Proposal of a 2-tier histologic grading system for canine cutaneous mast cell tumors to more accurately predict biological behavior.

Currently, prognostic and therapeutic determinations for canine cutaneous mast cell tumors (MCTs) are primarily based on histologic grade. However, the use of different grading systems by veterinary pathologists and institutional modifications make the prognostic value of histologic grading highly questionable. To evaluate the consistency of microscopic grading among veterinary pathologists and the prognostic significance of the Patnaik grading system, 95 cutaneous MCTs from 95 dogs were graded in a blinded study by 28 veterinary pathologists from 16 institutions. Concordance among veterinary pathologists was 75% for the diagnosis of grade 3 MCTs and less than 64% for the diagnosis of grade 1 and 2 MCTs. To improve concordance among pathologists and to provide better prognostic significance, a 2-tier histologic grading system was devised. The diagnosis of high-grade MCTs is based on the presence of any one of the following criteria: at least 7 mitotic figures in 10 high-power fields (hpf); at least 3 multinucleated (3 or more nuclei) cells in 10 hpf; at least 3 bizarre nuclei in 10 hpf; karyomegaly (ie, nuclear diameters of at least 10% of neoplastic cells vary by at least two-fold). Fields with the highest mitotic activity or with the highest degree of anisokaryosis were selected to assess the different parameters. According to the novel grading system, high-grade MCTs were significantly associated with shorter time to metastasis or new tumor development, and with shorter survival time. The median survival time was less than 4 months for high-grade MCTs but more than 2 years for low-grade MCTs.

Mast cells and canine mast cell tumours. A review.

This article reviews the literature on mast cells and tumours derived from mast cells in the dog. Mast cells play a central role in inflammatory and immune reactions. Mast cells, normal and neoplastic, contain and release important biologically active substances: heparin, histamine, eosinophilic chemotactic factor and proteolytic enzymes. Mast cell tumours occur in the dog, particularly in the boxer and related breeds, in the skin and less frequently in the intestines. Cytology usually provides an accurate diagnosis, but histological examination adds further information concerning the histologic grade and the completeness of surgical therapy. Cutaneous mast cell tumours should be regarded as potentially malignant and therefore be removed widely (3 cm. margin). Local recurrence, regional and distant metastases together with paraneoplastic disorders may cause the death of the pet. Histologic grading (2 or 3 grades) and clinical staging together with kinetic parameters and breed (boxers have relatively benign tumours) are important prognostic parameters. Based on prognostic criteria, surgical treatment should be completed with adjuvant radiotherapy, corticosteroids and eventually with combined chemotherapy. A novel, promising therapy is the application of the receptor kinase inhibitor. The study of the pathogenesis of mast cell tumours received new impetus by the finding of mutations, deletions and duplications, in exons 11 and 12 of the C-kit oncogene. Further study of physiological and oncological aspects of mast cells are favoured by the availability of mast cells isolated from spontaneous mast cell tumours and of cultured cell lines.

Congenital tumours and tumour-like lesions in domestic animals. 3. Horses. A review.

The literature on congenital tumours and tumour-like lesions in horses was reviewed. Included were embryonic tumours and teratomas. Special attention was paid to the ubiquitous adenomatous hyperplasia of the placenta. It appears that temporal teratomas, interstitial hamartomas and placental adenomatous hyperplasia are unique in the horse. Benign teratoma of the undescended testis is far more frequent in the horse than in other species. In horses, as in calves and pigs, congenital skin tumours were of papillomatous, vascular and melanocytic types. The sporadic occurrence of congenital tumours in the horse did not provide an etiologic or pathogenetic clue. The possibility of oncogenic viruses in cases of congenital skin papilloma or malignant lymphoma could neither be proven, nor be excluded. Hereditary tumours were not encountered.

Congenital and hereditary tumours in domestic animals. 2. pigs. A review.

The literature on congenital and hereditary tumours in pigs was reviewed. One hitherto unreported own case was added. Sporadic cases of congenital tumours included several types found in newborn piglets. Embryonic tumours (nephroblastoma, rhabdomyosarcoma) occurred either in newborn or in juvenile animals. Cardiac rhabdomyomas were provisionally classified as hamartomas. The hereditary tumours, melanomas and lymphomas, were reproducible by experimental matings. These tumours are particularly interesting as models to elucidate genetic and immunologic mechanisms of tumour diseases. Striking is the high degree of regression in porcine melanomas and the associated melanosis.

Tumours in calves: comparative aspects.

In this paper, calf neoplasia is discussed in relation to a series of cases comprising (1). spontaneous congenital bovine tumours of fetuses and newborn animals, (2). spontaneous juvenile-type tumours in calves aged 2-12 months, and (3). iatrogenic tumours of calves. The congenital cases (n=14) consisted of tumours of a predominantly mesenchymal and malignant nature (malignant lymphoma, mesothelioma and mixed mesodermal tumour). In the juvenile cases (n=11), malignant lymphoma and sarcoma were the commonest forms. In comparing tumour patterns in calves with those reported in adult cattle, it was apparent that tumours were less common in the former (6 versus 60 per 100000) and that, with the exception of malignant lymphoma, the types of tumour differed. Carcinomas, which were virtually absent in calves, predominated in adults, probably due to the longer exposure of older animals to carcinogenic factors. In comparing tumour patterns in calves with those reported in pigs and children, it was clear that calf cases were mainly sporadic, with the notable exception of malignant lymphoma in twins. In young pigs, however, several types of tumour (some hereditary) were reported on a single farm as multiple cases. In children, tumours occurred more frequently than in calves, and many neoplasms in both children and calves could be regarded as embryonic tumours or hamartomas. Little is known about the pathogenetic pathways of tumours in calves, with the exception of congenital neuro-fibromatosis (hereditary) and possibly of mesotheliomatosis (due to asbestos). Modern methods of analysing chromosomal and gene aberrations may be helpful in clarifying the pathogenesis of congenital tumours.

Progesterone receptors in normal, dysplastic and tumourous feline mammary glands. Comparison with oestrogen receptors status.

The aims of the study were to standardise an immunohistochemical (IHC) method for the detection of progesterone receptors (PR) on formalin-fixed, paraffin wax-embedded tissue sections of feline mammary gland tumours and dysplasias, comparing the results with those obtained using the radiolabelled ligand dextran coated charcoal (DCC) assay applied to frozen tissue samples from the same cases. Also, to define the immunohistochemical distribution of PR in the different cellular compartments of the lesions and to compare the oestrogen receptor (ER) and PR status of the feline mammary lesions. Proliferative mammary lesions collected from 34 cats were studied; 25 malignant tumours and 9 benign tumours and dysplasias. PR protein was present at a concentration of 5 fmol mg(-1) (positivity threshold) in 37.5 per cent of malignant tumours and 66.7 per cent of benign tumours and dysplasias while immunoreative products to PR antibody were found in the nuclei of tumour cells in 38.5 per cent and 66.7 per cent of the cases, respectively. Concordance between DCC-PR and IHC-PR was 88.5 per cent (P<0.001). The specificity (true negatives) and sensitivity (true positives) of the IHC method were 89.4 per cent and 87.5 per cent respectively. The presence of PR was linked to the absence of ovariectomy (P<0.02). Oestrogen receptors, detected by either method, were also detected in half the cases in which PR had been detected. In malignant tumours, the most prevalent groups were the ER + PR + and ER-PR + groups.

Congenital tumours and tumour-like lesions in domestic animals. 1. Cattle. A review.

The literature on congenital tumours and tumour-like lesions in calves was reviewed. Lesions were subdivided by their anatomical distribution and in addition also according to their histologic-pathogenetic nature. As a result of the latter method, four main groups were formed covering most of the lesions described so far: malignant lymphomas, mesotheliomas, hamartomas and embryonic tumours. Most lesions were of mesenchymal structure, carcinomas being extremely rare. Some findings may point to early genetic events, for instance twin calves both affected with malignant lymphoma and related calves with congenital facial neurofibromatosis. An external factor, asbestos, is suspected to play a role in the genesis of peritoneal mesotheliomatosis. The effects of congenital tumours on their hosts were often considerable: death by generalization (malignant lymphomas), ascites (mesotheliomas) or the growth of large abdominal tumours (nephroblastomas, mixed tumours). The latter two conditions often caused dystocia.

Immunohistochemical analysis of estrogen receptors in feline mammary gland benign and malignant lesions: comparison with biochemical assay.

Estrogen receptors (ER) were determined by both the biochemical dextran-coated charcoal (DCC-ER) and the immunohistochemical Avidin biotin-peroxidase complex (IHC-ER) methods in proliferative mammary lesions collected from 37 cats: 20 malignant tumors without metastasis at first presentation, seven malignant tumors with lung and/or lymph node metastases and 10 benign tumors and dysplasias. Total number of samples analyzed by both methods was 44. The DCC-ER method was applied to frozen tissue samples and the IHC-ER method was applied to neutral buffered formalin-fixed, paraffin wax-embedded tissue samples by using the NCL-6F11 monoclonal antibody. Biochemically, 21 (47.7%) cases had equal or more than 5 fmol/mg of protein (standard positivity threshold). Immunohistochemically, 11 (25%) cases were scored positive, the percentage of positive nuclei being statistically linked to the intensity of immunostaining. Normal mammary gland tissue (13 cases) and/or dysplastic areas (5 cases) found in the surroundings of the main lesion were IHC-ER positive in 76.9% and 40% of the cases, respectively. Concordance between DCC-ER and IHC-DCC was 72.7% and the results of the DCC and the IHC-ER methods were significantly correlated (P < 0.05) by the chi2 test. Specificity (true negatives) and sensitivity (true positives) of the ICH-ER method were 95.6% and 47.6%, respectively. One out of eleven DCC-ER positive and IHC-ER negative discordant cases (9.09%) was a DCC-ER false positive, because the surrounding normal mammary gland tissue was IHC-ER positive. The remaining 10 cases had ER content values equal or lower than 23 fmol/mg of protein, a figure that could represent the sensitivity threshold of the immunohistochemical method employed.

Tyrosinase gene expression in clear cell sarcoma indicates a melanocytic origin: insight from the first reported canine case.

The aim of this study was to characterize a metastasizing soft tissue tumor in a dog, which clinically, grossly and histologically showed a close resemblance to human clear cell sarcoma, a soft tissue variant of malignant melanoma. Ultrastructurally, melanosomes were found, indicating a melanocytic origin of the tumor. Using reverse-transcription polymerase chain reaction, expression of the gene encoding tyrosinase was determined in tumor cells. With this first case of canine clear cell sarcoma, as well as the earlier report from our laboratory on amelanotic melanomas in the cat, we demonstrate that expression of the tyrosinase gene may occur in a broader range of less differentiated melanocytic tumors in different species, including man.

Genomic organization of the canine p53 gene and its mutational status in canine mammary neoplasia.

To determine whether canine malignancies share common genetic lesions with their human counterparts, and are thus potentially interesting model systems in which to pose questions regarding tumor etiology and progression, we have elucidated the entire exon/intron structure of the canine p53 gene. A search for p53 gene abnormalities in mammary tumor tissue was undertaken utilizing single strand conformation polymorphism analysis. Mutations were detected in exons 4, 5, 6, and 7 of the p53 gene and consisted of nonsense, splicing, and frameshift mutations. None of 11 benign tumors and 6 of 40 primary carcinomas (15%) were found to harbor subtle p53 mutations. In 14 carcinomas examined the results in primary tumors and metastases were the same. These findings implicate involvement of this gene in the genesis of some malignant canine tumors, in a fashion similar to their human counterparts.

Liposome-encapsulated muramyl tripeptide phosphatidylethanolamine (L-MTP-PE): a randomized clinical trial in dogs with mammary carcinoma.

In this prospective randomized double-blind clinical study the anti-tumour activity of liposome-encapsulated muramyl tripeptide phosphatidylethanolamine (L-MTP-PE) was evaluated as an adjuvant immunotherapy in dogs with mammary tumours of the simple carcinoma type. Dogs were randomized after surgery to one of two treatment groups, in which they were treated with either L-MTP-PE (2 mg/m2 i.v.; Ciba Geigy Basel, Switzerland) twice weekly for eight weeks, or with empty liposomes according to the same protocol. The minimal follow-up period was one year. Thirteen dogs were entered in the L-MTP-PE group and fourteen dogs in the placebo control group. Only minor toxicities (fever and shivering during 10-24 hours) were seen in six dogs treated with L-MTP-PE, these being mainly of the smaller breeds. At the time of evaluation seven dogs were still disease free. In the other twenty dogs the disease-free period (DFP) was ended by local recurrences in 16 and by distant metastases in 4. The difference in DFP between dogs treated with L-MTP-PE (median 165 days, range 15-905) and dogs in the placebo group (median 133 days, range 27-659) was not significant. The difference in overall survival between the dogs treated with L-MTP-PE (median 222 days, range 36-905) and those receiving the placebo (median 182 days, range 54-659) was also not significant. It was concluded that liposome-encapsulated MTP-PE was not efficacious in the treatment of dogs with mammary carcinoma.

Expression of growth hormone in canine mammary tissue and mammary tumors. Evidence for a potential autocrine/paracrine stimulatory loop.

The role of progestins in the pathogenesis of breast cancer in women remains controversial. To advance this discussion, we report the demonstration and localization of progestin-induced biosynthesis of growth hormone (GH) in canine mammary gland tissue. Nontumorous mammary tissues and tumors, both benign and malignant, were obtained from private household dogs. Immunoreactive GH was localized in mammary epithelial cells and correlated with the presence of GH mRNA. Local synthesis of GH was also proven immunoelectron microscopically by demonstrating GH-containing secretory granules. Cellular GH production in nontumorous tissues was more extensive during the progesterone-dominated luteal phase of the ovarian cycle or during exposure to synthetic progestins than during anestrus. GH was also associated with areas of hyperplastic mammary epithelium, which may indicate that locally produced GH enhances proliferation, acting in an autocrine and/or paracrine manner. In 41 of 44 tumors, GH was present. Of 3 GH-negative tumor samples, 2 were from progestin-depleted, castrated bitches. In nonmalignant mammary tissues, GH production is stimulated by progesterone and synthetic progestins interacting with progesterone receptors. In some progesterone-receptor-negative malignant tumors, GH expression was found, indicating loss of this control. Progestin-induced GH probably participates in the cyclic development of the mammary gland but may promote mammary tumorigenesis by stimulating proliferation of susceptible, and sometimes transformed, mammary epithelial cells.

P53 gene mutations in osteosarcomas in the dog.

Osteosarcomas in 18 dogs were examined for the presence of p53 mutations in exons 4-8 by single strand conformation polymorphism (SSCP) analysis, followed by sequence analysis in tumors demonstrating abnormal bands in the SSCP analysis. P53 mutations were found in four of the primary tumors in 17 dogs. Metastases studied in two of these dogs in which the primary tumor contained only wild type p53 did not contain mutations, nor those of one dog in which the primary tumor was not studied. The alterations that were found included three missense mutations and one 3 bp insertion.

Veterinary cancer epidemiology.

This paper reviews the impact of veterinary cancer epidemiology on veterinary oncology, human oncology, comparative oncology, and on the etiology and pathogenesis of cancer. The detection of clusters of diseased animals has led to the discovery of the infectious, viral-associated nature of malignant lymphoma of cats, poultry, and cattle. Although some viruses (FeLV, BLV) can, under experimental conditions, cross the species barrier, there is thus far no evidence for a zoonotic hazard for the human. The keeping of pet/birds or pigeons was found to be associated with an increased risk of lung cancer in the bird keepers. Dogs appear to be useful 'sentinels' for environmental hazards (asbestos, dyes, passive smoking, insecticides). The complex pathogenesis of cancer was dissected in an epidemiologic-experimental study in cows, which had intestinal papillomas and carcinomas. Endogenous genetic factors may also play a role in pathogenesis, as is evidenced by species, breed (Boxer!), and family related aggregates of tumour diseases. Epidemiology may provide a means to prevent tumour diseases by, for example, withdrawal of hormones (mammary cancer) or isolation of tumour-virus positive animals (malignant lymphoma).

Expression of the gene encoding growth hormone in the human mammary gland.

Progestins cause a syndrome of growth hormone (GH) excess and enhanced mammary tumorigenesis in the dog. This has been regarded as being specific for the dog. Recently we reported that progestin-induced GH excess originates from foci of hyperplastic ductular epithelium of the mammary gland in the dog. In the present report we demonstrate by reverse-transcriptase PCR and immunohistochemistry that a main factor involved in tissue growth, i.e. GH, is also expressed in normal and neoplastic human mammary glands. The gene expressed in the human mammary gland proved to be identical to the gene encoding GH in the pituitary gland. The role of progesterone in the GH expression of the human mammary gland needs, however, to be proven. It is hypothesized that this locally produced hGH may play a pathogenetic role in breast cancer.

Uterine carcinomas in mother cats after intrafetal inoculation of allogeneic tumor cells (K248 C and P).

Three out of 13 queens that had undergone injection of tumor cells from an allogeneic feline mammary carcinoma cell line through the wall of the pregnant uterus developed a carcinoma of the uterus. The possible role of immune tolerance associated with pregnancy and/or major histocompatibility complex (MHC) compatibility is discussed.

DNA flow cytometry of canine mammary tumours: the relationship of DNA ploidy and S-phase fraction to clinical and histological features.

The DNA ploidy status and S-phase fraction (SPF) of benign proliferative lesions (BPL) and malignant tumours (MT) in the mammary glands of dogs were determined by flow cytometric analysis and the results were related to their clinical and histological features. Seven (14.3 per cent) of 49 BPL and 16 (48.5 per cent) of 33 primary MT had aneuploid G0,1 peaks (P < 0.001). Hypodiploid G0,1 peaks were found in one BPL and in five primary MT. The DNA ploidy status of primary MT was not found to be associated with their size, nodal status, grade of histological malignancy or nuclear grade. In several cases there was intra-tumour heterogeneity in ploidy status independent of histological heterogeneity. The SPF was significantly higher in 27 primary MT than in 45 BPL when diploid and aneploid cases were combined for comparison (P < 0.05), but not when only diploid cases were compared. Among the primary MT the SPF was higher in aneuploid than in diploid tumours (P < 0.05) and it was higher in five MT from five dogs with regional disease than in 22 MT from 19 dogs with local disease (P < 0.05). The SPF was positively correlated with the grade of histological malignancy (P < 0.05) but not with nuclear grade.