Proliferating histiocytic lesion (Histiocytosis-X?).Association of an extensive mediastinal and retroperitoneal sclerosing lesion with Gagel's granuloma of the posterior lobe of the pituitary

A case of an extensive retroperitoneal and mediastinal sclerosing, histiocytic lesion associated with a solitary focus of histiocytosis-X in the posterior lobe of the pituitary gland (Gagel's granuloma) is presented. The thoracic, retroperitoneal and pituitary lesions were characterized by a histiocytic proliferation with extensive reticulin and collagen production. Electron microscopy of the cellular areas of the mediastinal and retroperitoneal process confirmed the histiocytic nature of the lesion and revealed intracytoplasmic filaments resembling Langerhans' cell granules. These features together with the pituitary lesion in this case suggest that the mediastinal and retroperitoneal sclerosing process may be a form of histiocytosis-X.