Concurrent benign and malignant multiple meningiomas in a cat: clinical, MRI and pathological findings

Abstract

nodes. Only a few individuals (7 per cent) had visceral tuberculous lesions affecting the lungs, mandibular salivary gland, liver, spleen, visceral and parietal pleura and peritoneum. Two individuals (3-8 per cent) had lesions in the foreleg and hindleg joints. The lesions appeared most frequently as caseocalcareous tubercules of up to 5 cm in diameter or as 1 mm miliary foci. Caseation was predominant, being present in 83 per cent of the head lymph node lesions, 65 per cent of the thoracic lymph node lesions and 50 per cent of the abdominal lymph node lesions, while calcification was less abundant, being found in 17 to 27 per cent of the lymph node lesions. The smallest foci (1 mm) were found most frequently in the abdominal lymph nodes (40 per cent). The most chronic and largest tuberculous lesions were typically observed in the lymph nodes of the head and consisted of well-organised granulomas with abundant central necrosis and calcification, encased in a thick fibrotic capsule. A cellular layer composed of macrophages, lymphocytes, epithelioid cells and scarce giant cells was present subjacent to the capsule and surrounding the necrotic centres. The giant cells, when present, were irregular in shape and size, but classical Langhans' giant cells were rarely observed. Lesions representing earlier stages of development were most often present in the lungs, liver and spleen, and consisted of small granulomas with central infiltration of neutrophils and single-cell necroses. Tuberculous lesions in the organs were seen to have grown expansively, compressing the surrounding parenchyma. There were very few acid-fast organisms in the lesions in the Ziehl-Neelsen-stained sections. The larger size and chronicity of the lesions in the head, such as those in the mandibular lymph nodes, suggested that these sites were involved at an early stage of infection, while the smaller granulomas in various organs had the appearance of secondary haematogenous dissemination. A combination of lesions at different stages of development within the same sections suggested repeated re-seeding ofM bovis. Shedding of mycobacteria is likely to occur in the saliva, as gross lesions were observed in the mandibular salivary gland, and were histologically shown to be growing and breaking into the lumen of excretory ducts (Fig 2). The identification of the mandibular lymph nodes as an important target for M bovis in free-living wild boar is consistent with previous reports (Bollo and others 2000) and is relevant for the veterinary inspection of game meat. More studies are required to elucidate the role of the European wild boar in the epidemiology of bovine TB. ACKNOWLEDGEMENTS