Simon focus

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A Simon focus is a tuberculosis (TB) nodule that can form in the apex of the lung when a primary TB infection elsewhere in the body spreads to the lung apex via the bloodstream.[1] Simon focus nodules are often calcified.[1]

• The initial lesion is usually a small focus of consolidation, less than 2cm in diameter and located within 1 to 2 cm of the apical pleura.[2] • In adolescence, Simon foci may get reactivated to become Assmann foci. Such foci are sharply circumscribed, firm, gray-white to yellow areas that have a variable amount of central caseation & peripheral fibrosis.


  1. ^ a b Leung, AN (February 1999). "Pulmonary tuberculosis: the essentials.". Radiology 210 (2): 307–22. doi:10.1148/radiology.210.2.r99ja34307. PMID 10207408. 
  2. ^ Robbins, 8th edition