A case of multicentric lymphoma with a mixed cell population of large to small round cells with the same nuclear features in a pig was studied immunohistochemically. Neoplastic tissues were composed of 20-50% B-cell lymphoma cells with lambda-type light chain restriction, and 50-80% cluster of differentiation (CD)3+ T-cells. These findings were similar to those of human T-cell-rich B-cell lymphoma (TCRBCL). In addition, both immunoglobulin IgM and IgG were detected in the cytoplasm of the identical lymphoma cell. This pattern of heavy chain expression appeared to be due to maturational arrest in cellular development at the point of heavy chain class switching, as occurs in biclonal gammopathy in human lymphoid malignancy. This case as TCRBCL containing two types of heavy chains with light chain restriction (IgM-lambda and IgG-lambda) appears to be the first of its kind reported in the English literature for either pigs or domestic animals.
To determine whether cardiac rhabdomyoma (CR) is a hamartoma of fetal cardiac myocyte, we investigated five cases of CRs that spontaneously developed in five 6-month-old hybrid swine with histological, immunohistochemical, and ultrastructural techniques. The cases were four multiple and one solitary neoplasms, which appeared as intraventricular nodules of various sizes without any congenital malformations. Histologically, the large ovoid CR cells with an occasional spiderweb appearance showed a transition from normal-looking cardiac myocytes or rarely from Purkinje cells, but no mitotic figures. Besides large amounts of glycogen, the CR cells contained many PAS-negative, large cytoplasmic vacuoles filled with eosinophilic or fibrillar substance. Immunohistochemically, the CR cells showed intense positivity for desmin and variable positivities for vimentin, alpha-atrial naturiuretic peptide, and proliferating cell nuclear antigen. These positivities were not seen in adjacent cardiac myocytes. Cytokeratin was negative in the CR cells but was positive in fetal cardiac myocytes of early gestation. Rod-like or granular positivity for alpha-actinin in the CR cells was similar to that in nemaline myopathy. Ultrastructurally, the CR cells contained myofibrils that frequently showed myofibrillar degeneration and produced large intracytoplasmic vacuoles. These myofibrils often mingled with nemaline bodies and leptofibrils that continued to the Z bands. T-systems, sarcoplasmic reticulum, and intercalated discs, which are specific features of postnatal cardiac myocytes, were sometimes observed in the CR cells. Increase of glycogen and mitochondria and appearance of atrial-specific granules associated with the Golgi apparatus were other features noted. The present findings have not been reported, even in human CR. From these new observations with the recent report on the occurrence of CR in neonatal piglets, swine CR does not belong to the entity of hamartoma but may be a congenital dysplasia of the perinatal cardiac tissues with myofibrillar degeneration, affecting mainly cardiac myocytes and rarely Purkinje cells. The various immunophenotypic changes including proliferating cell nuclear antigen and the increase and appearance of cytoplasmic elements compared with mature cardiac myocytes can be interpreted as reactive or regenerative changes due to myofibrillar degeneration.
Abstract. Eleven cases of alimentary lymphoma affecting the ileum were observed among 26 cases of swine lymphoma detected by meat inspection in Kochi, Japan. The ileal lymphomas were located in the Peyer's patches, along with early involvement of regional lymph nodes, and showed a characteristic pattern of follicular invasion leading to diffuse growth. Following the National Cancer Institute Working Formulation, 10 neoplasms were classified as diffuse, large, noncleaved cell lymphomas and one neoplasm was a diffuse, mixed, small to large cell lymphoma. Both types of lymphoma featured numerous intermingled "starry sky" histiocytes. The lymphoma cells tended to infiltrate into the muscular layer of the ileum in an "Indian file" pattern. Two cases also showed transserosal metastasis into the abdomen and leukemic change. The lymphoma cells showed membrane positivity for alkaline phosphatase and diffuse cytoplasmic staining for acid phosphatase and nonspecific esterase. Monoclonal intracytoplasmic immunoglobulins were demonstrated in nine neoplasms (IgM-X in seven, IgG-X in one, and IgG-K in one). In the areas of follicular invasion, an attenuated network of follicular dendritic cells was visualized via an antiserum against the p subunit of S-100 protein. Ultrastructurally, strands of dilatated rough endoplasmic reticulum and scattered or clustered dense bodies were noted. When compared with feline and human alimentary lymphoma, including Burkitt's lymphoma, the present neoplasms possessed distinctive features, such as originating in Peyer's patches, transserosal metastasis, and predominantly large B cell type with IgM-X type immunoglobulin expression, although some features were similar.
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