Differential diagnosis between sarcomatoid-type mesothelioma vs squamous cell carcinoma or sarcoma

Differential diagnosis between sarcomatoid-type mesothelioma vs squamous cell carcinoma or sarcoma

It is recommended to use (grade 1A):

2 anti-cytokeratins and calretinin

and at least 2 markers of negative predictive value whose constitution is to be discussed according to the morphological presentation (CD34, desmin, PS 100, Bcl2, CD 99, HBM45, STAT6, ...)

Sarcomatoid mesotheliomas express cytokeratin and vimentin, more inconstantly desmin and actin; and CD 34 is negative (unlike other pleural fibrous tumors).

A negative test with a single antibody does not exclude the diagnosis (grade 1C).

3.5.3. Atypical mesothelial hyperplasia

There is no currently marketed immunohistochemical marker that differentiates benign and malignant cells.

In difficult cases, the demonstration of a homozygous deletion of the CDKNZA (p16) gene (FISH) is an important argument in favor of mesothelioma. Likewise, the loss of expression of BAP1 (IHC) appears very specific in confirming the diagnosis of malignant mesothelioma.

3.6. Electron microscopy and molecular biology

Microscopy and molecular biology are not recommended for the diagnosis of mesothelioma (grade 1A).

 

There is no diagnostic or therapeutic reason to freeze tumor pleural tissue outside of a trial (grade 1A).

3.7. Panel of experts

An independent panel of anatomo-pathologists must confirm the diagnosis of mesothelioma (recommendation, grade 1B).

It is available to analyze files within the framework of the National Mesothelioma Surveillance Program (PNSM) (Institut de Veille Sanitaire) and the National Referral Center for Malignant Pleural Mesotheliomas and Rare Peritoneal Tumors (INCa).

The diagnostic validation procedure by the national expert group (MESOPATH group) is optional, left to the discretion of the pathologist, if the patient is not included in the PNSM.

On the other hand, it is compulsory if the patient is included in the PNSM: send to the regional referee (see below) of the PNSM a paraffin block or a minimum of ten white slides, keeping the material locally for possible future use.

 

The pathologist referent, regardless of his function as consultant:

1- ensures the realization of the immunohistochemical panel,

2- includes the observations in the national file of mesotheliomas located at the Léon Bérard Center in Lyon

3- participates in the diagnostic validation as an expert of the MESOPATH group during the latter's meetings.

 

Contact details of referees

for the East region:

Prof. J.M. Vignaud

Pathological anatomy laboratory

CHRU - Central Hospital

29, avenue du Maréchal de Lattre de Tassigny, CO n ° 34

54035 NANCY Cedex

 

for the MESOPATH group:

Pr F. Galateau-Salle / Pr S. Lantuejoul

Pathological anatomy laboratory

Léon Bérard Cancer Center

28 rue Laennec

69373 LYON

4. Classification

The classification describes the anatomical extent of the tumor. There are 5 classification systems that can be used in mesothelioma. An international panel of experts could not agree on a common classification and called for the creation of a new uniform classification including the histological TNM classification.

 

In the absence of a uniform, robust and validated classification, the experts recommend using the most recent TNM classification (grade 1C) which is the 8th edition of the UICC TNM classification of cancers (2017), below. below.

4.1. 8th edition of the UICC TNM classification of cancers (2017)

T - Tumor

T1 Tumor limited to the parietal or visceral or ipsilateral mediastinal pleura.

T2 Tumor of the parietal or visceral pleura ipsilateral, with at least one of the following characteristics:

diaphragmatic muscle damage,

damage to the pulmonary parenchyma.

T3 Locally advanced but potentially resectable tumor: tumor of the parietal or ipsilateral visceral pleura, with at least one of the following characteristics:

endothoracic fascia damage,

extension to mediastinal fat,

isolated nodular extension, resectable to the chest wall, with or without costal destruction,

non-trans-mural pericardial involvement.

T4 Locally advanced unresectable tumor: tumor of the parietal or ipsilateral visceral pleura, with at least one of the following characteristics:

diffuse or multifocal damage to the chest wall with or without costal destruction,

trans-diaphragmatic damage to the peritoneum,

direct extension to the controlateral pleura,

direct extension to the mediastinal organs, to the spine, to the internal surface of the pericardium, to the myocardium.

N - Lymphadenopathy

Nx Unknown loco-regional invasion.

N0 No lymph node involvement.

N1 ipsilateral thoracic lymph node involvement.

N2 Involvement of the contralateral thoracic lymph nodes or the homo or contralateral supraclavicular lymph nodes.

M - Metastases

M0 No metastases