title: Pseudo-tumours, a clinical concept.
abstract: Space-filling lesions in the orbit can be divided into 3 large groups: 1. Acute and subacute inflammatory processes (bacterial, fungal, parasitic, foreign body). 2. Benign and malignant tumours, true new growths. 3. Pseudo-tumours. The conditions in group 3 are also space-filling lesions, but have the characteristics of a chronic, infiltrating, inflammatory process. In 11% of 340 consecutive patients in the Orbital Centre in Amsterdam this diagnosis was made. The group is far from uniform: the dominant cell type varies from one case to another. Usually lymphocytic cells are dominant; if these are arranged in follicles the lesion is called a pseudo-lymphoma. This condition can gradually leave the province of the pseudo-tumours and begin to show the characteristics of a malignant or non-Hodgkin lymphoma. Sometimes the inflammatory character of the lymphoid infiltration is dominant, as in myositis, sclerotenonitis and infiltrative Graves' ophthalmopathy; these conditions are clearly related to immunological processes. Attempts to classify all pseudo-tumours on a pathological basis have remained rather vague.
  
  
  METHODS
  rapid development (2-6 months); pain and oedema are present, but these are not the principal symptoms; secondary features are: disorders of motility, visual loss and other symptoms. Bilaterality usually indicates the presence of a systemic disease.
mesh_terms: D003240:Connective Tissue Diseases / Q000473:pathology; D005350:Fibroma / Q000175:diagnosis*; D006111:Graves Disease / Q000473:pathology; D006801:Humans; D008223:Lymphoma / Q000473:pathology; D009220:Myositis / Q000473:pathology; D009916:Orbital Diseases / Q000175:diagnosis* / Q000473:pathology; D009918:Orbital Neoplasms / Q000175:diagnosis*