Thymic Carcinoma with Neuroendocrine Differentiation in a Calf.

Abstract

ABSTRACT. A neuroendocrine carcinoma originating in the thymus was found in a 7-month-old, castrated male, Japanese Black calf. The neoplasm consisted largely of very primitive cells, characterized by the paucity of cytoplasmic organelles, but a few cells were immunoreactive for somatostatin or neurofilaments. The expression of both cytokeratin and neurofilament protein was a feature of neuroendocrine differentiation. This neoplasm considered to be a tumor of a thymic stem cell, with little but indubitable evidence of differentiation into somatostatin-producing cells.-KEY WORDS: bovine, somatostatin, thymic carcinoma.J. Vet. Med. Sci. 61 (7): [853][854][855] 1999 electron microscopical examination, small blocks taken from formalin-fixed tissues were post-fixed in 1% osmium tetroxide, embedded in epoxy resin, stained with uranyl acetate and lead citrate, and examined by electron microscopy. Histologically, the neoplastic tissue in the mediastinum consisted of clusters or sheets of closely packed neoplastic cells, enclosed by variously developed collagenous fibrous tissue (Fig. 1), and was accompanied with necrotic or hemorrhagic areas. Neoplastic cells invaded the pleura and were present mainly within lymphatics, but only few neoplastic cells were detected within pulmonary alveoli. The neoplastic cells were large and polyhedral, and on occasion very large cells were detected. The nuclei were large and oval, with prominent or moderately prominent nucleoli and finely clumped chromatin. The cytoplasm was eosinophilic and relatively narrow. Mitotic figures were occasionally seen. Similar morphological features were observed in the other invasive or metastatic lesions.Immunohistochemically, somatostatin-, chromogranin-, or NF-positive cells were found in the neoplastic tissue albeit extremely rare (Fig. 2). Many neoplastic cells were positive for cytokeratin (Fig. 3) or NSE.Ultrastructurally, the neoplastic cells had ovoid nuclei containing plentiful euchromatin, but at times showed indented nuclear contours. There were poorly developed organelles in the cytoplasm. It was rare to find cells containing small numbers of dense-core secretory granules (Fig. 4), sparsely distributed glycogen granules, one or more low density lipid droplets, or globular bodies composed of intermediate filaments. Tight junctions and immature desmosomes were detected between adjoining cells. Cell borders were smooth, but on rare occasions intercellular lumina bearing microvilli were formed (Fig. 5).

Ectopic cervical thymic carcinoma in a dog

“…In veterinary medicine, malignant thymoma and thymic carcinoma are used interchangeably, the latter being specifically defined as thymic epithelial neoplasia (Jacobs and others 2002). To the author’ knowledge, there are only single case reports of a dog with a thymic adenocarcinoma (Abdi and Elliott 1994) and a calf with thymic carcinoma showing neuroendocrine differentiation (Anjiki and Kadota 1999). Here, the presence of neoplastic emboli in the thyroid vessels confirms metastatic capability and malignant behaviour.…”

Peritoneal and scrotal carcinomas of unknown origin in two bovine calves

“…Carcinomas are rarely reported in calves. 11 A thymic carcinoma has been reported in a calf, 1 as well as ethmoid carcinoma, 12 bronchoalveolar carcinoma, 20 and anaplastic small cell carcinoma of the lung. 15 Two undifferentiated carcinomas in adult cows were examined ultrastructurally in one report, and were found to be squamous cell carcinoma and adenocarcinoma of the lung.…”