What the findings suggest?
Left lower lobe collapse, and mediastinal lymphadenopathy.
Why is there not a typical triangular opacity in the left lower region on the lateral view?
Because there is a mass in the lower pole of the left hilum extending the opacity.
There is one more thing we can spot on the PA view. Which one?
Blunting of the left costophrenic angle.
What is the most frequent cause of such findings?
Triangular left paravertebral opacity with a double cardiac contour. Left shift of the mediastinum. Blunting of the left costophrenic angle.