Abstract. The immunohistochemically determined estrogen receptor (ER) ␣ (ER␣) and progesterone receptor (PR) status, as well as recognized, well-accepted prognostic indicators and host factors were prospectively analyzed in 84 cases of primary canine mammary carcinoma for their effect on disease-free period (recurrence free, metastasis free, or combined) (DFP) after an observation period of 18 months. The presence of one or both receptors, as well as tumor size, lymph node status, histologic grading, intravascular growth, and necrosis, were of prognostic value for DFP. In multivariate analysis, only tumor size and histologic grading proved to be independent prognosticators. None of the host factors analyzed were of prognostic value for DFP. ER␣, PR, or both were detected in 173 out of 228 tumors: 70 ER␣ and PR; 5 ER␣ only; 98 PR only. Statistically significant differences regarding the presence of one or both receptors were observed between benign and malignant tumors and between complex, mixed, and simple histologic subtypes of benign and malignant tumors. In the group of malignant tumors (n ϭ 155), the presence of one or both receptors was more frequent in tumors smaller than 3 cm, without lymph node metastasis, with tubulopapillary rather than solid patterns of growth among simple carcinomas, of histologic grades I and II, without both intravascular growth and necrosis, and with lymphocyte cell infiltrates. The most frequent groups of hormone receptors-positive tumors were the ER␣-positive and PRpositive group among benign and the ER␣-negative and PR-positive group among malignant tumors.

The immunohistochemical expression of muscle actin has been studied in 45 canine hemangiopericytomas (CHP) using a monoclonal antibody (HHF35) and formalin-fixed, paraffin-embedded specimens. The distribution of vimentin, desmin, cytokeratins, lysozyme, factor VIII-related antigen, S-100 protein, and glial fibrillary acidic protein was studied both in CHP and in some canine soft-tissue neoplasms (seven fibrosarcomas, seven benign schwannomas, seven benign fibrous histiocytomas, and six leiomyosarcomas) used as controls for differential diagnosis. All CHP and control tumors expressed vimentin. Twenty-three CHP expressed muscle actin, whereas all control tumors analyzed were muscle actin-negative, with the exception of leiomyosarcomas. Among muscle actin- and vimentin-positive CHP, one case could be reclassified as leiomyosarcoma because it was desmin-positive, two cases expressed lysozyme, and nine cases expressed S-100 protein. Among muscle actin-negative and vimentin-positive CHP, seven expressed S-100 protein. In addition, S-100 protein was detected in five schwannomas. All CHP and control tumors analyzed were negative for cytokeratins, factor VIII-related antigen, and glial fibrillary acidic protein. Our results support the hypothesis of a pericytic origin of CHP, and suggest that muscle actin, desmin, vimentin, and lysozyme could be useful for the differential diagnosis of canine spindle cell tumors, but not all these neoplasms can be identified with these tumor tissue markers.

Estrogen (E) is a key regulator of the synthesis and secretion of pituitary reproductive hormones [luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin (PRL)]. Until recently, it was thought that all biological actions of E at the pituitary were manifested through a single E receptor (R). The pituitary, like many other reproductive tissues, expresses two isoforms of ER, α and β, both activated by E. The relative contribution of α and β forms in E regulatory actions is largely unknown. To this end, 2-week-old ovariectomized (OVX) rats were injected over 3 days with 25 µg estradiol benzoate (EB), 1.5 mg of propylpyrazole triol (PPT), a selective ERα agonist, 1.5 mg of the selective ERβ agonist diarylpropionitrile (DPN) or a combination of PPT and DPN. Controls were injected with 0.2 ml oil. At 10:00 h on the day after treatment, trunk blood was collected to determine serum concentration of LH, FSH and PRL, and pituitaries were processed for RT-PCR analysis of total (A+B) progesterone receptor (PR) mRNA, immunocytochemistry of PR and incubation. Pituitaries from each of the five groups were incubated in DMEM, with or without 20 nM of the antiprogestin at the receptor ZK299, for 3 h with: 10^–8M 17β-estradiol, 10^–6M PPT, 10^–6M DPN, PPT+DPN or medium alone, respectively, to determine LH, FSH and PRL secretion, and, when challenged with two pulses of 15 min 1 h apart of 10^–8M gonadotropin-releasing hormone (GnRH) (GnRH self-priming). EB, PPT and PPT+DPN treatments increased PR mRNA and the number and intensity of nuclei immunoreactive (IR) for PR in gonadotropes, and reduced the number of gonadectomy cells. Like E, PPT alone or in combination with DPN stimulated PRL secretion, increased basal and GnRH-stimulated LH and FSH secretion and induced GnRH self-priming in the absence of ZK299 in the incubation medium. DPN alone had only a significant E-like effect on gonadectomy cells and IR-PR, but not on GnRH self-priming. In addition, while DPN lacked an agonistic action on peripheral tissue and serum pituitary reproductive hormones concentration, EB, PPT and PPT+DPN induced similar uterine ballooning and vaginal cornification, and increased and decreased, respectively, serum concentrations of PRL and gonadotropins. Overall, these results indicate that most of these E actions on the pituitary are exerted through the ERα isoform. The finding that activation of ERβ with its selective DPN agonist had an estrogenic effect on IR-PR nuclei, but not on GnRH self-priming, a characteristic ERα-mediated effect of E, suggests that the biological action of E at the pituitary may involve both isoforms of ER.

We retrospectively evaluated predictive prognostic factors in 73 cats with vaccine-associated sarcoma given postsurgical curative (n=46, most with clean margins) or coarse fractionated radiotherapy (n=27, most with either macroscopic disease or dirty margins). The former animals displayed a median survival of 43 months and a median progression free interval (PFI) of 37 months, the latter reached a median survival of 24 months and a median PFI of 10 months. In cats undergoing coarse fractionated therapy, factors predictive of a better outcome included lack of visible mass (n=10) as opposed to macroscopic disease (n=17, survival: 30 vs. 7 months, P=0.025; PFI: 20 vs. 4 months, P=0.01), adjuvant chemotherapy for gross disease (n=5/17, survival: 29 vs. 5 months, P=0.04) and a smaller number of surgeries preceding radiation therapy (Coeff=0.41, P=0.03). The Ki67-index was not predictive for survival. We concluded that postsurgical curative and coarse fractionated radiotherapy are both effective legitimate options for managing vaccine-associated sarcomas. months and a median PFI of 10 months. In cats undergoing coarse fractionated therapy,

Abstract. The collective immunohistochemical expression of human lysozyme, human alpha-1 -antitrypsin, human CD3 antigen, calf vimentin, human keratins, human lambda light chains, canine immunoglobulins IgG, IgM, and bovine protein S-100 has been analyzed on formalin-fixed, paraffin-embedded tissue sections of 25 spontaneous canine transmissible venereal tumors (CTVT) from both genital and extragenital locations using the avidin-biotin-peroxidase complex technique. Lysozyme immunoreactivity was detected in 10/25 CTVT, alpha-1-antitrypsin in 14/25 CTVT, and vimentin in 25/25 CTVT. All CTVT cells were negative to keratins 5 + 8 of the Moll catalogue (RCK-102), S-100 protein, lambda light-chain immunoglobulins, IgG, IgM, and CD3 antigen. The intratumoral T-and B-lymphocyte infiltrate was differentiated using CD3 antigen, lambda light-chain immunoglobulins, IgG, and IgM, and this technique could be useful to evaluate the regressive or progressive growth stage of venereal tumors. Our findings support the hypothesis of a histiocytic immunophenotype for CTVT, and these staining techniques could be used in the differential diagnosis with lymphomas.Key words: Dogs; immunocytochemistry; round cell tumors; transmissible venereal tumors.Canine transmissible venereal tumor (CTVT) is a round cell neoplasm occurring on external genital mucosae and is transmitted by cell implantation during coitus, licking, or other interaction between an affected dog and a susceptible host in endemic regions.44 Although the tumor primarily spreads locally to the external genitalia21 and metastasis is rare, it has also been reported in the inguinal lymph nodes, skin, lips, and buccal and nasal mucosa1, 3,25,26,35,39 and less frequently in the tonsils, liver, pancreas, spleen, lung, kidney, and mesenteric lymph n~d e~.~x~~.~~,~~,~~,~~ Extragenital occurrence of CTVT without genital lesions has been reported in the nasal cavity,17,20,36,37,46 conjunctiva and eye,'^^,^^ kin,^^,^^ tonsils, buccal muco~a,~O and anal mucosa.6 These atypical locations of CTVT can be due either to a previous regression of the primary genital t~m~r~~,~~ or to implantation of tumor cells on external mucous membranes by licking and ~n i f f i n g .~~.~~ In these atypical cases, it is usually difficult to carry out a differential diagnosis with other canine round cell tumors such as lymphomas, histiocytomas, poorly differentiated mast cell tumors, amelanotic melanomas, and poorly differentiated carcinomas. 15,17,36,46 Although round cell tumors have been immunocharacterized using several tumor markers,2,4J4J9,31,32,43 few immunohistochemical studies on the CTVT have been made so far23,43 and the cell origin and immunophenotype remain Spontaneous regression of CTVT may occur, and recovered dogs can acquire humoral and cellular immunity, which prevents subsequent t~m o r s .~,~~ Some authors have found a significant increase of T lymphocytes infiltrating the tumor masses of spontaneous regressive CTVT. 1,29,45 These lymphocytes were identified using anti-thymocyte sera in fr...