Extramedullary Plasmacytoma in a Horse with Ptyalism and Dysphagia

Abstract

Abstract. A Clydesdale mare was examined for weight loss, inappetence, ptyalism, and dysphagia. The main abnormality revealed by serum biochemistry was a marked hyperglobulinemia, and protein electrophoresis revealed a monoclonal gammopathy in the gamma region. The urine was positive for Bence Jones proteins. These findings suggested a plasma cell tumor. The neoplasm could not be located with extensive antemortem examination. At postmortem, neoplastic cells morphologically compatible with plasma cells and positive for equine IgG with imunoperoxidase staining infiltrated the pericardium, mediastinal stromal tissues, adrenal glands, meninges, atrioventricular valves, aorta, abdominal and thoracic fat, and nerves, including the trigeminal nerve. The neoplastic cells invading the cranial nerves were responsible for many of the presenting signs.A 10-year-old 604-kg Clydesdale mare was referred to the Veterinary Teaching Hospital at the Atlantic Veterinary College (AVC) for weight loss, inappetence, ptyalism, and apparent dysphagia of several weeks duration. A complete blood count and a serum biochemistry profile evaluated by the referring veterinarian 2 weeks earlier showed no significant abnormalities. The mare had not responded to a short course of intramuscular procaine penicillin.On physical examination at the AVC, the mare had a poor hair coat, normal pulse and rectal temperature, and an increased respiratory rate of 40 breaths/minute. Frequent chewing motions were observed, with saliva dripping from the muzzle. Further examination included a detailed inspection of the oral cavity and endoscopic evaluation of the pharynx, guttural pouches, upper esophagus, and trachea. During endoscopic examination, the only abnormalities were a weak swallow reflex when the endoscope made contact with the laryngeal structures and a large pool of clear tenacious fluid in the distal trachea. The tracheal fluid was aspirated for examination. Cytologic evaluation revealed low numbers of large squamous epithelial cells and numerous bacteria, which was characteristic of saliva. The roots of the teeth were radiographed, but no abnormalities were observed. A clinical diagnosis of dysphagia of unknown neurologic origin was made. No other cranial nerve deficits or gait abnormalities were observed on neurologic examination.Blood was submitted for a complete blood count (CBC) and a serum biochemical profile. The CBC revealed a mild leukocytosis (16.8 ϫ 10 9 /liter; reference range, 5.5-12.5 ϫ 10 9 /liter) characterized by a mild mature neutrophilia (8.568 ϫ 10 9 /liter; reference range, 2.7-6.7 ϫ 10 9 /liter) and a mild lymphocytosis (8.2 ϫ 10 9 /liter; reference range, 1.5-5.5 ϫ 10 9 /liter). The only significant change on the biochemical profile was a marked hyperproteinemia (102 g/liter; reference range, 60-77 g/liter) caused by a hyperglobulinemia (72 g/liter; reference range, Ͻ40 g/liter). Protein electrophoresis showed a narrow spike in the gamma globulin area supportive of a monoclonal gammopathy (Fig. 1) The results were ambiguous w...

Metastatic Tumors to the Adrenal Glands in Domestic Animals

“…19 A plasmacytoma and a hemangiosarcoma with metastases to the adrenals have also been reported in horses. 6,23 Lymphoma and metastatic endometrial carcinoma have been reported to involve the adrenal glands in cats; only 11 cases of metastatic lesions to the adrenal glands of cats were recorded in 24 years in the Veterinary Medical Database. 26,27,29,31,32 A number of secondary tumors to the adrenals have been described in cattle including pulmonary carcinoma, rhabdomyosarcoma, fibrosarcoma, mastocytoma, and lymphoma.…”

“…25,30,36 In domestic animals, metastases to the adrenal glands have only been occasionally described, mostly as single cases. 2,3,[5][6][7][8]10,[19][20][21][22][23][26][27][28][29][31][32][33]35,[37][38][39] To the authors' knowledge, there are no published reports on the rate of adrenal involvement in metastatic disease for specific tumor types in domestic animals. Hypoadrenocorticism due to tumor spread has been reported in two cats but has not been reported in other animals.…”

Hematopoietic Neoplasias in Horses: Myeloproliferative and Lymphoproliferative Disorders

“…The paraprotein may be complete Ig, free light chain, light chain fragments or polymers, or partial Ig missing one or both chains [38]. It is an uncommon neoplasia, and it has been reported in several species, including human beings, cats, dogs, and horses [2, 18, 21, 25, 34, 44, 45, 55]. …”

“…In horses, the main differential diagnosis for monoclonal gammopathies includes multiple myelomas, malignant lymphomas and so-called benign monoclonal gammopathies [18, 33, 69]. In horses and human beings, subclasses of IgG are the predominant paraproteins associated with myeloma, whereas in dogs IgG- and IgA- type multiple myelomas are of equal prevalence [2, 18, 21, 37, 45]. Barton et al .…”

“…Plasmocytosis in the bone marrow is one of the criteria for multiple myeloma in human beings [51] and it has been described also in horses [44, 45]. However, marrow plasmocytosis has been found in diseases other than myeloma [37].…”