Lung Mass Biography
(Source google.com)
In radiology, a solitary
pulmonary nodule (SPN) or coin lesion is a mass in the lungsmaller than 3
centimeters in diameter. It can be an incidental finding found in up to 0.2% of
chest X-rays and around 1% of CT scans. The nodule most commonly
represents a benign tumor such as a granuloma orhamartoma, but in around 20% of
cases it represents a malignant cancer, especially inolder adults and smokers.
Conversely, 10 to 20% of patients with lung cancer are diagnosed in this way.
Thus, the possibility of cancer needs to be excluded through further
radiological studies and interventions, possibly including surgical resection.
Theprognosis depends on the underlying condition. A solitary pulmonary nodulus
needs to be separated from larger lung tumors, smaller infiltrates or masses
with other accompanying characteristics. An often used formal radiological
definition is the following: a single lesion in the lung completely surrounded
by lung parenchyma (functional tissue) with a diameter less than 3 cm and
without associatedpneumonia, atelectasis (lung collapse) or lymphadenopathies
(swollen lymph nodes). ot every round spot on a radiological image is a coin
lesion: it should not be confused with the projection of a structure of the
chest wall or skin, such as a nipple, a healing rib fracture or
electrocardiographic monitoring.
The most important cause to
exclude is a form of lung cancer, including rare forms such as primary
pulmonary lymphoma, carcinoid tumor and a solitary metastasis to the lung
(common unrecognised primary tumor sites are melanomas, sarcomas or testicular
cancer). Benign tumors in the lung include hamartomas and chondromas. The most common benign coin
lesion is a granuloma (inflammatory nodule), for example due to tuberculosis or
a fungal infection. Other infectious causes include a pulmonary abscess,
pneumonia (including Pneumocystis carinii pneumonia) or rarely nocardial
infection or worm infection (such as dirofilariasis or dog heartworm
infestation). Lung nodules can also occur in immune disorders, such
asrheumatoid arthritis or Wegener's granulomatosis, or organizing pneumonia.
An SPN can be found to be an
arteriovenous malformation, a hematoma or an infarction zone. It may also be
caused by bronchial atresia, sequestration, an inhaled foreign body or pleural
plaque. Several features help to distinguish benign conditions from possible
lung cancer. The first parameter is the size of the lesion: the smaller, the
less risk for malignant cancer. Benign causes tend to have a well defined
border, whereas lobulated lesions or those with an irregular margin extending
into the neighbouring tissue tend to be malignant. If there is a central cavity, then a thin
wall points to a benign cause whereas a thick wall is associated with
malignancy (especially 4mm or less versus 16mm or more). In lung cancer,
cavitation can represent central tumor necrosis (tissue death) or secondary
abscessformation. If the walls of an airway are visible (air onchogram),
bronchioloalveolar carcinomais a possibility. An SPN often contains
calcifications. Certain patterns of calcification are reassuring, such as the
popcorn-like appearance of hamartoma. An SPN with a density below 15 Hounsfield
units on computed tomography tends to be benign, whereas malignant tumors often
measure more than 20 Hounsfield units. Fatty tissue inside hamartomas will have
a strongly negative value on the Hounsfield scale. The growth velocity of a lesion
is also informative: very fast or very slow growing tumors are rarely
malignant, in contrary to inflammatory or congenital conditions. It is
therefore important to retrieve previous imaging studies to see if a lesion was
presented and how fast its volume is increasing. This is more difficult for
nodules smaller than 1 centimeter. Moreover, the predictive value of stable
lesion over a period of 2 years has been found to be rather low and unreliable. The work-up in patients with a
solitary pulmonary nodule is based on an initial risk assessment. If the risk
of malignancy is thought to be low, follow-up imaging (usually serial CT scans)
can be planned at a later time. The frequency of further scans can be
determined by the patient's risk for cancer and the size of the nodule. If the
initial impression is that there is a high likelihood of cancer, then a surgical
intervention is appropriate (provided that the patient is fit for surgery). If there is an intermediate risk
of malignancy, further imaging with positron emission tomography (PET scan) is
appropriate (if available). Around 95% of patients with a malignant nodule will
have an abnormal PET scan, while around 78% of patients with a benign nodule
will look normal on PET (this is the test sensitivity and specificity). Thus,
an abnormal PET scan will reliably pick up cancer, but several other types of
nodules (inflammatory or infectious, for example) will also show up on a PET
scan. If the nodule has a diameter below 1 centimeter, PET scans are often
avoided because there is an increased risk of falsely normal results. Cancerous
lesions usually have a high metabolism on PET, as demonstrated by their high
uptake of FDG (a radioactive sugar). If the lesion is found on further imaging
to be suspicious, it should be surgically excised (via thoracotomy or
video-assisted thoracic surgery) to confirm the diagnosis by microscopical
examination.
No comments:
Post a Comment