Lung Cancer.pdf

12 J.B. Putnam, Jr., F.V. Fossella, and R. Komaki
may also provide clues to the tumor’s histologic subtype: squamous carcinomas
tend to be large and centrally located, adenocarcinomas tend to
be more peripherally located, and SCLCs tend to be large, located centrally
or near the hilum, and associated with bulky mediastinal lymphadenopathy.
On chest radiography, the relationship of the mass to the thoracic structures
and mediastinum and whether the mass appears limited or diffuse
should be noted. In addition, attention should be paid to whether the following
features are present: cavitation, segmental or lobar collapse or consolidation,
hilar or mediastinal enlargement, evidence of intrathoracic
metastasis, and evidence of extrapulmonary intrathoracic extension.
CT of the chest and upper abdomen provides more detail than chest radiography
about the surface characteristics of the tumor, the location of
the tumor in relation to the mediastinum and mediastinal structures, and
metastasis to lung, bones, liver, and adrenals. CT will also reveal any enlargement
of the mediastinal lymph nodes. Although CT cannot accurately
or consistently predict invasion, it can reveal the size and the density
of mediastinal nodes. CT of the chest and upper abdomen has a
specificity of 65% and a sensitivity of 79% in the identification of mediastinal
lymphadenopathy. When lymph nodes are larger than 1.5 cm in diameter,
CT has a specificity of approximately 85% in the identification of
metastasis to mediastinal lymph nodes.
Evaluation of Enlarged Mediastinal Lymph Nodes
If chest radiography or CT of the chest and upper abdomen indicates that
mediastinal lymph nodes are enlarged ( 1 cm), biopsy is required to determine
whether the nodes are involved with lung cancer metastases and
to define the extent of such involvement. The probability of metastatic involvement
in lymph nodes measuring 1 cm or larger is 30%. Other causes
of mediastinal lymphadenopathy include mediastinal inflammation, peripheral
pulmonary obstruction, atelectasis, consolidation, bronchitis, pneumonitis,
and pneumonia; in addition, some patients may have normally
enlarged mediastinal lymph nodes.
Methods available for mediastinal lymph node biopsy include transbronchial
biopsy (for technical details, see the section Bronchoscopy later
in this chapter), cervical mediastinoscopy, extended cervical mediastinoscopy,
anterior mediastinotomy (Chamberlain procedure), videoassisted
thoracoscopy, and fine-needle aspiration. The procedure of choice
depends on the location of the enlarged nodes and the patient’s performance
status. Positron emission tomography (PET) is also being investigated
as an alternative technique or more likely a technique complementary
to mediastinoscopy for identifying potential metastatic involvement
of mediastinal nodes. Pathologic review of the biopsy specimen is required
before initiation of treatment.