Simon focus

From Wikipedia, the free encyclopedia
Jump to: navigation, search

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 become reactivated and develop into Assmann foci.[3] Such foci are sharply circumscribed, firm, gray-white to yellow areas that have a variable amount of central caseation and 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 Basic Pathology (8th edition). Elsevier. 2007. ISBN 978-1-4160-2973-1. 
  3. ^ "Assmann focus". Retrieved 4 March 2015.