Thinking Through Pathology
The lesions of interstitial lung diseases populate the framework of the secondary lobule. These are polygonal structures, 1–2 cm in diameter, bound by complete or incomplete connective tissue (interlobular septa), well visible on the pleural surface as th
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Introduction and anatomy Elementary lesions
How to approach the diseases
Alessandra Cancellieri Alberto Cavazza Giorgia Dalpiaz
Secondary lobule Defining lesions: neoplasm Defining lesions: mixture Non-defining lesions: inflammation Non-defining lesions: fibrosis Anatomic distribution Patterns Ancillary histologic findings
© Springer International Publishing Switzerland 2017 G. Dalpiaz, A. Cancellieri (eds.), Atlas of Diffuse Lung Diseases, DOI 10.1007/978-3-319-42752-2_2
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Thinking Through Pathology
Thinking Through Pathology
Introduction and Anatomy
Dalpiaz & Cancellieri
SECONDARY LOBULE The lesions of interstitial lung diseases populate the framework of the secondary lobule. These are polygonal structures, 1–2 cm in diameter, bound by complete or incomplete connective tissue (interlobular septa), well visible on the pleural surface as thin anthracotic lines due to the deposition of pigment along the lymphatic routes.
In the above figures, interlobular septa are particularly well recognizable because of the black anthracotic material along the perilobular lymphatics. Both on the pleura (A) and on the cut surface (B).
Main Components of Secondary Lobule
The main components of secondary lobule are: • Bronchioles and arterioles constitute the bronchovascular bundle in the center of the lobule ( ). Bronchioles and arterioles come along together following the same routes. • Venules, on the contrary, can be found peripherally, in the interlobular septa and along the pleura (►). • Lymphatics, of variable caliber but usually smaller than bronchioles and arterioles, are present in all the above-mentioned compartments (i.e., bronchovascular bundle, interlobular septa, and pleura).
Rule of thumb: no matter how they are cut, bronchioles and arterioles should have approximately comparable size (and – therefore – lumen diameter) and, often, shape. When arterioles and bronchioles are of different caliber, something is abnormal.
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Atlas of Diffuse Lung Diseases
Introduction and Anatomy
Dalpiaz & Cancellieri
Intralobular Interstitium/ Septa
Within the lobule, a fine stromal network of intralobular septa make up the framework of the acini and, more specifically, of the anatomical units responsible for gas exchange: respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli. The intralobular (alveolar) septa contain the smallest branches of arterioles and venules, as well as the capillary network. Figure A below shows normal intralobular septa. Figure B shows normal intralobular septa (¨) and thickened septa due to “lepidic growth” (►) in a patient with adenocarcinoma.
A
HRCT
B
On HRCT, secondary lobules appear to be of various sizes and shapes, depending at least partially on the relationship of the lobule to the plane of scan. They may be thought of as having three primary components: • Interlobular septa and septal structures (Figure A below). At the periphery of lobule, the interlobular septa are arranged more or less regularly, pa
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