Up to 85% of cases of SVCS are caused by malignancy. It is especially common in association with bronchogenic carcinoma, which accounts for 75% of cases, and in lymphoma. Central intravenous lines are the second most common cause. Most patients respond rapidly to treatment, and early diagnosis is important.

The SVCS results when tumor growth in the mediastinum compresses the superior vena cava. This leads to venous hypertension in the head, neck, and upper extremities. Signs and symptoms are promptly relieved when treatment decompresses the superior vena cava. If thrombosis of the vena cava occurs, there is a poor prognosis.

The most common symptoms of the SVCS are dyspnea (50% of patients) and swelling of the face and upper extremities (40%). Less common symptoms are cough, dysphagia, headache, chest pain, blurred vision, and altered mental status. Early signs include
periorbital edema and conjunctival injection. Later, the full-blown syndrome including thoracic and neck vein distention, facial edema with plethora or cyanosis, and edema of the upper extremities may develop. If left untreated, extrinsic vena cava compression may lead to irreversible thrombosis. This occurs in 10% to 20% of cases. Death may occur from intracranial propagation of the thrombus or from tracheal compression.

The differential diagnosis is relatively short and includes nephrotic syndrome, pericardial tamponade, and congestive heart failure. These can be differentiated by physical examination and basic ancillary testing.

Useful diagnostic tests include the chest x-ray and computed tomography (CT) scan of the thorax. Chest x-ray reveals a mass in almost all cases. There is often associated adenopathy, pulmonary parenchymal lesions, or effusion. The CT scan can provide detailed anatomic information about the location and extent of the obstruction. Upper extremity venous access should be avoided. Venous hypertension and low flow rates predispose to bleeding and thrombotic complications. Contrast venography is therefore also contraindicated. If venous access is necessary, it may be obtained through the lower extremity.

The primary treatment of SVCS is radiation therapy to the mediastinum. Seventy to eighty percent of treated patients will have a good symptomatic response within a week. Patients with lymphoma have the best response. Poor responders often have thrombosis of the superior vena cava. Chemotherapy is also used as a primary treatment modality in selected cases. The simple measure of elevating the head and upper body may provide significant relief of symptoms.

The prognosis for patients with SVCS depends on the underlying malignancy. Patients with lymphoma have better survival than those with bronchogenic carcinoma. The overall survival for all patients with SVCS is 25% at 1 year. Despite this poor prognosis, not all patients with the diagnosis of SVCS in the emergency department require admission. When the signs and symptoms are not severe and the underlying malignancy is known, reliable patients with access to timely and appropriate follow-up may be discharged. Patients who lack these characteristics require admission.

Hypercalcemia is the most common metabolic emergency associated with malignancy. It is reported in up to 25% of cancer patients. Most cases are related to solid tumors, with lung (especially squamous cell carcinoma) and breast cancer being the most common. Many other solid tumors as well as leukemia and lymphoma have also been associated with hypercalcemia. The mechanisms by which malignancy causes hypercalcemia may include increased bone resorption at the site of metastases or increased osteoclastic resorption at sites distant from the tumor. The latter effect is mediated by tumor-secreted hormone-like substances. Hypercalcemia may therefore occur in the absence of disseminated malignancy.