Canine smooth muscle tumors: A clinicopathological study.

Canine smooth muscle tumors (SMTs) commonly develop in the alimentary and female genital tracts and less frequently in soft tissue. The definition of histological criteria of malignancy is less detailed for SMTs in dogs than in humans. This study evaluated the clinicopathologic features of canine SMTs and compared the veterinary and human medical criteria of malignancy. A total of 105 canine SMTs were evaluated histologically and classified according to both veterinary and human criteria. The Ki67 labeling index was assessed in all SMTs. Estrogen receptor (ER) and progesterone receptor (PR) expression was evaluated for soft tissue SMTs. Follow-up data were available in 25 cases. SMTs were diagnosed in the female genital tract (42%), alimentary tract (22%), and soft tissue (20%). Soft tissue SMTs frequently arose in the perigenital area, pelvic cavity, and retroperitoneum. A subset of soft tissue SMTs expressed ER and/or PR, resembling the gynecologic type of soft tissue SMT in humans. SMTs were less frequently malignant when assessed with human criteria than with veterinary criteria, better reflecting their benign behavior, especially in the genital tract where human criteria tolerate a higher mitotic count for leiomyoma. Decreased differentiation was correlated with increased proliferation, necrosis, and reduced desmin expression. Mitotic count, Ki67 labeling index, and necrosis were correlated with metastases and tumor-related death. Further prognostic studies are warranted to confirm the better performance of the human criteria when assessing SMT malignancy, especially genital cases, to confirm their usefulness in ER/PR-expressing soft tissue SMTs, and to better define the most useful prognostic parameters for canine SMTs.

Canine Gastrointestinal Spindle Cell Tumors Efficiently Diagnosed by Tissue Microarray-Based Immunohistochemistry.

Tissue microarray (TMA) is a time- and cost-saving technique allowing the simultaneous immunohistochemical evaluation of multiple tissue samples. The aim of this study was to assess the efficacy of TMA at classifying canine gastrointestinal spindle cell tumors as gastrointestinal stromal tumor (GIST), smooth muscle tumor (SMT), and non-GIST/non-SMT based on the expression of α-smooth muscle actin (α-SMA), desmin, and CD117. Thirty-four cases were investigated on TMAs, sampling 2 cores each. Immunohistochemistry was performed on TMAs and full sections, and the results were compared. Comparing full sections, TMA specificity and sensitivity were 100% and 93.8%, respectively, for α-SMA; 100% and 80.8% for desmin; and 100% and 100% for CD117. TMA allowed the identification of 6 of 6 GISTs, 25 of 26 SMTs, and 2 of 2 non-GIST/non-SMTs. One SMT was misdiagnosed as non-GIST/non-SMT. Based on these results, TMA-based immunohistochemistry is efficient at diagnosing canine gastrointestinal spindle cell tumors and might be applied on large caseloads in a research setting.

Uterine smooth muscle tumors in potbellied pigs (Sus scrofa) resemble human fibroids: a potential animal model.

Uterine leiomyomas, commonly termed fibroids. clinically affect approximately 25% of women of reproductive age in the United States, with a subclinical incidence as high as 77%. The pathogenesis of fibroid formation remains poorly understood, due in large part to the lack of a suitable animal model. This retrospective study characterizes the clinical, gross, and histopathologic features of similar, spontaneously occurring uterine tumors in potbellied pigs. Medical records available through a local Potbellied Pig Spay/Neuter Program, pig sanctuaries, and the Duchess Fund database were reviewed for evidence of reproductive disease or surgery. One-hundred and six female potbellied pigs were evaluated and uterine neoplasia was identified in 17 animals: tissues were available for 13 of these. Uterine leiomyoma was diagnosed in 11 of 13 cases, leiomyosarcoma in 1 of 13 cases, and undifferentiated sarcoma in 1 case. Pigs presented with clinical signs including abdominal distension or vaginal bleeding or were subclinical and identified during ovariohysterectomy. Tumors ranged from microscopic to 45 kg, were often multiple, and primarily involved the uterine horns. Hematoxylin and eosin and trichrome-stained sections were evaluated for morphological features of human and animal leiomyomas: immunohistochemistry to detect smooth muscle actin was also performed. The cellular pattern/morphology and variable degree of fibroplasia of the leiomyomas were similar to that reported for human fibroids. These results support further investigation of uterine leiomyomas in potbellied pigs as a potentially valuable animal model for studying human fibroids.

Genetic relationship among lines and smooth muscle and ovarian follicular development within lines of Japanese quail in two long-term selection studies.

Smooth muscle tumor and ovarian follicular development were studied in lines of Japanese quail selected for increased 4-wk BW (HW, P, and T) and their randombred controls (C and R1). The lines studied were from long-term selection studies at The Ohio State University (HW and R1) and The University of Georgia (P, T, and C). To study the genetic relationship among the lines in the two selection studies, the C, P, HW, and R1 lines were DNA-fingerprinted by digestion of the DNA with the HaeIII restriction enzyme and using Jeffreys' 33.6 probe. The BW of females at 4 wk of age and at the end of a 240-d egg production period were similar for the C and R1 lines. The BW of the selected lines was ranked P > T > HW for both measurements. Smooth muscle tumors were found in the oviducal ligaments adjacent to the magnum. A greater percentage of hens from the BW-selected lines had smooth muscle tumors of greater weight than the randombred control lines, which did not differ in tumor incidence or weight. The P and T lines had a greater incidence of multiple-lobed tumors than the HW line. Based on bandsharing (BS) of DNA fingerprints, the Georgia and Ohio lines did not appear to be closely related, suggesting that, perhaps, the smooth muscle tumors in the BW-selected lines in the two studies might have resulted from pleiotrophic effects of genes affecting growth or to genes closely linked to the growth genes. The BW-selected lines in both selection studies had more ovarian follicles in rapid development, which were of greater weight, than the randombred control lines. The HW line had a larger number of ovarian follicles in rapid development than the P and T lines. The percentage of hens with atretic follicles was greater in the BW-selected lines. The results of the present study suggest that the effect of BW selection on ovarian follicular development may occur early in selection (within the first 30 generations) and is not influenced by additional genetic changes in BW.

Hypoglycemia in four dogs with smooth muscle tumors.

Tumor-associated hypoglycemia has been reported in dogs with pancreatic beta-cell tumors, hepatic tumors, and, rarely, with other neoplasms. This article describes 4 dogs with marked hypoglycemia associated with smooth muscle tumors (jejunal leiomyoma, gastric leiomyoma and leiomyosarcoma, and splenic leiomyosarcoma). Presenting clinical signs included grand mal seizures, lethargy, weakness, ataxia, and, in 1 dog, polyuria/polydipsia. The serum insulin concentration was low in 1 dog and normal in the other dog evaluated. Immunohistochemical staining for insulin was negative in the 4 tumors; the 3 tumors arising from the stomach and jejunum stained diffusely positive for glucagon. Blood glucose concentrations rapidly returned to normal after complete surgical resection of the tumors, and clinical signs associated with hypoglycemia resolved. Long-term follow-up available in 3 of the 4 dogs found no recurrence of clinical signs related to hypoglycemia at 15, 31, and 38 months after surgery, respectively.

Biological behaviour and morphological characteristics of a transplantable tumour derived from a uterine smooth muscle tumour in the F344 rat.

A subcutaneously transplantable tumour (SMT-Y) was established from a smooth muscle tumour arising from the uterus of a female F344 rat. SMT-Y was serially passaged by subcutaneous implantation into syngeneic female rats up to the 15th generation, but transplantation failed in males. The rat with the primary uterine tumour also had mononuclear cell leukaemia (MCL), and MCL cells grew concurrently in implanted rats. At passage five, MCL cells were eliminated from transplants by implanting the central part of an SMT-Y nodule, consisting only of neoplastic smooth muscle cells. SMT-Y at passages six to 15 was examined biologically and morphologically. The primary tumour and SMT-Y tumours consisted mainly of interlacing fascicles of elongated and fusiform neoplastic smooth muscle cells with abundant cytoplasm. Occasional cells showed nuclear atypia. Mitosis counts per 10 high-power microscopic fields in the primary tumour and SMT-Y ranged from 11 to 36. Neoplastic cells reacted positively for desmin, muscle actin and myosin, but not for myoglobin. Electron microscopy revealed cytoplasmic myofilaments with oval dense bodies. These findings suggested a smooth muscle origin of SMT-Y and it was regarded as a leiomyosarcoma by the criteria for human uterine smooth muscle tumours. Despite the malignant histological features, SMT-Y grew slowly into a large nodule, with an average diameter of 5 cm and average weight of 81 g, 24 weeks after transplantation. Neither invasive tumour growth nor metastases were observed in SMT-Y-bearing rats.