Disseminated Langerhans cell histiocytosis presenting as oesophageal disease in a cat

CASE SUMMARY: An 11-year-old female spayed domestic shorthair cat was referred with a 2-month history of ptyalism, hyporexia and weight loss. Physical examination revealed reduced body condition score (2/9) and decreased skin turgor. Laboratory abnormalities included mild erythrocytosis, elevated creatine kinase, hypercobalaminaemia and hypofolataemia. CT of the head and abdominal ultrasonography were within normal limits. Gastroesophagoscopy revealed mucosal ulceration and possible stenosis of the distal oesophagus. Thoracic radiographs and iodine oesophagram showed a soft tissue opacity in the caudodorsal thorax compatible with a parietal oesophageal mass causing luminal stenosis or an extra-parietal mass causing ventral displacement and compression of the oesophagus. Pulmonary nodules were observed in the cranial lung lobes. CT of the thorax confirmed the oesophageal origin of the mass and the presence of pulmonary nodules scattered throughout the lung parenchyma. The patient was euthanased given the imaging findings and perceived guarded prognosis. Post-mortem examination revealed multifocal nodular lesions affecting the oesophagus, lungs, kidneys and pancreas. Histopathological examination identified atypical round cells characterised by eosinophilic cytoplasm and pale nuclei with prominent nuclear grooves, compatible with neoplastic histiocytic cells. Immunohistochemistry revealed strong expression for CD18, Iba-1 and vimentin. Transmission electron microscopy demonstrated intracytoplasmic organelles consistent with Birkbeck granules of Langerhans cell origin in lesional histiocytes. These findings were compatible with a diagnosis of disseminated Langerhans cell histiocytosis. RELEVANCE AND NOVEL INFORMATION: To our knowledge, this is the first report of disseminated Langerhans cell histiocytosis with oesophageal involvement in a cat.