In medicine,<unk>  is an excessive number of histiocytes,that is an excessive number of tissue macrophages, and is typically used to refer to a group of rare diseases which share this as a characteristic.  Occasionally and confusingly it is sometimes used to refer to individual diseases.<unk>  (and malignant<unk>  are both important in veterinary as well as human pathology.
Histiocytosis
Pulmonary amyloidosis
Non-Hodgkin lymphoma
Angiolymphoid hyperplasia with eosinophilia
B-cell lymphoma
Lymphomatoid granulomatosis
Tuberculosis
Sarcoidosis