Recently, probe based confocal laser endomicroscopy showed to be able to distinguish malignant from benign pleura during medical thoracoscopy. However The clinical usefulness of this new tool remains to be determined.

The investigators believe that pCLE could be part of mini invasive pleural disease management and could be used during thoracentesis in order to increase the diagnostic yield of this procedure. The investigators are starting a prospective trial to recruit patients referred for medical thoracoscopy to the endoscopy unit.

First, the pCLE probe will be introduced through the Boutin's needle or the thoracentesis catheter, just before the thoracoscopy, in order to investigate the pleural pCLE features and to identify or exclude malignant infiltration. Second those features will be compared to the pCLE acquisition obtained during the medical thoracoscopy (the probe is introduced through the working chanel of the thoracoscope), under visual control. In order to compare the invasive and mini invasive acquisition, 10 criteria will be prospectively assessed.Third, These features will be compared to the histological samples performed during thoracoscopy. Finally, the interpretation of different investigators will be compared.

The 10 criteria are presented below:

1. Abnormal tissular architecture

   No: Correct identification of the previously described normal pleura characteristics Yes: identification of cellular/tissular structures which are not known to correspond to normal pleura (cellular clusters or dark clumps, glands, cells cordons, dysmorphic cells, papillar distribution….)

2. Cellular homogeneity is size, shape and fluorescence, as subjectively assessed by the investigator

   yes no

3. Mean cellular size:

   Small: < 10µm Moderate: 10 - 20µm Large: > 20µm

4. Cellular density (with reference to the Chia seed sign)

   Low (lower than the Chia seed sign) Moderate High

5. Dysplastic vessels:

   Yes: (vascular leaks, tortuous or giant vessels) No: no dysplasia

6. Vascular density (on a full optical area)

   Low: 0 -2 vessels Moderate: 3 - 4 vessels High: > 4 vessels

7. Organized or anarchic connective fibers

   Anarchic: coarse fibers, irregular in shape, without well-defined architecture Organized : regular in shape and direction, well defined architecture.

8. Chia seed sign on a full optical areal

yes No

Inclusion Criteria:

• Every patient referred to the endoscopy unit for medical thoracoscopy

Exclusion Criteria:

• Pregnancy
• Known allergy to the fluorescein

Every patient referred to the endoscopy unit for medical thoracoscopy

One day