Clinical outcome and prognosis of dogs with histopathological features consistent with epitheliotropic lymphoma: a retrospective study of 148 cases (2003-2015)

Spontaneous Lesions of Endangered Geriatric Julia Creek Dunnarts (Sminthopsis douglasi, Archer 1979) with Emphasis in Reproductive Pathology

Julia Creek dunnarts are an endangered species of carnivorous marsupials and the focus of multiple conservation strategies involving significant resources such as captive breeding programs. Despite the relevance for conservation, no study to date has focused on evaluating geriatric diseases in dunnarts. This study describes the pathology findings in a group of one wild and thirty-five captive-born, mostly geriatric Julia Creek dunnarts that failed to produce offspring over multiple breeding periods. A total of 20 females and 16 males were submitted for a postmortem examination, with ages ranging from 9 to 42 and 12 to 42 months for females and males, respectively. Of these, 10 had unremarkable findings. The most common condition in females was cystic glandular hyperplasia (n = 8), typical of hormonal dysregulation profiles in senescence, particularly hyperestrogenism. Rarely, cutaneous disease represented by unidentified dermal round cell infiltrates was observed in females (n = 2). Primary reproductive hormonal dysregulation was also suspected in males diagnosed with testicular degeneration, aspermatogenesis and/or atrophy (n = 3). Cutaneous round cell infiltrates, possibly compatible with epitheliotropic lymphomas, were seen in males (n = 3), and 2/3 affected males also had concurrent testicular degeneration or atrophy, indicating male sex could be a predictor for lymphoid neoplasia in aged dunnarts, especially in individuals with concurrent testosterone-luteinizing hormone dysregulation as it occurs in gonadectomized animals. The role of an underlying viral etiology is also explored. This study is the first to describe major spontaneous diseases in endangered aged Julia Creek dunnarts, providing an important understanding of senescence and geriatric diseases within a conservation context.

Canine Oral Lymphoma: A Review and 3 Case Studies

Canine oral lymphoma is an infrequently diagnosed malignancy in dogs and reports in the literature are lacking. Most cases are due to epitheliotropic lymphoma, in which lesions are often multifocal and involve the skin as well as the oral cavity. Epitheliotropic lymphoma is an uncommon form of lymphoma that is characterized by neoplastic T-lymphocyte tropism for epithelial tissues. However, not all cases of oral lymphoma are due to epitheliotropic lymphoma, and B-cell disease is also possible. This article describes very different cases of oral lymphoma in dogs including the history at presentation, examination and radiographic findings, treatments, and outcomes. The cases highlight the variability in signalment, examination findings, and clinical courses that are found with oral lymphoma.

Review of Canine Lymphoma Treated with Chemotherapy-Outcomes and Prognostic Factors

While canine lymphoma is a relatively common and important disease seen by veterinarians, there are limited comprehensive reviews of the literature regarding the remission and survival times following chemotherapy, and the associated prognostic factors. This comprehensive thematic review covers the available veterinary literature covering treatment outcomes and identified prognostic factors. A lack of standardised approaches to evaluate and report the outcomes was identified, including factors that would alter the duration of responses by weeks, or occasionally months. After publication of the suggested reporting criteria, this has improved but is still not uniformly applied. The prognostic factors included for evaluation varied from as few as three to seventeen, with over 50 studies using only univariate analysis. Individual papers reported much longer outcomes than others, but assessing the outcomes overall, there has been minimal change over the last 40 years. This supports the belief that novel approaches for lymphoma therapy will be required to substantively improve outcomes.

Prognostic clinical and histopathological features of canine cutaneous epitheliotropic T-cell lymphoma

Canine cutaneous epitheliotropic T-cell lymphoma is a neoplasm with heterogeneous clinical and histopathological presentations. Survival times and responses to therapy are variable, and indicators to predict outcomes are lacking. Clinical and histopathological parameters from 176 archival cases from the University of Pennsylvania and University of Bern (2012-2018) were investigated for associations with clinical outcomes. Histopathological evaluation used digitized whole slide images and QuPath software. Cases included 107 female and 69 male dogs from 48 breeds, with a mean age of 10.4 years. Most common clinical signs were erythema (n = 131), crusting (n = 108), and scaling (n = 102). Affected sites were haired skin (n = 159), lip (n = 74), nasal planum (n = 49), and paw pads (n = 48). The median survival time (MST) was 95 days (1-850). Dogs had 4.26-fold and 2.82-fold longer MST when treated with chemotherapy and prednisone, respectively, than when receiving supportive care. Haired skin involvement (hazard ratio [HR]: 2.039, 95% confidence interval [CI]: 1.180-3.523), erosions/ulcers (HR: 1.871, 95% CI: 1.373-2.548), nodules (HR: 1.496, 95% CI: 1.056-2.118), and crusting (HR: 1.454, 95% CI: 1.061-1.994) were clinical parameters predicting poor outcomes, whereas complete posttherapeutic clinical remission (HR: 0.469, 95% CI: 0.324-0.680) and a stable disease (HR: 0.323, 95% CI: 0.229-0.456) were associated with longer survival. Histopathological features associated with the increased risk of death were extensive infiltration of the panniculus (HR: 2.865, 95% CI: 1.565-4.809), mitotic count ≥7/high-power field (HR: 3.027, 95% CI: 2.065-4.439), cell diameter ≥10.0 µm (HR: 2.078, 95% CI: 1.281-3.372), and nuclear diameter ≥8.3 µm (HR: 3.787, 95% CI: 1.647-8.707).

Evaluation of clonality from multiple anatomic sites in canine epitheliotropic T cell lymphoma

BACKGROUND

Canine epitheliotropic cutaneous T-cell lymphoma (eCTCL) is thought to represent a disease homologue to human mycosis fungoides (MF). In human MF, neoplastic cells are phenotypically consistent with resident effector memory T cells, a population that remains for an extended period within tissue without circulating. Dogs with eCTCL often present with lesions in multiple locations, raising the question of whether the neoplasm is of the same T-cell subpopulation or not.

OBJECTIVES

To characterize the antigen receptor gene rearrangements of lymphocytes from skin and blood of dogs with eCTCL to determine if neoplastic clones are identical.

ANIMALS

Fourteen dogs with eCTCL.

MATERIALS AND METHODS

Histological and immunohistochemical examination, and PCR for antigen receptor rearrangement (PARR) for T-cell receptor gamma (TRG) performed on multiple cutaneous biopsy samples and blood.

RESULTS

All skin biopsies contained cluster of differentiation (CD)3-positive neoplastic lymphocytes. Within individual dogs, all skin biopsies revealed identical TRG clonality profiles, suggesting that the same neoplastic clone was present in all sites. In the blood, a matching clone was found in six of 14 dogs, a unique clone was observed in nine of 14 dogs, and no clone was detected in two of 14 dogs.

CONCLUSIONS

These findings show that canine eCTCL lesions in multiple locations harbour the same neoplastic clone, neoplastic lymphocytes do not remain fixed to the skin and instead can circulate via blood, differing clones can be identified in skin versus blood, and circulating neoplastic cells can be detected without lymphocytosis.

Feline cutaneous lymphoma: an evaluation of disease presentation and factors affecting response to treatment

OBJECTIVES

The primary goal of this study was to characterize the clinical presentation of feline cutaneous lymphoma. The secondary aims included determining if treatment or initial response to treatment affected the overall survival of patients, and understanding if disease characteristics such as immunophenotype, cell size or the presence of epitheliotropism influenced response to treatment.

METHODS

Veterinary medical oncologists at four academic veterinary teaching hospitals submitted cases of feline patients with cutaneous lymphoma diagnosed by histopathology or cytology. Signalment, feline leukemia virus (FeLV)/feline immunodeficiency virus (FIV) status, physical examination findings, clinical signs, diagnostic tests, therapy, response and outcome, and necropsy findings, when available, were recorded.

RESULTS

Forty-one patients were identified and described. The majority of patients were domestic shorthair cats (n = 29). The median age at diagnosis was 12.3 years. Males were over-represented in the population (n = 30). In the majority of patients (n = 33), the FIV/FeLV status was unknown. Twenty patients were fully staged. Thirty-four patients were treated with a variety of modalities, including surgery, radiation, single-agent or combination chemotherapy, or prednisolone only. In multiple patients, surgery or radiation was combined with a systemic therapy. Of 34 patients treated with some form of therapy, 20 responded (achieving either a partial response or complete remission).

CONCLUSIONS AND RELEVANCE

Clinical signs and physical examination findings varied among patients. Response to therapy appeared to be associated with survival (P = 0.0025); however, this population was highly censored. Immunophenotype, cell size and the presence of epitheliotropism did not influence treatment response. Results were limited by small numbers of patients, heterogeneous disease manifestations and treatment protocols. Further studies are necessary to evaluate the effect of specific treatment modalities and disease subtype on prognosis.

Prevalence and distribution of canine neoplastic and non-neoplastic cutaneous lesions in Serbia: a retrospective study of 2432 Cases (2011 – Mid 2021)

Cutaneous lesions, especially skin tumors in dogs, are among the most common lesions in this animal species. The aim of this study was to identify the most common types of canine cutaneous lesions, to determine the absolute and relative frequency of each type of cutaneous lesion, anatomical locations, mean age, as well as gender and breed distribution. The examination included all samples of cutaneous lesions in dogs obtained by surgical biopsy in veterinary clinics and examined at the Laboratory of the Department of Pathology at the Faculty of Veterinary Medicine, University of Belgrade from the 1st January 2011 to the 1st July 2021. In this period (126 months), a total of 2432 samples of cutaneous lesions were examined, of which 1984 (81.58%) were tumors (1037/1984, 52.27% benign and 947/1984, 47.73% malignant) and 448 (18.42%) non-neoplastic cutaneous lesions. The most commonly found cutaneous tumors were: mast cell tumor (17.34% of all tumors), histiocytoma (9.78%), papilloma (7.91%), lipoma (7.81%), squamous cell carcinoma (7.36%), trichoblastoma (4.44%), hepatoid adenoma (4.39%) and malignant melanoma (4.18%). The most common non-neoplastic cutaneous lesions were: follicular cyst(s) (35.04% of all non-neoplastic lesions), pyogranulomatous chronic dermatitis (23.88%), lymphocytic dermatitis (7.37%), hyperkeratosis (4.24%), and granulomatous dermatitis (3.79%). Our results substantially confirm previously reported data regarding cutaneous neoplastic and nonneoplastic lesions in dogs, and provide updated information on their frequency, animal age, anatomic location and breed distributions.

Computed tomographic findings and clinical features in dogs with canine cutaneous lymphoma: 10 cases (2007-2018)

OBJECTIVE

To report clinical features, CT findings, treatment protocols, and outcomes for dogs in which canine cutaneous lymphoma (CCL) was diagnosed.

ANIMALS

10 client-owned dogs with CCL.

PROCEDURES

Medical records of dogs in which a diagnosis of CCL had been made between September 2007 and July 2018 and in which CT had been performed prior to treatment were reviewed. All available CT studies were reviewed, and an anatomical reference system was developed to map observed lesions. Treatment protocols and patient outcomes were summarized.

RESULTS

14 CT examinations were performed on the 10 dogs, and 9 dogs had lesions consistent with CCL on CT images. Nodular lesions were present in 8 dogs, and cutaneous or subcutaneous mass lesions were seen in 3. Well-defined, diffusely distributed, contrast-enhancing, cutaneous or subcutaneous nodules were most common; mass lesions were more variable in appearance. Nine dogs had lymphadenopathy, with the mandibular and axillary lymph nodes most commonly affected. Four dogs had confirmed nodal involvement, and 4 had confirmed visceral involvement. Nine dogs received treatment with chemotherapy, and 5 had a complete response.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that dogs with CCL may have a wide spectrum of CT findings. Many of these lesions, including affected lymph nodes, would be unlikely to be detected clinically, suggesting that CT may be a useful modality to assess the severity of disease and for guiding selection of local versus systemic treatment.

Lokivetmab improved pruritus in a dog with cutaneous epitheliotropic lymphoma

A 13-year-old spayed female Cavalier King Charles Spaniel presented with chronic swelling and pruritus on the palmar aspect of the left forepaw and on the tail. Cutaneous epitheliotropic lymphoma (CEL) was diagnosed by histopathology and immunocytochemistry. Prednisolone was initially used alone as an alternative treatment for CEL. Despite long-term corticosteroid therapy, the patient’s physiological (pruritus) and dermatological signs (alopecia, erythema, erosion, and ulceration with crust) progressed and showed no evidence of improvement. To address the worsening condition of pruritus, lokivetmab was started in combination with prednisolone. Once on lokivetmab, the pruritus steadily improved and was effective in resolving and maintaining remission. Further investigation on the critical role of IL-31 in the pruritus pathway of dogs with CEL is required.

Outcomes and prognostic factors in canine epitheliotropic and nonepitheliotropic cutaneous T-cell lymphomas

Canine cutaneous lymphoma is an uncommon lymphoma in dogs. Most canine cutaneous lymphoma cases have a T-cell origin. Canine cutaneous T-cell lymphoma (CTCL) is classified into epitheliotropic and nonepitheliotropic cutaneous lymphomas, and each type of lymphoma is subclassified into several histological subtypes. Limited information is available regarding the prognostic significance of clinical variables and histopathological subtypes in dogs with CTCL. This retrospective study aimed to investigate the influence of clinical variables and histopathological subtypes on the prognosis of dogs with CTCL. Forty-six dogs diagnosed with CTCL by histopathological examination were included. Histopathological specimens were reexamined and classified into CTCL subtypes. The influence of the type of skin lesion, histopathological subtype, haematological examination results and treatment response on the overall survival time (OS) was examined. Thirty-one dogs were diagnosed with epitheliotropic CTCL (mycosis fungoides in 28 dogs; pagetoid reticulosis in 3 dogs) and 15 dogs were diagnosed with nonepitheliotropic CTCL (anaplastic large T-cell lymphoma in 6 dogs; peripheral T-cell lymphoma, not otherwise specified, in 9 dogs). The OS of dogs diagnosed with epitheliotropic CTCL (141 days) was significantly shorter than that of dogs diagnosed with nonepitheliotropic CTCL (374 days). As clinical variables, the presence of neoplastic lymphocytes in peripheral blood, thrombocytopenia and initial chemotherapeutic response was related to prognosis. Our results demonstrated that histopathological subtype and several clinical variables were found to influence the prognosis of dogs with CTCL.

Treatment of canine cutaneous epitheliotropic T-cell lymphoma with oclacitinib: a case report

Canine cutaneous epitheliotropic T-cell lymphoma (CETL) is associated with a poor prognosis and without consistently beneficial treatment options. This case report describes a 9-year-old Staffordshire bull terrier with CETL treated with oclacitinib (0.7 mg/kg twice daily), resulting in partial remission that was maintained for three months. Further studies are warranted.

Transcriptional Differences between Canine Cutaneous Epitheliotropic Lymphoma and Immune-Mediated Dermatoses

Canine cutaneous epitheliotropic T-cell lymphoma (CETL) and immune-mediated T-cell predominant dermatoses (IMD) share several clinical and histopathological features, but differ substantially in prognosis. The discrimination of ambiguous cases may be challenging, as diagnostic tests are limited and may prove equivocal. This study aimed to investigate transcriptional differences between CETL and IMD, as a basis for further research on discriminating diagnostic biomarkers. We performed 100bp single-end sequencing on RNA extracted from formalin-fixed and paraffin-embedded skin biopsies from dogs with CETL and IMD, respectively. DESeq2 was used for principal component analysis (PCA) and differential gene expression analysis. Genes with significantly different expression were analyzed for enriched pathways using two different tools. The expression of selected genes and their proteins was validated by RT-qPCR and immunohistochemistry. PCA demonstrated the distinct gene expression profiles of CETL and IMD. In total, 503 genes were upregulated, while 4986 were downregulated in CETL compared to IMD. RT-qPCR confirmed the sequencing results for 5/6 selected genes tested, while the protein expression detected by immunohistochemistry was not entirely consistent. Our study revealed transcriptional differences between canine CETL and IMD, with similarities to human cutaneous lymphoma. Differentially expressed genes are potential discriminatory markers, but require further validation on larger sample collections.

Clinicopathological characteristics and prognostic factors for canine multicentric non-indolent T-cell lymphoma: 107 cases

Canine lymphoma, as the most common haematopoietic malignancy, encompasses a group of heterogeneous diseases and even within the T-cell immunophenotype, differences in clinical presentation and responses to treatment exist. The aim of this retrospective study was to determine outcomes and prognostic factors of 107 dogs with multicentric non-indolent T-cell lymphoma (TCL) receiving lomustine-based (70%) and non-lomustine-based (30%) treatment. The majority were Labradors, Boxers, mixed-breed dogs and Dogue de Bordeaux. Eighty-six percent were substage b, 77% had mediastinal involvement, 15% had suspected bone marrow involvement and 12% had other extra-nodal sites of disease. The overall response rate to induction therapy was 80%; dogs receiving procarbazine in the induction protocol (P = .042), dogs with neutrophil concentration below 8.7 × 10e⁹ /L (P = .006) and mitotic rate below 10 per 5 high power field (P = .013), had greater response rates. Median progression-free survival (PFS) for the first remission was 105 days; lack of expression of CD3 on flow cytometry (P < .0001) and pretreatment with steroid (P = .012) were significantly associated with shorter PFS. Median overall survival time (OST) was 136 days; co-expression of CD79a (P = .002), lack of CD3 expression on flow cytometry, presence of anaemia (P = .007), and monocytopenia (P = .002) were predictive of shorter OST. Multicentric non-indolent TCL in dogs is an aggressive cancer with new possible prognostic factors.

Subcutaneous B Cell Lymphoma in a Dog from the West Indies

A 9-year-old male castrated mixed-breed dog from the West Indies was presented for multiple, nonpainful, nodular, circumscribed, subcutaneous masses located on the dorsum, lateral thorax, head, forelimbs, and scrotum. En bloc surgical resection of a mass on the right paw, left forehead, and left medial forelimb with proportional margins was performed. Three punch biopsies were taken from the masses located along the right lateral flank. Histopathologic and immunohistochemistry (IHC) examination of the skin lesions revealed a diagnosis of subcutaneous B cell lymphoma. Thoracic radiographs and abdominal ultrasound were negative for signs of gross metastatic disease. Chemotherapeutic intervention included intravenous doxorubicin (30 mg/m²) administered at 3-week intervals for 3 treatments and oral prednisone (2 mg/kg/d) for 3 weeks. There were no complications following the chemotherapy protocol. As of 3 years, there has been no regrowth of the tumors and the patient continues to be cancer free. To date, this is the first reported case of subcutaneous B cell lymphoma diagnosed in a dog treated successfully with gross tumor resection and chemotherapy.

A case report of total skin photon radiation therapy for cutaneous epitheliotropic lymphoma in a dog

Background

Total skin electron beam radiation therapy (TSEBT) is an effective treatment for primary diffuse cutaneous lymphomas in humans. While several techniques exist, they all require significant commitment of staff time and resources. In veterinary medicine, canine-specific techniques and strategies have been adapted and delivered but deemed not “realistically” clinically implementable given the time commitment of over 2.5 h plus per fraction or have been relegated to palliative intent. Leveraging these technologies of helical tomotherapy and 3D printing, we developed and clinically implemented a radiotherapeutic treatment strategy for the management of medically refractory diffuse cutaneous lymphoma in the dog.

Case presentation

A 13.5-year-old female spayed Bichon Frise presented to the Oncology service at Texas A&M University, College of Veterinary Medicine due to the progression of diffuse cutaneous epitheliotropic lymphoma (CEL) that had failed medical management. Twenty-seven gray were delivered to the patient with a treatment time requirement under 40 min including real time monitoring of anesthesia during setup and treatment. A partial response was noticeable after four fractions and the tumor completely regressed progressively over the entire treated area by the end of therapy. A grade 1 lethargy, fatigue, weight loss, and oral mucositis and grade 2 alopecia, nail/claw changes, pruritus, scaling, anorexia, and diarrhea were noted during treatment. Additionally, a grade 3 thrombocytopenia developed after fraction eight requiring a treatment interruption of 6 weeks and prescription modification prior to treatment continuation and completion. From the beginning of total skin photon radiation therapy (TSPT) treatment until the time of the patient was euthanized unrelated to cutaneous epitheliotropic lymphoma (123 days), only one new lesion on the head was identified and confirmed by histopathology within the treated fields.

Conclusions

The proposed technique is an acceptable alternative to TSEBT that is actually clinically implementable within a palliative or definitive setting and clinical constraints, however further testing and refinement is needed to reduce hematological complications and to confirm and expand on preliminary findings.

Cutaneous epitheliotropic lymphoma in a baboon (Papio spp.): A case report and a brief literature review

Cutaneous epitheliotropic lymphoma (CEL) has not been reported in non-human primates. We report the first case of CEL in a 9-year-old baboon. The phenotype of the neoplastic cells in this baboon is similar to CEL in humans (CD3+, CD4+, CD8-) and different from dogs (CD3+, CD4-, CD8+).

Retrospective evaluation of clinical outcome after chemotherapy for lymphoma in 15 equids (1991-2017)

BACKGROUND

Prognosis associated with lymphoma in horses is poorly characterized, and treatment is often palliative. Long-term outcome after chemotherapy for horses with lymphoma is not well documented.

OBJECTIVE

To report long-term outcome of horses with lymphoma treated with chemotherapy.

ANIMALS

Fifteen equids.

METHODS

Retrospective case series. Medical record search and call for cases on the ACVIM listserv for horses treated with chemotherapy for lymphoma.

RESULTS

Fifteen cases with adequate data were identified. Complete remission was achieved in 5 horses (33.3%), partial response was achieved in 9 equids (60%), and stable disease was achieved in 1 horse. Overall response rate was 93.3% (14/15). Overall median survival time was 8 months (range, 1-46 months). Nine horses experienced a total of 14 adverse effects attributable to chemotherapy. Adverse effects were graded according to the Veterinary Cooperative Oncology Group common terminology criteria for adverse events grading system (grade 1 alopecia, n = 2; grade 1 neutropenia, n = 2; grade 1 lymphopenia, n = 3; grade 1 lethargy, n = 1; grade 2 neurotoxicity, n = 1; grade 2 colic, n = 1; grade 1 hypersensitivity, n = 1; grade 2 hypersensitivity, n = 2; grade 5 hypersensitivity, n = 1). Higher grade adverse effects most commonly were associated with doxorubicin administration (n = 4), including 1 horse that died 18 hours post-administration.

CONCLUSIONS AND CLINICAL IMPORTANCE

Chemotherapy can be used successfully for treatment of horses with lymphoma. Adverse effects, most commonly mild, occurred in approximately two-thirds of treated horses.

Clinical response to isotretinoin and interferon-α of two dogs with cutaneous epitheliotropic T-cell lymphoma: a case report

BACKGROUND

There is no specific therapy for cutaneous epitheliotropic T-cell lymphoma (CETL). The administration of retinoids in conjunction with interferon-α (IFN-α) in CETL has not been reported in dogs.

CASE PRESENTATION

Two dogs (Shih tzu and Miniature pinscher) presented with multiple nodular skin lesions. Histopathological examination revealed diffuse infiltrations of lymphocytes in the epidermis and dermis, with a CD3-positive immunophenotypic profile. Based on the clinical and histopathological examination, CETL was diagnosed. Both dogs were treated with isotretinoin in combination with IFN-α and showed clinical improvement with complete or partial remission. The disease in these dogs was well-controlled for more than 264 days of overall median survival time without any additional clinical signs after initiation of the treatment. In both the cases, the dogs were followed up for 27 months, and 10 months without any evidence of recurrence or metastasis, respectively.

CONCLUSIONS

We describe the clinical efficacy of isotretinoin combined with IFN-α in 2 dogs with CETL. Long-term management with isotretinoin combined with IFN-α was effective in treating CETL in these cases.

Prevalence of CD20+ cutaneous epitheliotropic T-cell lymphoma in dogs: a retrospective analysis of 24 cases (2011-2018) in the USA

BACKGROUND

Limited information is known about the baseline frequency of canine CD20 positive (⁺ ) cutaneous epitheliotropic T-cell lymphoma. A single canine case report has been published.

OBJECTIVES

To characterize the baseline frequency of CD20⁺ staining in cases of canine cutaneous epitheliotropic T-cell lymphoma; to assess its values as a prognostic indicator.

ANIMALS

Skin biopsies from 24 client-owned animals diagnosed with cutaneous epitheliotropic lymphoma were assessed.

METHODS AND MATERIALS

A retrospective review of medical records from 2011 to 2018. Clinical histories and previous histological and immunohistochemical slides were collected from 24 dogs and additional immunohistochemical staining was performed as needed to assess cases of cutaneous epitheliotropic T-cell lymphoma for CD3, CD20, CD79a and PAX5 staining characteristics. Staining characteristics were assessed for their statistical relationship to median survival time.

RESULTS

Overall median survival time was 189 days following the onset of clinical signs and 99 days following definitive diagnosis; 54% of cases had CD20⁺ staining. There was no statistically significant correlation between staining characteristics and median survival time from onset of signs (P = 0.54) or from diagnosis (P = 0.61).

CONCLUSIONS AND CLINICAL SIGNIFICANCE

Canine cutaneous epitheliotropic lymphoma has a higher instance of CD20 positivity than documented previously. This indicates that CD20 staining may be unsuitable to differentiate T-cell and B-cell cutaneous epitheliotropic lymphoma. This also may have therapeutic implications with the advent of canine CD20 monoclonal antibody therapies.

A retrospective study of flow cytometric characterization of suspected extranodal lymphomas in dogs

Flow cytometry (FC) is widely applied to characterize and stage nodal lymphomas in dogs because it has a short turnaround time, requires minimally invasive sampling, and allows contemporary evaluation of neoplastic cells in the primary lesion and of blood and marrow involvement. We investigated advantages and limitations of FC in suspected extranodal lymphomas in dogs. The likelihood of obtaining a suitable FC sample was significantly lower for aspirates of extranodal lesions than for lymph node aspirates. However, we noted no differences among different extranodal lesion sites. We also describe FC results for 39 samples compatible with extranodal lymphoma. A dominant population of large cells was easily identified on morphologic FC scattergrams in many cases. Phenotypic aberrancies were frequently present, mainly in T-cell lymphomas. Lymphoma cells were distinguishable from normal residual lymphocytes in >85% of cases, facilitating the quantification of putative blood and marrow involvement by FC. Despite the high percentage of non-diagnostic samples (32 of 73, >40%), we support the inclusion of FC in the diagnostic workup of suspected extranodal lymphomas in dogs, in conjunction with histopathology. Histopathology is the gold standard for diagnosing lymphoma, provides relevant information, including tissue invasion and epitheliotropism, but has a longer turnaround time.