the radiological.html
The radiological appearance of metastatic
cystic lesions
P Barnardt, MB ChB, Dip Oncol
J du Toit, MB ChB
Department of Medical Imaging and Clinical Oncology, Tygerberg Hospital, Parow
Corresponding author: P Barnardt (pieterb@sun.ac.za)
Abstract
Introduction.
Cystic and cavitatory pulmonary lesions are abnormalities encountered
on chest computed tomography (CT). Malignant lesions, including
metastases, rarely present as cystic lesions; we report on two such
cases: a man with advanced carcinoma of the left testis, and a woman
with epithelioid trophoblastic tumour.
Discussion.
The lungs are the most common site for metastases from non-pulmonary
neoplasms. The appearance of cystic lesions in the lung in malignancy
is rare and predisposes to spontaneous pneumothoraces. Multiple cystic
lesions occur commonly in bronchus carcinoma and also sarcoma, bladder
cancer and, less commonly, lymphoma and metastasis. Both chemotherapy
and immune suppression can induce cavitation in malignant lesions.
Tumour necrosis and tumour infiltration of air-containing spaces with a
check-valve mechanism are postulated for causing these cystic lesions.
Spontaneous resolution is the rule. Close follow-up is recommended as
these spaces may become infected.
Conclusion.
CT is the mainstay of diagnostic imaging in cancer patients. Cystic
lung lesions are caused by a diverse array of pathological processes,
and are rare in metastatic disease.
Introduction
Cystic and cavitatory pulmonary lesions are
abnormalities frequently encountered on chest radiography and computed
tomography (CT). A cyst is defined as any round circumscribed space
that is surrounded by an epithelioid or fibrous wall of variable
thickness. The underlying nature of these lesions may be apparent, as
in the case of bullae associated with emphysema, but may pose a
diagnostic challenge. Generally, malignant lesions including metastases
rarely present as cystic lesions.1
High-resolution CT of the chest helps to define morphological features
that may serve as clues regarding the nature of cystic and cavitatory
lung lesions. A well-established differential list for consideration
exists for these radiological phenomena (Table I).1
,
2
We report two cases of metastatic malignant tumors with cystic
pulmonary lesions post-chemotherapy on radiological imaging: a man with
advanced non-seminomatous germ cell tumour (NSGCT) and a woman with
epithelioid trophoblastic tumour (ETT).
Prior written informed consent and local ethics committee approval was obtained.
Case 1
A 22-year-old man presented at the
Tygerberg
Hospital Oncology Unit post-orchidectomy for a large left testicular
mass. Clinical examination revealed a palpable para-umbilical mass of
10 x 15 cm. The post-operative blood examinations showed raised
hormonal markers of alpha fetoprotein (AFP) of 15 167 µg/l (0.0 - 9.0 µg/l), β-human
chorionic gonadotropin (HCG) 6104 IU/l (<5 IU/l) and a lactate
dehydrogenase (LDH) value of 313 U/l (100 - 190 U/l). Staging
examinations included a chest X-ray (CXR), which showed multiple
bilateral lung nodules, and thoracic and abdomino-pelvic CT that
confirmed multiple diffuse nodules in both right and left lungs in
keeping with metastases (Fig. 1a). Significant left para-aortic and
porta-hepatic lymphadenopathy was also demonstrated. These features
were suggestive of metastatic testicular cancer. A brain CT was normal,
with no evidence of metastatic disease.
Microscopic examination revealed tumour cells
displaying a trabecular pattern with papillary and pseudoglandular
structures, as well as solid areas. Extensive necrosis and haemorrhage
were also seen. These changes were consistent with embryonal carcinoma
and yolk sac elements, and the histological features confirmed a
non-seminomatous germ cell tumour (NSGCT) of the left testis. The
patient was staged according to the European Germ Cell Cancer Consensus
Group as a pT2 N3 M1a S2 (Stage IIIa), intermediate risk NSGCT. He was
offered systemic chemotherapy with the standard BEP regime (bleomycin
30 IU IV day 1, 8, 15; cisplatinum 20 mg/m2 IV day 1 - 5 and etoposide 100 mg/m2
IV day 1 - 5 every 21 days) and completed 6 cycles. His hormonal
markers decreased with each consecutive cycle and normalised after
cycle 4.
Restaging CXR, chest CT and abdomino-pelvic CT were
compared with baseline investigations. In both lungs, the majority of
the previously demonstrated pulmonary lesions showed cystic
degeneration and a reduction in size (Fig. 1b). Individual small solid
lesions were still noted peripherally. The para-aortic lymph nodes were
still present but appeared smaller, demonstrating a partial response to
therapy. Owing to marker normalisation, the patient was referred to a
urology-oncology surgeon for a retroperitoneal lymph node dissection.
Case 2
A 35-year-old woman presented with a history of secondary infertility, persistent vaginal bleeding, raised β-HCG
and an ultrasonic appearance of a molar pregnancy. Her staging
examinations include a CXR revealing numerous small bilateral lung
lesions and an abdominal CT that confirmed a single liver metastasis. A
brain CT was normal, with no signs of metastatic disease.
Microscopic
sections of the tumour showed haemorrhage, necrosis and numerous
fragments of malignant trophoblastic tissue of intermediate origin. The
cells were epithelioid in shape with hyperchromatic nuclei.
Syncytotrophoblastic giant cells were few. In view of the morphology
and the intense positivity of p63 and K167 immunohistochemistry, the
features were in keeping with an epithelioid trophoblastic tumour
(ETT). According to the revised International Federation of Gynecology
and Obstetrics (FIGO) classification for gestational neoplastic disease
(GND), she had Stage IV disease. Chemotherapy consisted of etoposide
100 mg/m2 IV day 1 - 5 and cisplatinum 20 mg/m2 IV day 1 - 5 every 21 days. She completed 6 cycles with a slow decline in β-HCG.
Restaging examinations included a chest and
abdominal CT. Numerous cystic metastatic lesions were detected
bilaterally throughout both lung fields secondary to systemic
treatment. Bilateral pneumothoraces were present (Fig. 2). A single
hypodensity was detected in the periphery of the right lobe of the
liver but was, however, too small to characterise and could represent
either a benign cyst or a cystic metastasis. The remainder of the
abdomen was clear. Currently, the patient continues with second-line
multi-agent chemotherapy on a weekly basis.
Discussion
The appearance
of cystic lesions in the lung in malignancy is rare and best described
radiologically by chest CT. Cysts appear radiologically as rounded
parenchymal lucencies or as low-attenuating areas with a well-defined
interface of normal lung, and are usually thin-walled (<2 mm). Cysts
in the lung usually contain air but can also contain fluid or solid
material.1
,
3 Important parameters in evaluating cystic and cavitatory lesions are (i) the tempo of disease (acute versus chronic) and (ii)
the clinical context. A chronic process is more likely, owing to
neoplastic disease, long-standing inflammatory or fibrotic disorders,
and congenital lesions. The presence of cysts and cavities in the lung
predisposes to the occurrence of spontaneous pneumothoraces.1
,
5
The lungs are the most common site for metastases
from non-pulmonary neoplasms. These are typically round and
well-defined; however, they may present radiologically with a spectrum
of unusual appearances including cavitation, calcification or
surrounding ill-defined haemorrhage. Numerous cystic and cavitatory
lesions occur frequently in bronchus carcinoma (10% - 15%) and are
usually associated more with squamous cell carcinoma than other cell
types. However, they also occur with sarcoma, transitional cell
carcinoma of the bladder and, less commonly, with lymphoma and
metastasis.4
,
5 The frequency of cavitation in pulmonary metastases is approximately 4%, as opposed to 9% in primary bronchogenic carcinoma.5
Both
chemotherapy and immune suppression are known to induce cavitation in
malignant lesions. Several mechanisms are postulated: tumour necrosis
secondary to rapid tumour kill in chemosensitive tumors, and tumour
infiltration of air-containing structures with a check-valve mechanism
are some.5
There is a suggestion that ETT may not be as chemosensitive as other
gestational trophoblastic diseases, but testis cancer is a highly
chemosensitive tumour. Both our patients presented post-chemotherapy
with cystic pulmonary lesions and, in the case of the ETT patient,
bilateral pneumothoraces appeared as a result of ruptured cavitations. Spontaneous
resolution is the rule. Close follow-up in immune-suppressed patients
is recommended as these spaces may become infected.1
Conclusion
CT is the mainstay of diagnostic imaging in cancer
patients as it is non-invasive, highly sensitive, and specific for a
range of diseases. Cystic and cavitatory lung lesions are caused by a
diverse array of pathological processes and are rare in metastatic
disease. We have described two cases of cystic pulmonary metastases
post-chemotherapy, with the aim of highlighting to both clinicians and
radiologists the atypical appearances of malignant disease and the
associated diagnostic possibilities.
1. Ryu HJ, Swensen SJ. Cystic and cavitary lung diseases: Focal and diffuse. Mayo Clin Proc 2003;744-752.
1. Ryu HJ, Swensen SJ. Cystic and cavitary lung diseases: Focal and diffuse. Mayo Clin Proc 2003;744-752.
2. Cantin L, Bankier AA, Eisenberg RL. Multiple cystic-like lung lesions in the adult. AJR 2010;194(1):1-11.
2. Cantin L, Bankier AA, Eisenberg RL. Multiple cystic-like lung lesions in the adult. AJR 2010;194(1):1-11.
3. Hansell DM, Bankier AA, MacMahon H, et al. Glossary of terms for thoracic imaging. Radiology 2008;246(3):697-722.
3. Hansell DM, Bankier AA, MacMahon H, et al. Glossary of terms for thoracic imaging. Radiology 2008;246(3):697-722.
4. Godwin JD, Webb WR, Savoca CJ, et al. Multiple, thin-walled cystic lesions of the lung. AJR 1980;135:593-604.
4. Godwin JD, Webb WR, Savoca CJ, et al. Multiple, thin-walled cystic lesions of the lung. AJR 1980;135:593-604.
5. Topal NB, Oruc E, Gokalp G, Topal U. Atypical pulmonary metastases: Radiologic appearances. Indian J Radiol Imaging 2007;17:181-185.
5. Topal NB, Oruc E, Gokalp G, Topal U. Atypical pulmonary metastases: Radiologic appearances. Indian J Radiol Imaging 2007;17:181-185.
Table I. Differential considerations for multiple
cystic lung lesions
Pulmonary Langerhans cell histiocytosis
Pulmonary lymphangioleiomyomatosis
Lymphocytic interstitial pneumonia
Pneumatoceles
Neurofibromatosis type 1
Tracheobronchial papillomatosis
Metastases (rare)
Fig. 1. Chest computed tomography of metastatic
testicular cancer. (A) Pre-treatment: Note bilateral lung nodules and
masses. (B) Post-treatment: Note thin-walled cystic lesions.
Fig. 2. Chest X-ray of metastatic liver cancer. (A)
Pre-treatment: Note numerous bilateral solid nodules, and (B)
Post-treatment: Note numerous bilateral pulmonary nodules that have
decreased in size and density with associated cystic degeneration owing
to chemotherapy.
Fig.
3. Lung CT of a patient with metastatic epithelioid trophoblastic
tumour (ETT). Note the irregular thin-walled cystic structures with
ruptured subpleural lesions, resulting in bilateral pneumothoraces.