Mesothelioma

A. Benign Pleural Fibroma:

-Pathology:

· Age: 40 years (but children are reported too)

· Size: small discovered accidentally à large & producing symptoms

· Shape: spherical, lobulated, well encapsulated, surrounded by compressed lung tissue

· Site: from any site in the pleural surface (visceral or parietal), connected to the pleura with a pedicle or broad base

· L/M: interlaced fibrous tissue + myxomatous degeneration + mesothelial cells or sub-mesothelial mesenchymal cells (pleomorphism with few mitotic cells)

-Clinical Picture:

.Symptoms:

· Asymptomatic

· General: fever, chills, hypoglycemia, clubbing up to osteoarthropathy (all are reversible after surgery).

· Local: symptoms of pressure à progressive dyspnea or pleuritic chest pain

.Signs:

· May mimic pleural effusion à displace mediastinum

· May mimic pericarditis (constrictive type) due to gross mediastinal displacement

-Behavior:

· Simple for a long time

· Invasive (especially after surgical resection) à Anaplastic Fibrosarcoma

· Recurrence (suspected with return of constitutional symptoms)

-Investigations:

1. CXR: appears as a dense homogenous, spherical and lobulated opacity anywhere in the pleura (if in fissure appears ovoid) ± seen with a connection to the pleura by a pedicle or broad base.

2. Biopsy: see pathology.

-Treatment:

Surgical resection as it's a potentially malignant disease (no lung tissue removed).

B. Malignant Mesothelioma:

-Definition:

It's a cancerous proliferation of mesothelial cells that usually involves a large extent of the pleural cavity.

-Etiology:

· Asbestos exposure (major risk factor of 80%) à occurs with crocidolite more with latent period of 30-45 yrs.

· Erionite fiber mineral exposure (more in Turkey).

· Chest wall irradiation (very rare non-industrial cause).

-Pathology:

Mixed	Sarcomatous	Epithelial (Tubulopapillary)	Undifferentiated polygonal type
1 :	1 :	2	----
Easiest to diagnose as it's a metastasis from a tumor with histological elements (LN, Bone …etc)	Cellular fibro-sarcoma with myxoma & acellular collagen	Similar to 2ry adenocarcinoma with regularly ordered cells ± dust or carbon, nuclei are vesicular with no mitosis, dilated acini appears as branching fronels lined with cuboidal cells	Sheets of polygonal or solid epithelial cells
Asbestos bodies seen in the underlying lung tissue supports the diagnosis

-Staging:

Stage I: Ipsilateral only à lung, parietal pleura, pericardium, diaphragm.

Stage II: Local invasion à chest wall, heart, LNs & esophagus.

Stage III: Penetrates diaphragm à peritoneum, opposite pleura, LNs out.

Stage IV: Distant metastasis.

-Clinical Picture:

.General: cachexia, fever, rarely clubbing & rarely LN⁺⁺

.Local: Signs of pleural effusion + frozen mediastinum (more) or shift to the contralateral side (rare with massive effusion) à shift of the mediastinum to the same side (with marked pleural encasement).

-D.D.:

1. Metastatic adenocarcinoma: differentiated by immuno-histochemistry, CEA, B₁ specific glycoprotein.

2. Benign asbestos pleural effusion: occurs in the 1^st 20 yrs of exposure, small, asymptomatic and needs only follow-up.

3. Benign fibrous mesothelioma (pleural fibroma): see before.

4. Pleural thickening or fibrosis: see later.

-Investigations:

1. Radiology:

a) CXR:

· Large pleural effusion: earliest picture (absent in 20% of cases, can be bilateral in < 5%).

· Pleural thickening: irregular pleura.

· Pleural nodules: unilateral.

· Asbestos related plaques, calcifications, & parenchymal fibrosis.

· Spread later: pericardial effusion, mediastinal widening, and rib destruction.

b) CT chest:

· Pleural nodular thickening and encasement later.

· Pleural effusions.

· Pleuro-pulmonary changes in the opposite hemithorax.

· Evidence of local spread.

2. Functions:

a) Spirometry: progressive restrictive pattern

b) ABG: normal up to respiratory failure

3. Thoracocentesis:

a) Chemical:

· Exaudative

· Low PH

· Low glucose

· High hyaluronic acid concentration (viscid fluid).

b) Physical: straw colored, sero-sanguinous or hgic fluid.

c) Cytological: +ve for malignancy in 10% of cases.

4. Biopsy:

a) Closed: by Abram's needle (non-diagnostic small insufficient)

b) Open: diagnostic

c) VATS: useful early

-Treatment:

-Curative treatment: None

-Palliative treatment:

· Surgery (with high mortality rate so it's not done): extrapleural pneumonectomy, pleurectomy & decortication, limited pleurectomy, or thoracoscopy with talc powdrage.

· Radiotherapy: with some regression and lowering fluid accumulation.

· Chemotherapy (single agent): Adriamycin or Cyclophosphamide.

· Analgesics, palliative thoracocentesis & pleuredesis, O₂ & prednisolone (decreases fever and sweating).

*Pleural Thickening or Fibrosis:

-Definition:

It's a diffuse process involving parietal and visceral layers of pleura with infrequent involvement of the surface of the lung.

-Etiology:

.Localized type: as a sequence of exaudative pleural effusion of any cause

.Generalized type:

Unilateral	Bilateral
-TB effusion -Old artificial pneumothorax -Hemo-thorax -Empyema	-Asbestosis -Rheumatoid disease -SLE -Drugs (methyrgide, proctalol)
With Calcification	Non Calcified except asbestosis

-Clinical Picture:

· History of pleural effusion, asbestos exposure.

· Asymptomatic à if unilateral with no lung disease.

· Exertional dyspnea à if extensive bilateral.

· Chest pain (v rare) à suspect tumor not fibrosis.

-Investigations:

1. CXR:

· Localized thickness in the lower zone with obliteration of CP-angle.

· Streaky irregular infiltrations.

· Diffuse thickening.

· Thickening + nodular picture à suspect cancer or mesothelioma

· Atelectasis can be found.

· Calcifications can be seen.

2. CT chest: Done when:

· Mesothelioma is suspected.

· See if there is an underlying lung disease.

· Before surgery.

3. PFT:

· Restrictive pattern

· Normal DLCo

· Low Compliance

-D.D.: from malignant infiltration of mesothelioma.

-Treatment:

.Of the cause

.Pleurectomy & decortication:

· In localized type: only if there is restriction

· In diffuse type: with pre-operative assessment of underlying lung disease, persistent disability, hazards of the procedure & lung functions.

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