Other Malignant Tumors of the Esophagus

SITES OF ORIGIN

Esophageal metastases are found at autopsy in less than 5% of patients dying of cancer. Carcinoma of the gastric cardia or fundus often invades the distal esophagus, accounting for about 50% of these metastases. Less commonly, lung and breast cancer involve the esophagus by extension of lymphadenopathy or metastatic tumor from the adjacent mediastinum. The esophagus may also be directly invaded by laryngeal, pharyngeal, and thyroid carcinomas in the neck. Rarely, the esophagus may even be involved by hematogenous metastases from cancers arising in distant structures.

CLINICAL FINDINGS

Patients with esophageal metastases may present with dysphagia because of luminal narrowing by metastatic tumor, and they usually have a poor prognosis because of widespread metastatic disease. ^, In patients with breast cancer, late-onset esophageal metastases may cause dysphagia many years after diagnosis of the original cancer.

RADIOGRAPHIC FINDINGS

Direct Invasion

Direct invasion of the esophagus by laryngeal, pharyngeal, thyroid, or lung cancer produces characteristic findings on barium studies. Early involvement is usually manifested by a smooth, gently sloping indentation on the esophagus, but the contour of the involved segment becomes serrated, scalloped, nodular, or ulcerated as the wall is further infiltrated by tumor ( Fig. 13.1 ). Eventually, circumferential esophageal invasion causes irregular luminal narrowing and/or obstruction ( Fig. 13.2 ). Rarely, thyroid cancer invading the esophagus appears as an expansile intraluminal mass, mimicking spindle cell carcinoma (see later, “Spindle Cell Carcinoma”).

Esophageal involvement by carcinoma of the gastric cardia or fundus may be manifested on barium studies by tumor in the fundus extending into the distal esophagus as a polypoid mass ( Fig. 13.3 ) or as an infiltrating lesion with irregular luminal narrowing. ^, Occasionally, these tumors may cause smooth, tapered narrowing of the distal esophagus, mimicking achalasia (see later, “Secondary Achalasia”).

When the distal esophagus is involved by carcinoma of the gastric cardia or fundus, barium studies often reveal the underlying gastric tumor as a polypoid, ulcerated, or infiltrating lesion in the fundus by (see Fig. 13.3B ). In other cases, double-contrast studies show distortion or obliteration of the normal landmarks at the cardia with nodularity, mass effect, or ulceration in this region ( Fig. 13.4 ). ^,

Contiguous Involvement by Mediastinal Lymph Nodes

Lung and breast cancer are the most common malignant tumors that metastasize to mediastinal lymph nodes involving the esophagus. Mediastinal lymphadenopathy typically involves the midesophagus because of its proximity to subcarinal lymph nodes. Barium studies usually reveal a smooth or slightly lobulated indentation at or just below the carina ( Fig. 13.5A ). The esophagus may have an irregular, nodular, or ulcerated contour when it is directly invaded by tumor-containing lymph nodes ( Fig. 13.6 ). ^{, ,} Eventually, there may be concentric esophageal narrowing when it is circumferentially infiltrated by tumor ( Fig. 13.7 ). ^{, ,} In such cases, computed tomography (CT) should be performed to show the full extent of adenopathy in the mediastinum ( Fig. 13.5B ).

Hematogenous Metastases

Blood-borne or hematogenous metastases to the esophagus are extremely uncommon. Most patients have underlying breast cancer, but other distant tumors occasionally metastasize hematogenously to the esophagus. Surprisingly, malignant melanoma, which has the highest percentage of blood-borne metastases to the gastrointestinal (GI) tract, rarely involves the esophagus. Blood-borne esophageal metastases usually appear on barium studies as short, eccentric midesophageal strictures with smooth contours and tapered margins ( Fig. 13.8 ). ^{, , ,}

DIFFERENTIAL DIAGNOSIS

A smooth indentation on the esophagus on barium studies may be caused by other extrinsic lesions, including benign mediastinal tumors and cysts, aberrant vessels, and an ectatic aorta or aortic aneurysm. In contrast, esophageal invasion by metastatic tumor should be suspected when the involved segment has an irregular, serrated, nodular, or ulcerated contour.

The differential diagnosis for upper or midesophageal strictures caused by metastatic tumor includes Barrett’s esophagus and scarring from mediastinal irradiation, caustic ingestion, eosinophilic esophagitis, lichen planus, or oral medications such as potassium chloride, but these benign strictures usually have a smooth contour and more tapered margins. When patients are known to have undergone radiation therapy for an intrathoracic cancer, the major considerations include a benign radiation stricture and recurrent tumor. In such cases, CT may confirm the presence of tumor by showing a mass or lymphadenopathy in the adjacent mediastinum.

PATHOGENESIS

Primary and secondary achalasia are characterized by absent esophageal peristalsis and a hypertensive lower esophageal sphincter that fails to relax normally in response to deglutition. In patients with primary achalasia, the motor disorder is caused by degeneration and loss of the ganglion cells of Auerbach’s plexus. In contrast, the pathogenesis of secondary achalasia is multifactorial. Some patients have destruction of myenteric ganglia by tumor in the distal esophagus. In others, however, secondary achalasia may be caused by extraesophageal metastases to the vagus nerve or dorsal motor nucleus in the brain stem. ^, Secondary achalasia may also occur as a paraneoplastic phenomenon caused by circulating tumor products. Finally, malignant neuroendocrine tumors (particularly small cell lung cancer) can express neural antigens that initiate an autoimmune response with circulating antibodies—known as anti-Hu antibodies—that cause secondary achalasia.

CLINICAL FINDINGS

The clinical history is important for differentiating primary and secondary achalasia. Most patients with primary achalasia are between 20 and 50 years of age and have dysphagia for a mean duration of 4 to 6 years before seeking medical attention. ^, In contrast, most patients with secondary achalasia are over 60 years of age and have dysphagia for less than 6 months. ^, Secondary achalasia also is far more likely to be associated with weight loss. An underlying malignant tumor should therefore be suspected when achalasia is diagnosed in older patients with recent onset of dysphagia and weight loss. Nevertheless, some patients with primary achalasia are over 60 years of age and others have a short duration of symptoms, ^{, ,} so it is not always possible to differentiate these conditions on clinical grounds.