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.