Metastatic gastroesophageal adenocarcinoma to skeletal muscle: a unique event.

ABSTRACT

Skeletal muscle is rarely the site of metastatic cancer, though a few such cases have been reported. Esophageal adenocarcinoma metastasic to skeletal muscle has not previously been reported in the literature. We describe the case of 71-year-old African American male with stage IV adenocarcinoma of the gastroesophageal junction. He had severe and disabling pain in the right thigh, which was tender to palpation. The pain was unresponsive to nonsteroidal anti-inflammatory drugs and full-dose narcotics. Plain x-ray films and bone scan were nondiagnostic. Magnetic resonance imaging showed a soft tissue mass involving the thigh muscles, anterior and medial to the right femur. Computed tomography (CT)-guided biopsy revealed that the thigh mass was metastatic adenocarcinoma consistent with the primary gastroesophageal cancer. Metastasis to muscle is rare, but physicians should be aware of the possibility because detection requires specific tests. We discuss the role of these tests, as well as available trea tment options.

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ALTHOUGH SKELETAL MUSCLE comprises 50% of body mass and has a rich blood supply, it is rarely the site of metastatic disease; only 242 cases have previously been reported. (1) Primary cancers of the lung, colon, genitourinary tract, and blood are most frequently involved, (1,2) but gastroesophageal adenocarcinoma metastatic to skeletal muscle has never been reported. We report a case of thigh muscle metastasis from primary adenocarcinoma of the gastroesophageal junction.

CASE REPORT

A 71-year-old African American man had severe right thigh pain that caused him to be unable to walk. His medical diagnoses included stage IV adenocarcinoma of the gastroesophageal junction, hypertension, chronic obstructive pulmonary disease (COPD), and gastroesophageal reflux disease (GERD). He was an active smoker and formerly a heavy drinker. Physical examination was remarkable only for his cachectic state and his extremely tender right upper thigh. Despite nonsteroidal anti-inflammatory drugs (NSAIDs) and full-dose narcotic analgesia, the patient continued to have severe pain in his thigh. X-ray films showed no lytic or blastic lesions in the thigh, nor did the bone scan show any metastases. Magnetic resonance imaging (MRI) showed a deep soft tissue muscle mass measuring 2 x 4 cm in the right thigh, just anterior and medial to the femur without bone involvement. Diagnostic considerations included a soft tissue metastasis or a sarcoma. A CT-guided needle biopsy of the right thigh mass was positive for meta static adenocarcinoma consistent with the primary esophageal cancer.

The patient was treated with radiation therapy to the right thigh and had a good response. At the time of discharge, he was receiving narcotic analgesia and walking without pain. He continued radiation therapy as an outpatient and was still walking without difficulty when he returned to the clinic for follow-up 2 weeks later.

DISCUSSION

The incidence of adenocarcinoma of the esophagus and gastroesophageal junction has been increasing over the past 25 years, (3-6) with cancer of the esophagus, which previously had been predominantly squamous cell carcinoma, ranking among the 10 most frequent cancers in the world.

Although direct muscle invasion by carcinoma is well recognized, distant metastasis to skeletal muscle is uncommon. (7) The present case is unique in that the localized thigh pain was produced by metastatic involvement of the thigh musculature without any osseous or perineural lymphatic extension.

Even though autopsy series report a 0.8% to 20.0% incidence of microscopic intramuscular metastases, (8-12) only a few cases of visible metastases to the muscle have been described in the literature. (13-17) Muscle metastasis often remains asymptomatic, undetected by either physical examination or diagnostic imaging procedures. The reported incidence, therefore, might be rare because of a lack of recognition, underreporting, or infrequent autopsy evaluation for muscle metastasis. (17) Furthermore, it may be that only a fraction of patients with metastases to muscle survive long enough to allow clinical detection. (18)

The reason why metastases to skeletal muscle are so rare is still unknown. (28,19) Multiple factors, such as blood flow, intramuscular blood pressure, blood flow per unit of weight (mL/min/g), local changes in pH, as well as local temperature distribution may be involved. (7,9,11,20-23) Organs with a high incidence of metastatic carcinoma such as lung, liver, and bone have a constant blood flow. Although skeletal muscle is equally rich in its vasculature, it has been suggested that its blood flow is variable, under the influence of [beta] adrenergic receptor control, and subject to varying tissue pressure that may affect tumor implantation. (21,24) Although some have suggested that protease inhibitors in the extracellular matrix of the muscle may resist tumor cell invasion, (25) it may be the production of lactic acid and other metabolites by skeletal muscle that inhibits tumor cell growth. (19,21)

Two thirds of all cancers metastatic to muscle are carcinomas, about one third are from leukemias and lymphomas, and rare cases originate from melanomas (26); therefore, although factors in the recipient site may be responsible for the relatively low rates of metastasis to muscle, properties of the primary tumor may also be involved. It is important, furthermore, to differentiate between a primary soft tissue sarcoma and metastatic carcinoma to muscle because the treatment and prognosis are markedly different.

Although the presence of a soft tissue mass caused by metastatic carcinoma may easily be misdiagnosed as a soft tissue sarcoma on physical examination and imaging studies, (10) the current literature does not present any clinical or radiographic characteristics that help to distinguish between the two. (18) Whereas 50% of carcinomas and sarcomas metastatic to muscle occur in the lower extremity, a higher percentage of upper extremity carcinomatous metastases (26%) have been reported than soft tissue sarcomas (10%). In addition, most of the reported cases are located in one muscle group or in one part of the body. (27-29)

Although various imaging studies were used to identify metastases to muscle, none were specific for differentiating among carcinoma, sarcoma, and other muscle disorders. Plain radiographs, radionuclide scanning, and angiography have not been beneficial in differentiating carcinoma from sarcoma, (17) though MRI has been thought to be superior to CT (30,31); CT-guided fine needle aspiration provides a rapid, minimally invasive means of diagnosis. (18)

Treatment options include radiation therapy, surgery, chemotherapy, or a combination of the three. Reports suggest that surgical resection followed by adjuvant radiation or chemotherapy provides excellent palliative results. (32-34) Although a solitary metastasis less than 4 cm in diameter can be treated by excisional biopsy, (35) one report (18) suggests that a less invasive approach may be better because of the lower incidence of functional disability, as well as the poor survival rate of these patients. Surgical resection is often reserved for those lesions that cannot be controlled locally with radiation or when tumor growth results in neurologic deficit.

CONCLUSION

Although metastasis to skeletal muscle is extremely uncommon, physicians must be aware of its occurrence, since its detection often requires specific evaluation. Differentiation between a primary soft tissue sarcoma and metastatic carcinoma to muscle is important, since their treatment and prognosis are so markedly different. The current literature does not provide any clinical or radiographic characteristic (plain x-ray or bone scan) that distinguishes metastatic carcinoma to muscle from primary soft tissue sarcoma. (18) However, MRI appears promising. It should be considered earlier in the diagnostic workup. Treatment remains palliative, since metastatic carcinoma to muscle continues to be a late event with a poor overall prognosis.

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RELATED ARTICLE: KEY POINTS

* Metastasis to skeletal muscle is a rare event.

* Differentiation between a primary soft tissue sarcoma and metastatic carcinoma to muscle is important, since their treatment and prognosis are markedly different.

* The role of specific tests such as magnetic resonance imaging and computed tomography-guided biopsy for the early detection of metastasis to skeletal muscle is discussed.

* Treatment remains palliative, since metastatic carcinoma to muscle continues to be a late event with an overall poor prognosis.

From the Ralph H. Johnson Veterans Affairs Medical Center, Medical University of South Carolina, Charleston.

Reprint requests to Shakaib U. Rehman, MD, Medical University of South Carolina, Ralph H. Johnson Veterans Affairs Medical Center, 109 Bee Street, Charleston, SC 29401.