Pseudo-tumours, a clinical concept.

UNLABELLED: 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.

CLINICAL PICTURE: 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.