OVERVIEW OF PRIMARY MEDIASTINAL TUMORS AND CYST

GENERAL THORACIC SURGERY

CHAPTER 160

Mediastinal tumor

• Numerous tumor and cyst occurred in mediastinum.

• Affect all age. • More common in young and middle-age adult. • Most mass are discovered on routine radiographic

examination. • Benign lesion most asymptomatic, malignant

lesion most produce clinical finding.

Mediastinal component

• Anterior compartment.

• Visceral compartment.

• Paravertebral sulci.

Location of common tumor and cyst

• Anterior mediastinum – Thymoma, lymphoma, germ cell tumor.

• Visceral compartment – Fore-gut cyst, bronchogenic cyst, esophageal, and gastric origin, secondary tumor of lymph node, pleuropericardial cyst, cystic lymphangioma.

• Paravertebral sulci – Neurogenic tumor, vascular tumor, mesenchymal tumor, lymphatic lesion, fibroma, lipoma.

Signs and symptoms

• child—2/3 with symptoms

• Adult 1/3 with symptoms.

• Symptom /sign dependent on benign and malignant, size, location, infection, endocrine or biochemical products.

Signs and symptoms

• Infant and child — Cough, dyspnea stridor are prominent even a small mass, septic complication with resultant pneumonitis, fever frequently.

• Adult — cough dyspnea, chest pain, s/s related infection, obstruction vital structure, invasion adjacent structure, pleural effusion, Horner’s syndrome, diaphragm paralysis.

Benignity versus malignancy

• Adult — Less 40% of anterior mediastinal tumor are malignant, almost all cyst are benign.

• Child — Incident of malignancy is high than adult, most malignant tumor are in child less than 3 y/o （ 86% ） , 91% benign lesion in older children, 45% lesion in child anterior compartment are malignant lymphoma.

Benignity versus malignancy

• Only small percentage of germ cell tumor in child are malignant.

• In visceral compartment —Mmany lymph node lesion are malignant.

DIAGNOSTIC INVESTIGATION OF MEDIASTINAL MASSES

GENERAL THORACIC SURGERY

CHAPTER 161

Noninvasive diagnostic procedures

• CT

• MRI

• Ultrasonography

• Radionuclide scanning

• Biochemical markers

CT• Routine. • More detail, invasion into adjacent structure pleural

or lung parenchymal metastases. • Sensitive method of distinguishing between fatty,

vascular, cystic, soft tissue mass. • Differentiation in solid and cystic mass– 100%. • Solid mass-- homogeneity or inhomogeneity. • Contrast enhancement of vessel.• Cannot differentiate between benign and malignant

tumor.

MRI

• Additional useful information in separation mediastinal tumor from vessels and bronchi.

• Superior to CT in evaluation intraspinal extention or intrathecal spread of paravertebral mass.

Ultrasonography

• -- Differentiation in solid and cystic.

Radionuclide scanning

• Thyroid – I131, I123. • Parathyroid – Tc 99m. • Octreotide – Somatostatin analogue, identifiy

small cell carcinoid tumors of lung. • Tc-99m–pertechnate scan – identified gastric

mucosa in suspected neuroenteric cyst in posterior portion of visceral compartment.

• Gallium 67 – differentiate benign from malignant anterior mediastinal mass.

Biochemical markers

• α-fetoprotein, β-human chorionic gonadotropin(β –HCG), ether one or both elevated in nonseminomatous malignant germ cell tumor.

• Excess than 500 ng/ml, can start chemotherapy without a tissue biopsy.

• 7-10% pure seminoma may elevated β- HCG but nor exceed 100 ng/ml, but elevated α-fetoprotein is never present.

Biochemical markers

• All infant and children with paravertebral mass should evaluated for excessive norepinephrine and epinephrine production.

• Ferritin level – for neuroblastoma.• Antiacetylcholine receptor antibodies–

thymoma.• Positron emission tomographic scanning –

Differentiating a noninvasive thymoma.

Invasive biopsy procedure

• Choice of invasive diagnostic procedures depends on

Presence or absence of local symptoms.

Location and extent of lesion.

Presence or absence various tumor marker.

Invasive biopsy procedure

• Do not require tissue biopsy before removal

Asymptomatic lesion without systemic

syndrome.

Confined in anterior compartment.

No elevating tumor marker.

• Biopsy of clinical stage I thymoma is to be avoid.

Percutaneous transthoracic fine-needle aspiration

• —CT or sono-guide. • Anterior compartment lesion—positive result

nearly 100%. • Complication is life-threating hemorrhage form

injury internal mammary artery during parasternal needle biopsy.

• CT-guide is much better. • Coaxial length-matched bone biopsy system guide

by CT.

Percutaneous transthoracic fine-needle aspiration

• Visceral compartment—transthoracically with passage of needle through lung.

• Success rate 75%.

• Complication pneumothorax is low.

• Paravertebral mass—CT-guide biopsy 100% success rate.

Mediastinoscopy

• Anterior mediastinal tumor, the mediastinoscopy is NOT appropriate for biopsy – May be obtain by cervical substernal extended mediastinotomy or anterior mediastinotomy.

• Lymph node confined to visceral compartment, biopsy via a standard cervical mediastinoscopy is used.