Lymphomatoid granulomatosis is a rare human disease that has been recently reported in young dog^.',^.^.^ Lymphomatoid granulomatosis, as originally described in human beings by Liebow et al.,5 is an angiocentric and angiodestructive lymphoreticular proliferative and granulomatous disease that predominantly involves the lungs. Pathologically, it is a peculiar angiocentric lymphoid lesion with a lymphomalike appearance (lymphomatoid) in some areas and necrosis (granulomatosis) in others. The proliferative infiltrate is composed of atypical lymphoreticular cells admixed with variable proportions of lymphocytes, plasma cells, and histiocytes. A clinically normal, 8-month-old, male Beagle was not included in drug safety studies owing to a persistent eosinophilia (3.2-4.2 103/mm3). The dog was euthanatized at 15 months of age as a result of a sudden deterioration of its condition: a marked abdominal enlargement, a 3.7 kg increase in body weight during the last 2 weeks, and severe respiratory problems, including coughing. At necropsy, the abdomen contained about 2.5 liters of a clear fluid; the liver was congested. The accessory lobe of the right lung was enlarged (1 2 x 13 cm), firm, and pale yellow. The overlying pleura was smooth and dull. Cut sections revealed coalescing multinodular pale tissue centered around bronchi that compressed the remaining lung peripherally. Grey or dark-red patches were scattered throughout all lobes. A white, firm tissue replaced the markedly enlarged tracheobronchial lymph nodes (5 x 3 cm) and was found focally in the sternal lymph node. Other organs were unremarkable. Tissues were fixed in 10% neutral buffered formalin, routinely processed to paraffin sections, and stained with hematoxylin and eosin, and Gomori's trichrome stain with Weigert's stain for elastin fibers. Sections were stained immunocytochemically by the peroxidase anti-peroxidase technique using rabbit anti-bovine S100 protein (Dakopatts, Issy-les-Moulineaux, France) with a silver amplification (Amersham, Les Ulis, France), and by peroxidase-labeled protein A (New England Nuclear, Paris, France) with trypsinization, using goat anti-human a1 -anti-trypsin, goat antihuman lysosyme followed by a rabbit anti-goat immunoglobulin G (Nordic, Le Perray en Yvelines, France). For negative controls, duplicate sections were incubated with normal, nonimmune rabbit or goat serum instead of the primary antibody. Lymph node and brain were used as positive controls. Formalin-fixed portions of the accessory lobe of the right lung were divided into 1 mm3, immersed in 2.5% glutaraldehyde in 0.1 M phosphate buffer (pH 7.37), post-fixed in 2% osmium tetroxide, and embedded in epoxy resin. U1trathin sections were stained with uranyl acetate and lead citrate and examined with a Zeiss EM109 electron microscope. Microscopically, the tumor was composed of sheets of dense infiltrates of atypical pleomorphic lymphoid cells that obliterated normal structures (Fig. 1). Most cells were polygonal to oval and had a faintly basophilic, moderately abundant cytoplasm. Nuclei varied from rounded to slightly elongated. Chromatin was predominantly stippled and occasionally coarse. Many cells had up to four round amphophilic nucleoli. There were atypical vesicular or cleft nuclei. Scattered binucleated cells were present. The fine fibrovascular stroma was predominantly infiltrated by eosinophils, fewer plasmocytes, and occasional Mott cells. Individual cell necrosis was observed throughout the tissue. No immunoreactivity for lysozyme, a-I-antitrypsin or S-100 protein was seen in tumor cells. Many large blood vessels were infiltrated by pleomorphic lymphoid cells and eosinophils. Their centers were occupied by a variously-shaped fibrous tissue that delineated vascular channels and was connected to the fibrous wall that merged with the surrounding stroma (Fig. 2). They had no elastic lamina. There were occasional epithelial remnants of airways and necrotic foci up to 3 mm in diameter. The overlying pleura was thickened and fibrotic. Sections at the margins of the tumor revealed that the process originated from pulmonary arteries and compressed adjacent airways (Fig. 3). The intimae of some affected pulmonary arteries were thickened by edema, fibrosis, eosinophils, and atypical lymphoid cells. Histologic lesions of allergic bronchitis3 with a few, small, foreign-body granulomas corresponded to the patches seen at necropsy in the other lobes. Blood vessels in these areas were spared. The sternal lymph node was multifocally invaded by tumor cells. Histologic liver changes were consistent with acute passive congestion. Heart, kidney, spleen, thyroid, and muscle were unremarkable. Ultrastructurally, tumor cells lacked intercellular junctional complexes and pericellular basement membrane material (Fig. 4). A limited amount of cellular interdigitations was observed. Nuclei were ovoid or variably folded and had large, often multiple, nucleoli. The cytoplasm contained moderately abundant profiles of granular endoplasmic retic-
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Dec 1, 2005
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