Immunocytochemistry of bone marrow aspirates: a tool in the diagnosis of feline leukemia virus infection in cats

Feline leukemia virus (FeLV) is a highly debilitating cat pathogen due to its ability to cause many pathological changes. Therefore, identifying the virus directly in bone marrow can be a highly relevant diagnostic tool even in the absence of viraemia. The aim of this study was to compare the diagnostic efficiency of immunocytochemistry (ICC) of bone marrow aspirates with enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR). Blood samples were collected from 188 cats and separated into aliquots of whole blood for nested PCR using the U3 LTR region and the gag gene of FeLV-A as reference and serum for detection of the p27 antigen by ELISA. Bone marrow samples from these cats were placed on silanized slides for anti-FeLV ICC using gp70 as primary antibody. A total of 28.2% of the cats tested for FeLV were positive in at least one of the tests, with 26.6% positive by PCR, 18.1% by ICC and 11.2% by ELISA. Cohen's kappa agreement test revealed moderate agreement between ELISA and PCR results and substantial agreement between ICC and ELISA and between ICC and PCR. The results indicated that ICC of bone marrow is an efficient novel diagnostic test for FeLV infection.

Subcutaneous panniculitis-like T-cell lymphoma: Morphological, immunophenotypical and clonality assessment in six cats

BACKGROUND

Primary cutaneous lymphoma represents 0.2%-3% of all feline lymphomas, with nonepitheliotropic lymphomas being the most common. In humans and dogs, subcutaneous panniculitis-like T-cell lymphoma (SPTCL) is a primary nonepitheliotropic lymphoma with a T-cell phenotype developing in the subcutis and often mimicking inflammation.

OBJECTIVE

The aim of this report is to describe pathological, phenotypical and clonal features of SPTCL in cats.

ANIMALS

Six cats with SPTCL were included in this study.

MATERIALS AND METHODS

Skin biopsies were formalin-fixed, routinely processed and stained. Histological and immunohistochemical investigation for anti-CD18, CD204, CD79a, CD20, CD3, FeLVp27and FeLVgp70 and clonality assessment were performed.

RESULTS

Four male and two female domestic shorthair cats, mean age 11.2 years, developed SPTCL in the abdominal (three), inguinal (two) and thoracic (one) regions. Variably pleomorphic neoplastic lymphoid cells were present in the panniculus in percentages, expanding the septa (six of six) and extending into fat lobules in one of six cats. Tumours were associated with elevated numbers of neutrophils (five of six), lesser macrophages (six of six) and variable necrosis (six of six). Neoplastic cells expressed CD3+ (six of six), with clonal T-cell receptor rearrangement detected in five of six cats.

CONCLUSIONS AND CLINICAL RELEVANCE

This is the first description of SPTCL in cats. Lesions can be confused with panniculitis, leading to delay in diagnosis and therapy. Awareness of this neoplastic disease is relevant to avoid misdiagnoses and to gain greater knowledge about the disease in cats.

Disseminated T-cell lymphoma with non-epitheliotropic cutaneous involvement in a cat with erythematous patches and regenerative anemia

A 14-y-old, castrated male, diabetic, domestic longhaired cat was presented for investigation of anemia. General examination revealed widespread cutaneous erythematous macules and patches. Hematology and bone marrow aspiration revealed severe regenerative anemia and marked erythroid hyperplasia, respectively. Low numbers of intermediate-to-large, atypical lymphocytes were observed in the blood smear and bone marrow aspirates. Various imaging modalities demonstrated a diffuse pulmonary bronchial pattern, multifocal mural thickening of the urinary bladder, splenomegaly, and mild tri-cavitary effusion. Skin biopsies and cytologic examination of the pleural effusion demonstrated round-cell neoplasia consistent with lymphoma. Autopsy confirmed disseminated T-cell lymphoma, mostly affecting the urinary bladder, stomach, lymph nodes, and interscapular subcutis and muscles. Angiocentrism and nerve infiltration were present. The cutaneous erythematous patches, characterized by perivascular neoplastic lymphocytic infiltrates and angiodestruction, were a manifestation of the disseminated lymphoma in this cat, similar to the lesions reported in humans affected by angioimmunoblastic T-cell lymphoma.

Extravascular papillary endothelial hyperplasia mimicking soft tissue sarcoma in 2 cats: a potential diagnostic pitfall

Papillary endothelial hyperplasia (PEH) is a rare soft tissue lesion arising from excessive reactive endothelial cell proliferation described in humans, dogs, and horses. PEH is considered a diagnostic challenge in humans, in which it is frequently misdiagnosed as angiosarcoma. We describe here PEH that developed at injection sites in 2 cats that were initially misdiagnosed as feline injection-site sarcoma by cytology and as subcutaneous angiosarcoma by histopathology. Morphologic features included sharp demarcation from surrounding tissues, and a layered microscopic architecture with an outer fibrous capsule from which emerged fibrovascular stalks covered by a monolayer of factor VIII-related antigen and CD31-positive flat-to-plump endothelial cells. Both lesions had a cystic core containing abundant erythrocytes and fibrin. PEH lesions did not recur in either case. Immunohistochemistry for α-smooth muscle actin and desmin demonstrated that the capsule was devoid of smooth muscle cells, excluding an intravascular origin. PEH in these cats was hypothesized to have developed extravascularly following trauma related to injection. We wish to provide awareness of PEH in domestic cats and of the risk of misdiagnoses leading to overtreatment.

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.

Feline lymphoplasmacytic rhinitis (FLPCR): Severity of inflammation correlates with reduced mucosal IgA expression

Feline lymphoplasmacytic rhinitis (FLPCR) is a rare disease with an unclear pathogenesis characterized by lymphoplasmacytic (LPC) inflammation and progressive tissue destruction. Aims were to evaluate specific FLPCR clinical and pathological features to gain insights into disease pathogenesis. Signalment, clinical signs, serology and 47 pin. h biopsies were retrospectively collected from 33 FLPCR and 3 normal cats. Microscopical lesions and immunohistochemistry results utilizing anti-CD3, anti-CD20, anti-FOXP3, anti-feline-IgA, IgG, IgE and anti-FeLV (p27 and gp70), FIV, FCV and, FHV were scored and most were analyzed statistically. The majority of cats were domestic short haired (26/31) with median age of 11 years and a 0.35 F/M ratio. Serology evidenced 3/22 FIV and 1/22 FeLV positive cats. Immunohistochemistry evidenced 1/33 FeLV-p27 positive cats. Common clinical signs were sneezing (19/24 [79 %]), mucous discharge (13/24 [54 %]) and stertor (10/24 [42 %]). In normal tissues, IgAs were expressed in mucin, apical and lateral cell membrane of columnar cells and in periglandular plasma cells. IgGs were expressed in 20-30 % of columnar cells. Number of clinical signs was statistically significantly higher in female cats (p < 0.0001) and was significantly correlated with chronicity (p = 0.004), and IgG scores (p = 0.01). LPC severity scores correlated positively with infiltration of neutrophils (p = 0.015), gland destruction (p = 0.019) and angiogenesis (p = 0.016) and negatively with fibrosis (p < 0.0001). LPC severity scores were also significantly associated to female sex (p = 0.01) and to IgA (p = 0.03), with higher IgA scores associated to lower LPC scores. FLPCR associated to disruption of mucosal defense mechanisms generating cycles of tissue inflammation, tissue damage and repair with progressive loss of function independent from viral infections.

Multifocal cutaneous non-epitheliotropic B-cell lymphoma in a cat

Case summary

Skin tumours are the second-most common form of feline cancer after haematopoietic neoplasms and are often malignant. Cutaneous lymphoma is uncommon in cats and can be classified as epitheliotropic (typically of T-cell origin) or non-epitheliotropic (either of T-cell or B-cell origin). The present study describes a case of multifocal cutaneous non-epitheliotropic B-cell lymphoma. The skin nodules were multiple and variable in size; showed rapid progression; were alopecic and erythematous in appearance and pruritic and ulcerated; and were mostly located on the trunk. Nodule biopsies revealed the presence of uniform medium-to-large round neoplastic cells that infiltrated the dermis and subcutis. The neoplasias were consistent with a round cell cutaneous tumour and did not show evidence of epitheliotropism. Furthermore, immunohistochemical assessments indicated an immunophenotype characterised by round cells with a strong membrane and cytoplasmic positivity for the CD20 antigen, consistent with a lymphocyte of B-cell origin.

Relevance and novel information

Cutaneous non-epitheliotropic B-cell lymphoma in cats is rare and was previously reported to appear as single dermal and subcutaneous masses that are variable in size and generally develop in the tarsal region. To our knowledge, this is the first report to describe multifocal cutaneous non-epitheliotropic B-cell lymphoma in a cat.

Replication of Small Ruminant Lentiviruses in Aluminum Hydroxide-Induced Granulomas in Sheep: a Potential New Factor for Viral Dissemination

Aluminum (Al)-based salts are widely used adjuvants in ruminants and other species to strengthen the immune response elicited against vaccine antigen(s). However, they can lead to the formation of long-lasting granulomas composed of abundant activated macrophages. Small ruminant lentiviruses (SRLV) are widely distributed macrophage-tropic retroviruses that cause persistent infections in sheep and goats. Infected monocytes/macrophages and dendritic cells establish an inflammatory microenvironment that eventually leads to clinical manifestations. The aim of this work was to study the effect of Al-induced granulomas in the replication and pathogenesis of SRLV. Eleven adult, naturally SRLV-infected sheep showing clinical arthritis were distributed in vaccine (n = 6), adjuvant-only (n = 3), and control (n = 2) groups and inoculated with commercial Al-based vaccines, Al hydroxide adjuvant alone, or phosphate-buffered saline, respectively. In vitro studies demonstrated viral replication in Al-induced granulomas in 5 out of 10 sheep. Immunohistochemistry (IHC) evinced granular, intracytoplasmic SRLV presence in macrophages within granulomas. Viral sequences obtained from granulomas, blood monocytes, and other tissues were highly similar in most animals, suggesting virus circulation among body compartments. However, notable differences between isolated strains in granulomas and other tissues in specific animals were also noted. Interestingly, the B2 subtype was the most commonly found SRLV genotype, reaching a wider body distribution than previously described. Recombination events between genotypes B2 and A3 along the gag region were identified in two sheep. Our results indicate that Al-hydroxide-derived granulomas may represent an ideal compartment for SRLV replication, perhaps altering natural SRLV infection by providing a new, suitable target tissue.IMPORTANCE Granulomas are inflammation-derived structures elicited by foreign bodies or certain infections. Aluminum adjuvants included in vaccines induce granulomas in many species. In sheep, these are persistent and consist of activated macrophages. Small ruminant lentiviruses (SRLV), which are macrophage-tropic lentiviruses, cause a chronic wasting disease affecting animal welfare and production. Here, we studied the occurrence of SRLV in postvaccination granulomas retrieved from naturally infected ewes after vaccination or inoculation with aluminum only. SRLV infection was confirmed in granulomas by identification of viral proteins, genomic fragments, and enzymatic activity. The infecting SRLV strain, previously found exclusively in carpal joints, reached the central nervous system, suggesting that occurrence of SRLV in postvaccination granulomas may broaden tissue tropism. SRLV recombination was detected in inoculated animals, a rare event in sheep lentiviruses. Potentially, virus-host interactions within granulomas may modify viral pathogenesis and lead to more widespread infection.

Anaplastic Large T-Cell Lymphoma in the Intestine of Dogs

Anaplastic large T-cell lymphoma (ALTCL) is a rare subtype of non-Hodgkin T-cell lymphoma that occasionally occurs in the gastrointestinal tract of humans. Enteropathy-associated T-cell lymphoma (EATL) type 1 is the most common type of intestinal lymphoma in dogs, and ALTCL has not previously been reported in the intestinal tract of dogs. Thirteen dogs with intestinal masses diagnosed as intestinal lymphoma with anaplastic morphology were reviewed. Clinical data, including treatment protocols, were available for 11 cases. Immunohistochemistry for CD3, CD20, and CD30 was performed for all cases in addition to PCR for Antigen Receptor Rearrangements (PARR) for assessment of clonality. Eight (62%) of the cases presented with intestinal perforation, and all cases had 1 or more masses arising from the small intestine. Histologically, all cases were characterized by transmural infiltrates of large, CD3-positive and frequently CD30-positive cells. Neoplastic T cells had marked anisocytosis and anisokaryosis, prominent nucleoli, and occasionally indented to reniform nuclei. There was abundant necrosis and inflammation with occasional vascular invasion within neoplastic masses. All cases had a monoclonal T-cell receptor γ gene rearrangement. The median survival time was 5 days, with 1 dog surviving 2 years after the initial diagnosis. ALTCL can occur as an aggressive transmural lymphoma in the gastrointestinal tract of dogs and commonly causes intestinal perforation. ALTCL can be differentiated from EATL type 1 and might have implications for accurate prognostication and selection of therapeutic options in the future.

Cutaneous non-epitheliotropic T-cell lymphoma associated with a fracture site in a cat

Case summary

A 7-year-old male neutered domestic shorthair cat presented for investigation of a swelling over the right forelimb. Radiographs of the right forelimb revealed significant lysis and soft tissue swelling surrounding a previously implanted surgical plate, used to repair a fracture of the distal radius 5 years prior. The implant was removed, and a biopsy was collected. Histopathological analysis and immunohistochemistry diagnosed a non-epitheliotropic T-cell cutaneous lymphoma. Staging confirmed multiple regional lymph node involvement. The cat was started on a CHOP-based protocol (vincristine, doxorubicin, cyclophosphamide and prednisolone). At week 4, the disease progressed both locally and within the regional lymph nodes. The primary lesion became severely ulcerated and the cat was euthanased, 42 days post-diagnosis.

Relevance and novel information

This is the first report of a cutaneous non-epitheliotropic lymphoma developing at the site of a previous traumatic fracture and metal implant. The cat's response to chemotherapy was poor and euthanasia was performed owing to progressive disease. More investigation is required to understand the role that malignant transformation could have at sites of chronic inflammation, bone fractures and surgical implants.

Does categorisation of lymphoma subtypes according to the World Health Organization classification predict clinical outcome in cats?

Objectives The purpose of this study was to specify lymphoma subtypes according to the World Health Organization (WHO) classification in a group of cats and to investigate their potential prognostic value. Methods Records of cats from the University of Veterinary Medicine Vienna suffering from lymphoma were reviewed in this retrospective study. To diagnose various subtypes specified in the WHO classification, histopathological and immunohistochemical examinations, as well as clonality assays in some cases, were performed. Results Of the 30 cats included in this study and classified according to the WHO guidelines, peripheral T-cell lymphoma was the most prevalent lymphoma subtype (37% of cases; n = 11), followed by diffuse large B-cell (23%; n = 7), intestinal T-cell (10%; n = 3), T-cell-rich B-cell (10%; n = 3), large granular lymphocytic (7%; n = 2), anaplastic large T-cell (7%; n = 2), B-cell small lymphocytic (3%; n = 1) and T-cell angiotropic lymphoma (3%; n = 1). The median survival time (MST) was 5.4 months (range 6 days to 2.2 years), with two cats still alive after 1.7 and 2.0 years, respectively. Treating cats prior to chemotherapy with glucocorticoids did not worsen their prognosis. Adding to chemotherapy, radiotherapy or surgery did not improve the clinical outcome. We observed that patients with intestinal T-cell lymphoma lived significantly longer (MST 1.7 years) than those with a diffuse large B-cell (MST 4.5 months) or peripheral T-cell lymphoma (MST 6.1 months). Cats with T-cell-rich B-cell lymphoma survived significantly longer (MST 1.2 years) than those with a diffuse large B-cell lymphoma. Conclusions and relevance A detailed diagnosis of feline lymphoma can be obtained by allocating different subtypes according to the WHO classification. From the eight detected lymphoma subtypes, two, intestinal T-cell lymphoma and T-cell-rich B-cell lymphoma, showed promising survival times in cats.