In order to better understand the etiology of distant metastasis
with no regional lymph node swelling, a review of 891 patients with
lung cancer who were admitted to our hospital from 1983 to 2000 has
been undertaken. TNM staging1was performed by chest CT,
abdominal CT, head CT, or brain MRI scans, and bone scintigraphy.
Clinical stage N0 was defined when neither mediastinal nor hilar lymph
node measured > 1.0 cm in diameter as detected on enhanced chest CT
scan.2 Thirty-one patients (3.5%) had distant metastasis
with no regional lymph node swelling at the time of diagnosis.
Histology included 26 adenocarcinomas (83.9%), 2 squamous cell
carcinomas, 2 large cell carcinomas, and 1 small cell carcinoma.
Twenty-three patients had good performance status (performance status
of 0 to 1). The size of the primary lesion was not necessarily large
(30 mm; nine patients). In 21 patients, metastases were confined in
only one organ. The most common organs were lung, bone, and brain.
Silent metastasis detected only by the imaging procedures was found in
21 patients. All these metastases detected by imaging procedures were
confirmed as true-positive by following their clinical courses.