

BACKGROUND: The solitary cutaneous mastocytoma is a variant of cutaneous mastocytosis which carries a good prognosis. It may develop at a very early age, during the first weeks of life, or even be congenital. Typically, they present as red-brownish lesions that may be asymptomatic or present systemic manifestations associated with histamine release. CASE REPORT: A 19-year-old female patient who attended a medical consultation for a pigmented lesion, slightly raised in the left antecubital fold, asymptomatic, of recent appearance and progressive growth. Dermoscopy reported a fine symmetrical network, yellowish-brown in color and randomly distributed black dots. The pathology report and immunohistochemical findings were consistent with mast cell tumor. CONCLUSIONS: The solitary cutaneous mastocytoma should not be considered as an exclusive entity in the pediatric population. Acknowledgment of its atypical clinical presentation with its dermatoscopic features, is useful for diagnosis.

ANTECEDENTES: El mastocitoma solitario es una variante de mastocitosis cutánea de buen pronóstico, congénita, que aparece durante las primeras semanas de vida. Las manifestaciones clínicas incluyen: lesiones de color rojo-marrón, que pueden ser asintomáticas o generar lesiones sistémicas asociadas con la liberación de histamina. REPORTE DE CASO: Paciente femenina de 19 años, que acudió a consulta médica por una lesión pigmentada, ligeramente sobreelevada en el pliegue antecubital izquierdo, asintomática, de reciente aparición y crecimiento progresivo. La dermatoscopia reportó una fina red simétrica, de color pardo-amarillenta, con puntos negros y distribución al azar. El informe de Anatomía patológica y los hallazgos de inmunohistoquímica fueron compatibles con mastocitoma. CONCLUSIONES: El mastocitoma solitario no es exclusivo de la población pediátrica y su manifestación en la población adulta suele ser atípica. El conocimiento de las características dermatoscópicas es útil para establecer el diagnóstico certero.

Mastocitosis crónica. Presentación de un caso y revisión de la literatura

La mastocitosis cutánea crónica es una genodermatosis de etiología desconocida y que se encuentra dentro del grupo de enfermedades raras o poco frecuentes. Se caracterizan por el crecimiento y acumulación de causa desconocida de mastocitos en piel y otros órganos y se manifiesta como una urticaria pigmentosa. Se presenta el caso de un paciente de sexo masculino, con lesiones eritematopapulosas en región de las manos que fue extendiéndose a todo el cuerpo y cuero cabelludo que al desaparecer quedaban manchas hipercrómicas con signo de Darier positivo. Se confirmó el diagnóstico de urticaria pigmentosa mediante biopsia de la piel. Es una enfermedad rara con una baja incidencia, la forma cutánea tiene un pronóstico favorable, por lo que resulta de vital importancia conocer y diagnosticar de forma precoz esta entidad con un manejo multidisciplinario para prevenir las manifestaciones sistémicas que aparecen. Llevar un tratamiento sintomático permitirá una mejor calidad de vida en los infantes. Se presenta el caso porque al considerarse la mastocitosis una enfermedad rara la prevalencia e incidencia de estos casos es muy baja.

Chronic cutaneous mastocytosis is a genodermatosis of unknown etiology and that is within the group of rare or infrequent diseases. They are characterized by the growth and accumulation of mast cells in the skin and other organs of unknown cause and manifest as urticaria pigmentosa. The case of a male patient is presented, with erythematopapular lesions in the region of the hands that spread to the entire body and scalp that, when they disappeared, left hyperchromic spots with Darier's sign: positive. The diagnosis of urticaria pigmentosa was confirmed by skin biopsy. It is a rare disease with a low incidence, the cutaneous form has a favorable prognosis, so it is of vital importance to know and diagnose this entity early with a multidisciplinary management to prevent the systemic manifestations that appear. Taking a symptomatic treatment will allow a better quality of life in infants. The case is presented because mastocytosis is considered a rare disease, the prevalence and incidence of these cases is very low.

Mast Cell Sarcoma of Small Intestine, Early Diagnosis, and Good Prognosis: An Extremely Rare Case Report and Review of the Literature.

Gastrointestinal mast cell sarcoma is a rare variant of mastocytosis. It is a unifocal tumor with high destructive capacity and metastatic potential. Diagnosis of mast cell sarcoma can be challenging and might be so delayed that unfavorable prognosis may be expected. In this case report, we will describe our experience with a case of mast cell sarcoma in the small intestine of an elderly woman, which was diagnosed early on throughout the course of her disease and successfully treated. The patient was a 59-year-old woman who presented with abdominal pain, flushing, weight loss, and vomiting. Imaging studies supported the existence of an infiltrative neoplasm in the jejunum. Then, surgical removal of the tumor was performed. The presence of mast cells in the resected tumor was confirmed by immunohistochemistry, histopathology, and Giemsa staining. After almost a year of follow-up, the patient's overall condition was fine, and no signs of recurrence were found. This is the first reported case of successfully treated gastrointestinal mast cell sarcoma. All of the previously reported cases had been diagnosed after recurrence with no response to treatment. Our case shows the significance of early diagnosis and treatment in this condition and its impact on outcome and prognosis. That could be achieved only if the pathologist has a high suspicion for this rare disease and keeps it in the back of one's mind.

CT features of subcutaneous, intermuscular, and intramuscular mast cell tumors in dogs.

Surgical removal is the treatment of choice for subcutaneous (SC), intermuscular (InterM), and intramuscular (IntraM) mast cell tumors (MCTs). Advanced imaging (CT or MRI) is frequently used for presurgical planning, but InterM and IntraM MCTs can be difficult to identify and delineate on CT. Aims of the current retrospective, diagnostic accuracy, observer agreement study were to describe the imaging features of SC, InterM, and IntraM MCTs on CT and to assess the limitation of CT to identify the full local extent of the MCT. Inclusion criteria for the study were dogs with a cytologically or histologically diagnosed MCTs determined to be SC, InterM, or IntraM MCT based on histology and/or a CT scan performed in the gross disease setting. Two board-certified veterinary radiologists reviewed the CT images and recorded location, contrast enhancement pattern, and delineation between the normal and abnormal tissue. Sensitivity and specificity of CT for determining location (SC/InterM versus IntraM) was 85.71% and 55.56%, respectively, when compared to consensus location based on surgical pathology report/CT/MRI review. There was a low inter-rater agreement for delineation (kappa: 0.150 (-0.070 to 0.370) and measurement had a low/moderate correlation (rho: 0.4667 to 0.5792). Upon review by a surgical oncologist, CT findings were deemed insufficient for curative surgical planning in 13 of 16 due to inadequate definition of tumor depth, compartment boundary (fascial plane) or MCT margins. The use of CT for presurgical planning of SC/InterM/IntraM MCT dogs has limitations, especially when differentiating MCT from the adjacent muscle.

Large Congenital Cutaneous Mastocytoma Presenting With Recurrent Persistent Blistering: A Case Report.

Congenital cutaneous mastocytoma is an uncommon disorder characterized by abnormal proliferation of mast cells. It typically presents as a single, small, yellowish-brown plaque, and its diagnosis is generally facilitated by distinctive clinical features, including a positive Darrier's sign. This report presents a case of an unusually large, solitary congenital mastocytoma encompassing nearly the entire circumference of the calf, observed in a newborn boy of Bangladeshi origin. Measuring 13x6 cm, the lesion formed large bullae and subsequent erosions. The perplexing clinical appearance prompted a skin biopsy, revealing monomorphic CD117 (c-KIT) positive infiltration without significant cell pleomorphism, confirming the diagnosis of cutaneous mastocytoma. The patient underwent management with potent and very potent topical steroids, oral antihistamines, and non-adhesive dressings, remaining under long-term follow-up with secondary care dermatology. In reporting this case, our objective is to augment the existing scientific literature by providing additional evidence that cutaneous mastocytomas can display a spectrum of clinical presentations, as illustrated in this case.

[A CHILD CASE OF DIFFUSE CUTANEOUS MASTOCYTOSIS].

Cutaneous mastocytosis (CM) usually appears in childhood and improves substantially before adolescence. The c-KIT mutation of D816V is present in 36% and 20% of patients with childhood-onset CM and diffuse cutaneous mastocytosis (DCM), respectively. In some cases of childhood-onset DCM, the disease can progress to systemic mastocytosis; in others, it resolves spontaneously. Thus, assessing the prognosis is difficult. Herein, we described a case of DCM in an 11-month-old, male patient without a c-KIT mutation. The patient presented with dark brown macules and sporadic erythema topped by bullous lesions. A skin biopsy of the macule on the abdomen revealed accumulation of mast cells which were round to oval-shaped with amphophilic cytoplasm within the upper dermis. The patient had received H1 inhibitor until age 3 years and continued to experience blisters on the trunk. However, no severe symptoms, such as anaphylaxis, occurred. Included in this manuscript is a review of previous reports of childhood-onset DCM in Japan and cases specifically seen at our dermatology clinic.

Histologic grade has a higher-weighted value than nodal status as predictor of outcome in dogs with cutaneous mast cell tumours and overtly metastatic sentinel lymph nodes.

In canine cutaneous mast cell tumours (cMCTs), histologic grade and clinical stage are the most important prognostic factors, with high-grade tumours and metastatic lymph nodes (LNs) significantly influencing the evolution of disease. However, it is uncertain whether histologic grade and clinical stage should be given equal weighting value in patient prognostication and management. Dogs with low- and high-grade cMCTs and at least one overtly metastatic sentinel LN undergoing standardized treatment, consisting of surgical excision of the cMCT, lymphadenectomy and chemotherapy, were retrospectively included. The aim was to determine whether, at the same clinical stage, histologic grade retained prognostic relevance. Sixty dogs were included: 26 had a high-grade cMCT tumour and 34 had a low-grade cMCT. Median follow-up was 367 days (range, 187-748) in the high-grade group, and 1208 days (range, 180-2576) in the low-grade group. Median time to progression was significantly shorter in the high-grade group than in the low-grade group (214 days versus not reached; p < .001), as well as tumour-specific survival (545 days versus not reached; p < .001). On multivariable analysis, a high histologic grade and incomplete margins retained prognostic significance for both tumour progression and tumour-specific death. In dogs with cMCT and at least one overtly metastatic LN undergoing multimodal treatment, histologic grade significantly correlated with outcome. Overall prognosis was not unfavourable, even in the high-grade group, further supporting that a multimodal therapeutic approach, addressing primary tumour and sentinel LN, should be offered. Whether chemotherapy should be incorporated in the therapeutic planning of low-grade cMCTs remains to be defined.

Multiplex genome editing of mammalian cells for producing recombinant heparin.

Heparin is an essential anticoagulant used for treating and preventing thrombosis. However, the complexity of heparin has hindered the development of a recombinant source, making its supply dependent on a vulnerable animal population. In nature, heparin is produced exclusively in mast cells, which are not suitable for commercial production, but mastocytoma cells are readily grown in culture and make heparan sulfate, a closely related glycosaminoglycan that lacks anticoagulant activity. Using gene expression profiling of mast cells as a guide, a multiplex genome engineering strategy was devised to produce heparan sulfate with high anticoagulant potency and to eliminate contaminating chondroitin sulfate from mastocytoma cells. The heparan sulfate purified from engineered cells grown in chemically defined medium has anticoagulant potency that exceeds porcine-derived heparin and confers anticoagulant activity to the blood of healthy mice. This work demonstrates the feasibility of producing recombinant heparin from mammalian cell culture as an alternative to animal sources.

Carboxypeptidase A3 expression in canine mast cell tumors and tissue-resident mast cells.

Mast cell tumors (MCTs) are one of the most common cutaneous malignancies in dogs. Previous studies have reported expression of mast cell-specific proteases chymase and tryptase in canine cutaneous MCTs and in connective tissue and mucosal mast cells. In humans and rodents, mast cells express an additional specific protease, carboxypeptidase A3 (CPA3). In this article, we describe CPA3 immunoreactivity in connective tissue, visceral, mucosal, and neoplastic mast cells in dogs. Positive immunolabeling for CPA3 was observed in nonneoplastic mast cells in 20/20 formalin-fixed paraffin-embedded normal tissues (skin, liver, spleen, intestine), and in 63/63 MCTs irrespective of their histological grade. CPA3 protein expression was comparable to that of c-kit in both the nonneoplastic and neoplastic mast cells. Three distinct labeling patterns (membranous, diffuse, and focal cytoplasmic) were observed for CPA3 in MCTs. The focal cytoplasmic labeling pattern was associated with high-grade MCTs staged with the Kiupel 2-tier grading criteria. We propose CPA3 as a novel immunohistochemical marker for canine mast cells in health and disease.