Characters of mediastinal cysts

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If you see a cyst with the most of its parenchyma seen in the lung area while a small part of it is seen in the mediastinum, diagnose it as a mediastinal lesion and not as lung lesion, as it is very difficult to a lung cyst(benign and soft) to deviate into mediastinum, but it is very easy to a mediastinal cyst to merge from mediastinum to the lung area(this rule is not a  typical in case of bronchogenic carcinoma).