THYMOMA IN A CHICKEN (GALLUS DOMESTICUS)

Transcription

1 THYMOMA IN A CHICKEN (GALLUS DOMESTICUS) WILLlAM H. FELDMAN, D V.M, M.S. (From the DiviJion of Bxperiinentnl Medicine, Tlar Muyo Foundation, Rochester, Minnesota) The rarity of neoplasms of the thymus gland in man and in the lower animals would seem to justify the description of such a tumor which was recently observed in a chicken (Gallus domesticus). REPORT OF A CASE A rooster of the Barred Rock breed, aged two to three years and in good flesh, was selected with others for killing and subsequent use for food. The neck was cut across rather close to the thorax, and the cutting instrument severed also the posterior portion of a large tumorous mass which occupied the ventral aspect of the cervical region extending from the thoracic aperture forward for a distance of 10 cm. (Fig. 1). The abundant plumage had prevented this large tumor from being seen until the neck had been severed from the body in the slaughtering process. The mass, which weighed approximately 250 gm., had encroached on the wall of the crop and pushed this organ to one side. The dimensions ol the tumor were 10 by 5 by 4 cm. It was firm, homogeneous and of a dirty flesh color, with occasional irregular foci of necrosis. The mass was situated suhcutaneously and was freely movable in the connective tissue elements ventral to the trachea and the cervical vertebrae. Careful macroscopic examination failed to reveal metastatic tumors in any of the organs or tissues. Histopntlzology. Sections prepared from various portions of the tumor, for microscopic cxnmination, disclosed ;i richly cellular structure composed largely of intertwining sheets or bundles of polymorphic cells (Fig. 2). These elements had slightly acidophilic cytoplasm and relatively large nuclei which stained poorly with the basic dye and in which was rather evenly distributed a small amount of finely granular chromatin material. Nucleoli, although demonstrable, were not prominent. An occasional small lymphocyte was seen. The polymorphic character of the cells was well shown in certain fields where large numbers of the cells, arranged parallel with one another, had a compressed, spindle-like shape, while near by cells, arranged in less orderly fashion, revealed wide variation in contour and size. A moderate number of cells were undergoing mitotic division and in sections from onr of the areas studied, concentric whorls of closely packed cells morphologically resembling I~assall s corpuscles were seen (Fig 3). These structures were noi numerous and occurred in SO far as could be determined in sections from only one portion of the tumor. Lymphoid tissue such as characterizes the normal thymus gland of the chicken was present in minimal amounts and usually as small, isolated foci. The structure was well supplied with blood vascular channels which seemed to reveal a predilection for the regions containing the lymphoid tissue. In some portions of the tumor fibrosis was much in evidence and the presence of abundant reticular stromii was strikingly revealed in sections that were appropriately stained (Fig. 4). With the exception of the lung, a11 tissues examined were without morphologic evidence of disease. The lung contained some features that were difficult to interpret, since there were changes suggestive of metastasis but lacking leatures necessary to determine this dehnitely. Accumulations of cells similar to those making up the bulk of the large tumor in the neck weresfound in the peribronchial tissues in one of the sections, and in another part of the same lung were a considerable number of alveolar-like collections of slightly acidophilic polymorphic cells which bore marked resernhlance to those of the major tumor. The picture was confused by the presence of an enormous number of acidophilic granulocytes, inononuclear cells, mucus, fibrin, and other features suggestive of an inflammatory reaction. I Submitted for publication Nov 22,

2 FIG. 1. TIIYMOMA IS A CIIICKEN: LARGE TUMOR IN POSTERIOR HALF OF CERVICAL REGION FIG. 2. PHOTOMICROGRAPH SIlOWING RICHLY CELLULAR STRUCTURE COXSISTING LARGELY OF POLYMORPHIC CELLS ( X 660) 577

3 578 WILLIAM 1%. FELDMAN COMMENT The large tumor of the inferior cervical region was considered to be a thymoma probably derived from elements of the reticulum of the thymus gland. In the adult chicken the thymus usually consists of three pairs of glands. The glands are of a slightly yellow color, 0.3 cm. to 0.4 cm. in length, and occur on both sides of the trachea following the course of the jugular veins. The posterior pair of glands occurs near the thoracic aperture; the anterior pair is near the larynx or slightly posterior to that organ, and the middle pair occupies an intermediate position. The size of the glands is such that in normal adult birds they are seldom observed. According to Reinhardt they may become hyperplastic in leukosis and it is not uncommon to see them extensively involved in cases of chronic generalized tuberculosis of chickens. Primary tumors of the thymus are rare not only in chickens but in the domesticated species of mammals as well. Among 332 primary epithelial malignancies of horses reported by Sticker there was only one that coulg be considered as possibly thymic in origin. Trautmann reviewed the literature pertaining to thymic tumors in animals prior to 1924 and stated that the cow is most frequently affected and that most of the thymic tumors are malignant, although they usually grow slowly. Trautmann questioned the correctness of the diagnosis of several cases of so-called thymic tumor of the lower animals. Among approximately 1000 neoplasms of domesticated mammals in my collection there are only two that originated from the thymus gland. One occurred in an old female sheep and the other in a ten-year-old cow of the Jersey breed. The only reference in the literature to a primary tumor of the thymus of a chicken is that by Saupe. Since the report as originally published was not available, information concerning the details of this case cannot be included in this communication. The tumor which is the subject of this report was considered of thymic origin for the following reasons: (1) anatomically it arose in a region where thyinus tissue occurs; (2) the neoplasm is definitely dissimilar to an epithelioma such as might arise from the skin and likewise differs in appearance from the rather common lymphoblastic tumor of chickens known as lymphocytoma (Feldnian) ; (3) the predominance of peculiar polymorphic cells, many of which were undergoing mitosis, suggests a genetic relationship of these cells to the reticular elements of the thymus gland; (4) structures occur in the tumor resembling or simulating Hassall s corpuscles. SUMMARY A large tumor composed of elements thought to be derived from the reticulum cells of the thymus gland of an adult male chicken is described. The growth, which weighed approximately 250 gm., occurred in the ventral cervical region, extending from the thoracic aperture anteriorly for a distance of 10 cni. Definite metastasis was not observed, although a few cellular accumulations suggestive of metastasis were present in one lung.

4 FIG. 3. PHOTOMICROGRAPH SIIOWING CONCENTRIC ACCUMULATION or CELL SIMULATING A HASSALL S CORPUSCLE (x 660) FIG. 4. PHOTOMICROGRAPH SHOWIKG FIBRILLARETICULUM (X 380) 579

5 5 80 WILLIAM H. PELDMAN BIBLIOCRAPIIY 1. FELDMAN, W. H.: Neoplasms of Domesticated Animals, I hiladelphia, W. B. Saunders Co, 1032, p REINHAKDT, R. : Die pathologisch-anatomischen Veranderungen bei den spontanen Krankheiten der Hausvogel, Ergebn. d. allg. Path. u. path. Anat. 23: , SAUPE: Diss., Munchen, 1923, quoted by Reinhardt 4. STICKER, ANTON: Ueber den Krebs der Thiere, Arch. f. klin. Chir. 65: ; , TRAUTMANN, ALFRED: Drusen rnit innerer Sekretion (Inkretion) endokrine Drusen Blutdrusen, in Joest, Ernst : I-Iandbuch der speziellen pathologischen Anatomie der Haustiere. Berlin, R. Schoetz, Vol. 3, pp , 1923.