Bronchiolar-alveolar adenoma in a rhesus monkey (Macaca mulatta).

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Nonhuman primates have a low incidence of spontaneous neoplasia, with only a few published reports of pulmonary neoplasms in Old World monkeys. A review of the literature identified only three reports of spontaneous primary pulmonary neoplasms in macaques: l) a bronchioloalveolar carcinoma with metastases to bronchial lymph node, spleen, liver, kidney, and brain in an adult female bonnet macaque, Macaca uadiata, 2) a clear cell carcinoma in a female pigtailed macaque, Macaca nemestrina, and 3) a carcinoid in an adult female rhesus monkey, Macaca mulatta.4~x~') Other reported primary pulmonary neoplasms in macaques include carcinomas induced in rhesus monkeys by exposure to beryllium and multiple bronchial adenomas in a rhesus monkey exposed to 1,100 roentgens of x-radiation.I.l0 An adult male rhesus monkey (an old retired breeder) was used in an acute terminal surgical neuroanatomy study. Prior to 1982, the monkey had received several doses of cocaine; since 1982, he had been on no experimental protocols until his use as a control animal in the neuroanatomy study in October 1992. Following euthanasia by pentobarbital overdose, the body was perfused with a formalin/glycerol mixture via the left ventricle, the brain was removed by the investigator, and the animal was submitted to the pathology unit for routine necropsy. At necropsy, changes typical of lung mite (Pneurnonyssus simicola) infestation were found, including fibrous pleural adhesions, pleural scars, dilated bronchioles, and a fine black granular pigment disseminated throughout the lung and in the tracheobronchial lymph nodes. Additionally, there were multiple firm, solid, pale-tan nodules, ranging from barely perceptible up to 4 mm diameter, scattered through all lung lobes. With the exception of colonic diverticulosis, other organ systems were grossly unremarkable. Sections of lung, liver, spleen, and heart were immersed in 10% neutral buffered formalin, trimmed, and embedded in paraffin blocks. Six-micrometer-thick sections were cut on a microtome and stained with hematoxylin and eosin (HE). Sections of lung were additionally stained with alcian blue and by the periodic acid-Schiff reaction. Histologically, lungs contained multiple cellular nodules of two types. The majority of nodules were 3-4 mm in diameter and oriented around ectatic bronchioles. Affected bronchiole walls were thickened by an inflammatory infiltrate of eosinophils, lymphocytes, plasma cells, macrophages, and multinucleated giant cells, with fibrosis, lymphoid nodules, hypertrophy and hyperplasia of the smooth muscle, and phagocytized light tan to black granular anisotropic pigment. Multiple cross sections of metazoan parasites, consistent with lung mites, were present in many affected bronchioles. The second nodular type was scattered randomly throughout the lungs. These nodules, 1-2 mm in diameter, were slightly expansile, infiltrative, unencapsulated cellular masses composed of short papillae that projected into and sometimes filled air spaces and effaced normal pulmonary architecture (Fig. 1). The papillae were formed by a single layer of columnar epithelial cells covering fibrovascular stromal cores, which sometimes contained small bundles of smooth muscle. The epithelial cells had distinct cell borders and single uniform ovoid nuclei oriented along the basal laminae (Fig. 2). Nuclei had evenly dispersed finely stippled chromatin and single small, indistinct nucleoli. Mitotic figures were rarely found. Along the margins of the nodules, the columnar cells blended smoothly with the preexisting bronchioles and alveoli, with no capsule and only slight compression ofadjacent air spaces (Fig. 3). Sections stained with alcian blue and the periodic acid-Schiff reaction demonstrated no mucus production by the epithelial cells.