Veterinary Pathology

Feline mammary carcinoma is highly malignant and generally associated with a poor prognosis, although studies suggest the range of survival times in affected cats is broad. Histologic grading of these tumors is achieved using the Elston and Ellis system, originally developed for human breast cancer. In cats, however, classification using this method has variable prognostic value. Therefore, objectives of this study were (1) to evaluate the Elston and Ellis grading system for feline mammary carcinoma in a predominantly spayed population and (2) to determine whether modification of this system or development of a novel system improved the prognostic value of histologic grading. Survey data and histologic features for 108 carcinomas from 97 cats were analyzed with respect to overall survival. Elston and Ellis grading failed to correlate significantly with overall survival. Using multivariable analysis, lymphovascular invasion, nuclear form, and mitotic count each demonstrated independent prognostic significance (P = .008, <.001, and .004, respectively). Modifications of the Elston and Ellis system and a novel grading system were proposed based on these results; all showed significant correlation with overall survival (P < .001). Median survival times were 27, 29, or 31 months for grade I; 14, 12, or 14 months for grade II; and 13, 5, or 8 months for grade III carcinomas using the mitotic-modified Elston and Ellis, the revised Elston and Ellis, or the novel grading system, respectively. Based on this retrospective study, adoption of the species-specific systems as proposed here may improve the prognostic value of histologic grading for feline mammary carcinoma.

Lymphoma is the most common feline upper respiratory tract (URT) tumor. Primary nasal and nasopharyngeal lymphomas have been evaluated as distinct pathological entities; however, data on their differing clinical behavior are missing. A total of 164 endoscopic- guided URT pinch biopsies were formalin fixed and routinely processed. Imprint cytological specimens were stained with May Grünwald-Giemsa. Immunohistochemistry for anti-CD20, CD3, FeLVp27, and FeLVgp70 was performed. Prognostic significance of clinicopathological variables was investigated by univariate and multivariate analysis. Lymphoma was diagnosed in 39 cats (24%). Most cats with lymphoma were domestic shorthair (32 [82%]), were male (F/M = 0.56), and had a mean age of 10.3 years (range, 1–16 years). Lymphomas were primary nasal in 26 cats (67%), nasopharyngeal in 6 (15%), and in both locations (combined lymphomas) in 7 cats (18%). Neoplastic growth pattern was diffuse in 35 cases (90%) and nodular in 4 (10%). Epitheliotropism was observed in 10 cases (26%). Tumor cells were large in 15 cases, were small and medium in 11 cases each, and 2 had mixed cell size. Submucosal lymphoplasmacytic inflammation was observed in 23 cases (59%). Cytology was diagnostic for lymphoma in 12 of 25 cases (48%). A B-cell origin prevailed (34 [87%]). Feline leukemia virus (FeLV) p27or gp70 antigen was detected in 21 lymphomas (54%). URT lymphomas were aggressive, with survival varying from 0 to 301 days (mean, 53 days). Epitheliotropism in 8 B-cell lymphomas (80%) and in 2 T-cell lymphomas (20%) correlated with prolonged survival. Age younger or older than 10 years had a negative prognostic value. Lymphoplasmacytic inflammation and FeLV infection may represent favoring factors for URT lymphoma development.

The prognostic significance of histologic and clinical features was evaluated in a retrospective study of 70 dogs treated with nephrectomy for renal cell carcinoma. Dogs presenting with hematuria and cachexia had significantly decreased overall and tumor-specific survival. Mitotic index (MI), nuclear size, nuclear pleomorphism, tumor differentiation, invasiveness, Fuhrman nuclear grade, and clear cell morphology were significantly associated with survival times (overall and tumor specific) in univariate analyses. A multivariate Cox proportional hazards model was constructed using stepwise selection to evaluate potential histologic predictor variables. This multivariate analysis revealed MI, defined as the number of mitotic figures in ten 400× fields, as the sole independent prognostic variable. Median survival for dogs with an MI >30 was 187 days compared with 1184 days for dogs with an MI of <10. Dogs with an intermediate MI of 10 to 30 had a median survival of 452 days. Canine renal carcinomas were categorized into the following subtypes based on histologic features and histochemical and immunohistochemical staining: (1) clear cell, (2) chromophobe, (3) papillary, and (4) multilocular cystic renal cell carcinomas. Clear cell carcinoma was diagnosed in 6 of 70 (9%) canine tumors and was associated with a significantly decreased median survival time. Papillary carcinomas were identified in 15 of 70 tumors (21%), chromophobe in 6 of 70 (9%), and the multilocular cystic variant of canine renal cell carcinoma in 3 of 70 tumors (4%). These findings facilitate uniform categorization of canine renal cell carcinoma and provide veterinary pathologists with criteria to determine prognostic information.

Survivin is reexpressed in most human breast cancers, where its expression has been associated with tumor aggressiveness, poor prognosis, and poor response to therapy. Survivin expression was evaluated in 41 malignant canine mammary tumors (CMTs) by immunohistochemistry, in relation to histological grade and stage, and correlated with that of some related molecules (β-catenin, caspase 3, heat shock proteins) to understand their possible role in canine mammary tumorigenesis. An increase in nuclear survivin expression, compared with healthy mammary glands, was observed in CMTs, where nuclear immunolabeling was related to the presence of necrosis. No statistically significant relation was found between the expression of the investigated molecules and the histological grade or stage. The present study may suggest an important involvement of survivin in CMT tumorigenesis. Its overexpression in most of the cases evaluated might suggest that targeting survivin in CMTs may be a valid anticancer therapy.

The development of lesions after infection with Mycobacterium avium subsp paratuberculosis (MAP) was examined in an experimental infection model. Goat kids were orally inoculated 10 times with 10 mg bacterial wet mass of MAP (total dose 2.6 × 10⁸ colony-forming units). Six to 7 inoculated goats and 3 controls were autopsied 3, 6, 9, and 12 months postinoculation (mpi), lesions were documented, and samples were collected for histology, immunohistochemistry (IHC), and bacterial culture. Twenty-five of the 26 inoculated goats did not develop clinical signs. Macroscopic lesions were detected in 3 of the 7 inoculated goats as soon as 3 mpi. Jejunal Peyer’s patches (JPPs) were thickened and had ulcerated surfaces and circumscribed serositis. Characteristic granulomatous infiltrates were seen in all goats in gut-associated lymphoid tissues (GALTs), especially JPPs and lymphoid tissue at the ileocecal valve and in intestinal lymph nodes. Granulomatous intestinal infiltrates not associated with GALT were seen beginning at 6 mpi and with increasing frequency thereafter. Interindividual differences in lesions were most pronounced at 12 mpi, varying from mild focal paucibacillary to severe diffuse multibacillary patterns. Bacterial culture of MAP confirmed the IHC findings but was more sensitive and revealed widespread dissemination at 3 and 12 mpi. Granulomatous arteritis was found in intestinal submucosa of several goats. This may contribute to the spreading of MAP to the intestinal wall and possibly systemically. The different lesions observed during the clinically inapparent period of paratuberculosis are most likely indicators for the later progression of infection and development of clinical disease.

Thymic epithelial cells could play an important role in lymphoid depletion during bovine viral diarrhea virus (BVDV) infection. To evaluate this hypothesis, we examined proliferation of lymphocytes, expression of cytokeratins by thymic epithelial cells, and ultrastructural features at sequential time points after experimental infection of colostrum-deprived calves with the noncytopathogenic BVDV1 strain 7443. Ten clinically healthy Friesian calves were used. Eight were inoculated with the virus, and 2 were used as uninfected controls. Calves were sedated and euthanized in batches between 3 and 14 days postinoculation. At necropsy, thymus samples were collected for structural, immunohistochemical, and ultrastructural study. Thymic lymphoid depletion was accompanied by a decrease in lymphocyte proliferation and immunohistochemical and ultrastructural changes in thymic epithelial cells. Immunohistochemical and ultrastructural results reflect a disturbance of the thymic epithelial cell network, which may explain the decrease in lymphocyte proliferation by defective thymocyte-epithelial cell interactions.

The formation of biofilms on surgical implants is thought to play a major role in chronic infection and wound-healing disorders and has been rarely described in veterinary medicine. Due to poor and unreliable results from bacterial culturing, histology may be an economic tool for the detection of biofilms. In this study, the prevalence of biofilms on surgical suture materials and swabs with chronic wound-healing complications in dogs, cats, and horses was assessed by histologic examination using hematoxylin and eosin, Gram, and Giemsa stains, as well as periodic acid–Schiff reaction. Of the 91 tissue samples with intralesional suture material or swab residues associated with inflammation, only 2 contained bacterial colonies arranged in an extracellular polymeric matrix consistent with a biofilm. The results of this study suggest that biofilms on suture material may occur in veterinary medicine.

In veterinary medicine, anemia without an appropriate compensatory hematopoietic response is termed nonregenerative. Nonregenerative anemia is a common clinical entity, occurring as a result of diminished or ineffective erythropoiesis in association with many types of pathology. This article reviews nonregenerative anemia in domestic animals, emphasizing mechanisms of disease, and also covers other conditions associated with nonregenerative anemia in people. Many aspects of nonregenerative anemia in animals are worthy of further investigation, from molecular mechanisms of disease to epidemiologic impacts.

Coagulation factor XII (FXII) may be important in cardiovascular and inflammatory diseases. We have identified and characterized a naturally occurring mutation in the feline FXII gene that results in a mutant protein and enzymatic loss of activity. Feline intron/exon gene structure and sequence were acquired by comparing DNA sequences obtained from a fragmented Felis catus genomic sequence and the National Center for Biotechnology Information’s Cross Species Megablast of multiple species’ FXII gene sequences. Fourteen exons ranging in size from 57 to 222 base pairs were confirmed spanning 8 Kb on chromosome A1. The 1828–base pair feline FXII messenger RNA (mRNA) sequence contains an open reading frame that encodes a protein of 609 amino acids with high homology to human FXII protein. Total RNA and mRNA purified from liver tissue of 4 wild-type/normal and 8 FXII-deficient cats confirmed the predicted mRNA sequence and identified one important single-nucleotide polymorphism (SNP). A single base deletion in exon 11 of the FXII coding gene in our colony of cats results in deficient FXII activity. Translation of the mRNA transcript shows a frame shift at L441 (C441fsX119) resulting in a nonsense mutation and a premature stop codon with a predicted 560–amino acid protein. The mutant FXII protein is truncated in the 3′ proteolytic light chain region of the C-terminus, explaining its loss of enzymatic activity. This study is the first molecular characterization of the feline FXII gene and the first identification of an FXII mutation in the domestic cat, providing insights into the origin and nature of feline FXII deficiency.

Canine toxic epidermal necrosis (TEN), a rare and life-threatening cutaneous drug reaction, traditionally has been described as full-thickness devitalization of the epidermis with minimal dermal inflammation; however, few reports detail the histologic findings. We characterize the clinical features and histologic variations of 3 canine TEN patients. Clinically, irregular erythematous and purpuric macules evolved into widespread and severely painful erosions. The number of eroded mucosae varied; however, periocular and perilabial mucocutaneous junctions frequently were affected. Thirteen of 17 biopsies were evaluated. Apoptosis at multiple epidermal levels was the most common pattern of epidermal necrosis (12/13 biopsies, 92%). In contrast, full-thickness coagulation necrosis was present less often (7/13 biopsies, 52%). Lymphocytic interface dermatitis was the predominant inflammatory pattern, and intraepidermal lymphocytes, along with fewer histiocytes, were present to some degree in all samples along with lymphocytic satellitosis of apoptotic keratinocytes. The sequence of changes points to lymphocyte-mediated keratinocyte apoptosis as an early step in lesion development with subsequent variation in progression to coagulation necrosis among patients. Histopathologic changes overlapped with those reported for erythema multiforme, in contrast to traditional histologic descriptions of canine TEN. A specific algorithm for assessment of drug causality in epidermal necrolysis (ALDEN) was applied for each patient; carprofen was associated with a probable score for causality in 1 dog. Clinicians should be encouraged to take multiple biopsies in TEN suspect cases as nearly 25% of all biopsies lacked epithelium and were not diagnostic.

A novel form of primary feline hemangiosarcoma and additional cases of plexiform vascularization in the cervical lymph nodes are reported. Sixteen cases of feline lymphadenopathy attributed to abnormal vascular proliferation were identified and evaluated. Most of these lesions were diagnosed histologically as hemangiosarcoma. However, lesions of plexiform vascularization, with and without areas of putative malignant transformation, were also identified. Mean age of the cats was 11 years (range, 3–16 years) with most being domestic shorthair and medium hair (13). Two domestic long hair and 1 Maine Coon were identified. Excisional nodal biopsy was performed in 15 cases and incisional biopsy in 1 case. Six cats were euthanized due to their disease. Survival times ranged from ≤1 month to ≥30 months. We provide a new clinical differential for cervical lymphadenopathy in cats that is not widely recognized. Proper identification of primary nodal vascular lesions in cats will enable further characterization of clinical features and biologic behavior to determine specific therapy.

Pheochromocytoma-associated catecholamine-induced cardiomyopathy is a well-known entity in man, nonhuman primates, and mice but has not been described in dogs. In this retrospective study, 9 dogs were identified with pheochromocytomas and concurrent cardiovascular pathology observed histologically (n = 6), echocardiographically (n = 4), and/or electrocardiographically (n = 5). Cardiac lesions included multifocal cardiomyocyte necrosis with contraction bands, cardiomyocyte degeneration, myocardial hemorrhage, lymphohistiocytic myocarditis, and interstitial fibrosis. Clinical procedures, including electrocardiographic and echocardiographic examinations, Doppler blood pressure measurement, and auscultation, were available for 5 dogs and consistently revealed concentric or mixed (eccentric and concentric) ventricular hypertrophy. Additional changes observed included arrhythmias, systemic hypertension, and heart murmurs. The myocardial lesions observed in this series of dogs are similar to those observed in humans with pheochromocytoma-associated catecholamine-induced cardiomyopathy. Since the clinical manifestations of catecholamine-induced cardiac disease are amenable to medical treatment, recognition of this cardiomyopathy has the potential to reduce morbidity and mortality in dogs with pheochromocytoma.

A diffuse, chronic, superficial neocortical degeneration that resulted in atrophy was detected in five 1 to 2-year-old-dogs. Presenting neurologic signs included ataxia, dysphagia, blindness, and mentation changes. Magnetic resonance imaging on brains from 2 dogs demonstrated severe bilateral cerebrocortical atrophy and enlarged lateral and third ventricles. Grossly, multifocal, bilaterally symmetrical, extensive areas of neocortical brownish discoloration associated with atrophy of gyri and sulcal widening were recorded in the dorsal and lateral cerebral hemispheres in 3 dogs. Microscopically, in all dogs there was subacute to chronic superficial neocortical degeneration affecting all cerebral lobes, ranging from loss of the molecular layer to less frequent larger and deeper cavitations of variable size. Clinical signs probably resulted from a combination of primary neocortical degeneration and secondary degeneration in the corticobulbar and corticospinal tracts. The distribution pattern of gross and histologic cerebrocortical lesions suggests that this is a novel degenerative canine cerebral disease.

Cutaneous mucinosis is a cutaneous disorder described in humans, dogs, and rarely cats but never reported in birds. Twenty-six brown egg–laying chickens between ages 43 and 46 weeks had a history of feather loss, scaly, dry skin, weight loss, and decreased egg production. Microscopic findings in the skin included fragmentation of collagen bundles and interstitial, periadnexal, and perivascular dermal accumulation of wispy, mildly basophilic material that was also occasionally observed within the follicular epithelium. A moderate lymphoplasmacytic and heterophilic perivascular dermatitis was also observed. The wispy to granular material was diffusely Alcian blue positive and periodic acid–Schiff negative (consistent with mucin), suggesting a diagnosis of primary or secondary cutaneous mucinosis. The cause of this condition could not be determined.

A 1-year old female spayed German Shepherd dog was evaluated for acute onset of dyspnea. Pyogranulomatous inflammation and green globoid structures were present on aspirates of the affected lung. Impression smears and histopathology confirmed pyogranulomatous pneumonia, with large amounts of lipid corresponding to the green structures noted cytologically, and identified poorly staining bacterial rods within lipid vacuoles. Special stains confirmed the presence of acid-fast bacterial rods, and polymerase chain reaction and DNA sequencing identified the organism as Mycobacterium fortuitum. M. fortuitum pneumonia is well described in humans and has previously been reported in 4 dogs and 1 cat. Lipid was a prominent cytologic and histologic feature, as is often described in humans and in the single feline case report. Additionally, this case highlights the variable cytologic appearance of lipid, as well as Mycobacterium spp, which are classically nonstaining with Wright-Giemsa.

The placenta from an embryo transfer–recipient mare and live foal was examined. The placenta was effaced by multifocal masses, which ranged from less than 1 cm to 14 cm in diameter. The foal represented at 52 days for lethargy, ataxia, and urine dribbling; due to a poor prognosis, the foal was euthanized. At necropsy, the liver was effaced by multifocal, pale, irregular nodules. The lumbar vertebrae and other skeletal sites had multifocal lytic lesions. The placenta had 4 populations of neoplastic cells, including a spindle cell population, tall columnar and transitional epithelial cell populations, and an undifferentiated polygonal cell population. The foal’s liver had similar populations and patterns of cells as those in the placenta. The lesion in the placenta and the masses in the foal were diagnosed as a mixed germ cell tumor and metastatic mixed germ cell tumor, respectively.

Intravascular nematodes were considered the cause of death of 14 captive callitrichids. All animals were captive born at zoos in France and died with little or no premonitory signs of disease. No consistent gross lesions were observed at necropsy, although in certain cases intracardiac adult parasites were noted. The most significant histologic findings were verminous pneumonia and pulmonary endarteritis. In all cases except one, intravascular adult nematodes were observed with eggs and larvae in the lungs. Adult nematodes were obtained from 8 animals and in all cases were identified as Parastrongylus dujardini. To the authors’ knowledge, this is the first report of intravascular angiostrongylosis with primary cardiopulmonary location in callitrichids in France.

Hepatic lesions in nondomestic felids are poorly characterized. The purpose of this study was to evaluate hepatic lesions in 90 captive, nondomestic felids including tigers, cougars, and lions. Hepatic lesions were histologically characterized as vacuolar change (lipidosis or glycogenosis), biliary cysts, biliary hyperplasia, hepatitis, necrosis, neoplasia, fibrosis, veno-occlusive disease, cholestasis, hematoma, congestion, or hemorrhage. Stepwise logistic regression analyses were performed for vacuolar change, benign biliary lesions, hepatitis, lipogranulomas, extramedullary hematopoiesis, and hepatic stellate cell hypertrophy and hyperplasia, with species as the outcome variable. Ninety cats met the inclusion criteria. Seventy livers (78%) contained 1 or more lesions. Hepatocellular vacuolar change (41/90 [46%]) was the most common lesion overall. Extramedullary hematopoiesis, lipogranulomas, and hepatic stellate cell hyperplasia were also common. One snow leopard had veno-occlusive disease. Tigers were more likely than other felids to have no significant hepatic histologic lesions (odds ratio [OR], 12.687; P = .002), and lions were more likely to have biliary cysts (OR, 5.97; P = .021). Six animals (7%) died of hepatic disease: cholangiocellular carcinoma (n = 2) and 1 each of hepatic lipidosis, hepatocellular necrosis, pyogranulomatous hepatitis, and suppurative cholecystitis. Hepatocellular iron and copper accumulations were present in 72 of 90 (80%) and 10 of 90 (11%) sections, respectively. Sinusoidal fibrosis was common (74/90 [82%]) and primarily centrilobular (65/74 [88%]). Hepatocellular iron, copper, and fibrosis were not significantly associated with hepatic lesions. Primary hepatic disease was not a common cause of death in nondomestic felids in this study.

Mucoperiosteal exostoses (MpEs) of the tympanic bulla (TB), also referred as middle-ear otoliths, have been occasionally described in dogs and cats in association with clinical signs of otitis media or as an incidental finding, but they have not been recorded in other species. In this report, we describe the radiographic, gross, and histopathologic features of MpEs in 8 African lions (Panthera leo). All animals (5 males and 3 females) were adults that had been kept in captivity and had their skeletons conserved as part of an anatomic academic collection. A radiographic study revealed mineralized structures in the TB consistent with MpEs in 7 of the 16 examined TB; a computed tomography study identified MpEs in 12 of the 16 TB. Six TB from 4 lions were sectioned, and several MpEs were demineralized for histopathologic analysis. Grossly, MpEs appeared variable in number and shape. Some were globular structures that were loosely attached to the mucosal surface of the TB; others were isolated to coalescent bone spicules extending from the mucoperiosteum. Position was also variable, but MpEs frequently developed in the hypotympanum, especially on the ventromedial aspect of the TB wall. Microscopically, MpEs were composed of osteonal bone growing from the periosteum and not by dystrophic calcification of necrotic tissue debris, as is hypothesized in dogs.

Amphibians in the family Ranidae (true frogs) seem highly susceptible to oxalosis, particularly when fed a diet high in oxalic acid during the premetamorphic (tadpole) stage. The authors describe the mortality of 150 captive-raised wood frogs (Rana sylvatica or Lithobates sylvaticus) from oxalate nephrolithiasis and renal tubular necrosis caused by consumption of boiled spinach during tadpole development. Renal lesions were due to intraluminal transparent crystals which were birefringent under polarized light and were identified morphologically and histochemically as composed of calcium oxalate. Evidence of early fibrosis or squamous metaplasia, and a presentation at least 2 weeks after spinach consumption had ended, suggested a subacute course. Tadpole-feeding protocols should avoid plants with high oxalate content (eg, spinach and rhubarb leaves), and any episode of high mortality in captive amphibians along with nephrolithiasis should prompt an evaluation of the feed sources for material with high oxalate content.

Chordomas are uncommon neoplasms arising from notochord remnants, most commonly occurring in the axial skeleton. Extraskeletal soft tissue chordomas are rare primary tumors, and primary alimentary tract chordomas have not been reported. Herein we report 24 cases of spontaneous primary intestinal chordomas in zebrafish, as well as 9 spontaneous vertebral chordomas. Both intestinal and vertebral tumors showed invasive behavior, although more commonly in the latter. In all cases of primary intestinal chordomas, there was no axial or peripheral skeletal or other nonvisceral involvement. Although uncommon, intestinal chordomas represent a unique background lesion in aged zebrafish.

This report describes atypical cases of yersiniosis in squirrel monkeys in which aberrant forms of Yersinia pseudotuberculosis were seen. There were 2 outbreaks due to yersiniosis in squirrel monkeys in Japan. The monkeys had systemic necrotizing and hemorrhagic lesions with Gram-negative rod-shaped bacilli and microthromboembolism in the kidneys. Some lesions contained filaments, globular bodies, and other pleomorphic forms of bacteria. All forms were usually seen in the same lesions, and those with pleomorphic morphology appeared to be an intermediate form between the rod-shaped bacteria and the filaments or globular bodies. In addition, they had strong immunolabeling for Y. pseudotuberculosis, as did the rod-shaped bacteria. Therefore, the globular bodies, filaments, and others are strongly suspected to be shape-changed bacilli of Y. pseudotuberculosis. These morphologically altered bacteria could cause errors in diagnosis since they resemble fungi or protozoa, and special staining techniques, including immunohistochemistry, can be helpful in establishing the correct diagnosis.

Cytochrome P450 1B1 (CYP1B1) is highly expressed in human and murine ocular tissues during development. Mutations in this gene are implicated in the development of primary congenital glaucoma (PCG) in humans. Mice deficient in Cyp1b1 (Cyp1b1^–/– ) present developmental abnormalities similar to human primary congenital glaucoma. The present work describes the ultrastructural morphology of the iridocorneal angle of 21 eyes from 1-week-old to 8-month-old Cyp1b1^–/– mice. Morphometric and semiquantitative analysis of the data revealed that 3-week-old Cyp1b1^–/– mice present a significantly (P < .005) decreased amount of trabecular meshwork (TM) collagen and higher TM endothelial cell and collagen lesion scores (P < .005) than age-matched controls. Collagen loss and lesion scores were progressively increased in older animals, with 8-month-old animals presenting severe atrophy of the TM. Our findings advance the understanding of the effects of CYP1B1 mutations in TM development and primary congenital glaucoma, as well as suggest a link between TM morphologic alterations and increased intraocular pressure.

Nonalcoholic fatty liver disease (NAFLD) is considered the hepatic manifestation of metabolic syndrome. The more clinically concerning form of the disease, nonalcoholic steatohepatitis (NASH), is characterized by steatosis, lobular inflammation, and ballooning degeneration. Here we describe a naturally occurring syndrome in the common marmoset that recapitulates the pathologic findings associated with NAFLD/NASH in humans. Hepatomegaly determined to result from NAFLD was observed in 33 of 183 marmosets. A comprehensive histopathologic assessment performed in 31 marmosets demonstrated that NAFLD was characterized by variably sized, Oil Red O staining cytoplasmic vacuoles and observed primarily in animals with evidence of obesity and insulin resistance. A subset of marmosets (16 of 31) also demonstrated evidence of NASH characterized by multifocal inflammation combined with ballooning hepatocellular degeneration. Marmosets with NASH demonstrated an increase in immunostaining with an antibody targeted against the human leukocyte antigens (HLA)–DP, HLA-DQ, and HLA-DR compared with marmosets without NASH (38.89 cells/10× field vs 12.05 cells/10× field, P = .05). In addition, marmosets with NASH demonstrated increased Ki-67 immunopositive cellular proliferation compared with those without (5.95 cells/10× field vs 1.53 cells/10× field, P = .0002). Finally, animals with NASH demonstrated significantly increased mean circulating serum iron levels (160.47 μg/dl, P = .008) and an increase in numbers of Prussian blue–positive Kupffer cells (9.28 cells/40× field, P = .005) relative to marmosets without NASH (97.75 μg/dl and 1.87 cells/40×, respectively). This study further characterizes the histopathology of NAFLD/NASH and suggests that the marmoset may be a valuable animal model with which to investigate the host and environmental factors contributing to the progression of NAFLD/ NASH.

Macrophages are an important leukocyte component of the microenvironment of neoplasms. Macrophages have classically been subdivided into M1 and M2, depending on their roles in immune response, wound healing, and promotion or inhibition of tumor growth. In human breast cancer, increased presence of M2 macrophages has been associated with poor prognosis. The authors hypothesized that rat mammary carcinomas have increased macrophage influx compared to benign mammary proliferative lesions and normal mammary glands as well. In humans, both M1 and M2 macrophages express CD68, while CD163 is expressed primarily by M2 macrophages. Based on a single immunolabeling protocol with anti-CD68 and anti-CD163 antibodies, the extent of macrophage influx was investigated by morphometry to quantitate the immunopositive cells in normal rat mammary glands, benign mammary proliferative lesions, and mammary carcinomas. In mammary carcinomas, there was significantly higher percentage of CD68+ cells compared to benign mammary proliferative lesions and normal mammary glands. There was also higher percentage of CD163+ cells in mammary carcinomas compared to benign mammary proliferative lesions. Thus, increase in CD68+ and CD163+ macrophages corresponded to increased malignancy of rat mammary tumors in this study.

Biopharmaceuticals, produced by recombinant DNA technology, are generally more complicated to produce than small molecule drugs. As patents around the development and manufacturing of these biopharmaceuticals expire, biosimilars are being developed as comparable and more affordable alternatives to improve patient access and market competition. This commentary explains what a biosimilar is; it compares and contrasts biosimilar production with that of small molecule, generic, and other biological drugs; and it describes basic principles of the nonclinical development program for monoclonal antibody biosimilars.