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Mediastinal Lesions Flashcards

1
Q

What are the two main differential diagnoses for an incidental encapsulated solid mass in the anterior mediastinum of an adult?

A

Lymphoma

Thymoma

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2
Q

What is the most common neoplasm of the anterior mediastinum?

A

Thymoma

Usually affects middle-aged and older adults and is often incidentally found (rarely extrinsic compression may cause symptoms)

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3
Q

Why are the terms “invasive” and “noninvasive” used instead of benign and malignant for thymomas?

A

Invasive thymomas may not show evidence of malignancy on pathology but can be difficult to treat and aggressive

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4
Q

What are the imaging features indicative of a thymoma being invasive?

A

Mediastinal fat invasion
Vascular invasion
Pulmonary invasion
Pleural invasion/mets

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5
Q

How can MR be useful in differentiating benign thymic conditions from noeplasms?

A

Using fat suppression or chemical shift sequences, MR can differentiate the fatty composition of thymic hyperplasia from the more soft tissue components of thymoma and lymphoma

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6
Q

How can MR be useful in confirming a thymic cyst?

A

Pre- and post-contrast images will show lack of enhancement

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7
Q

What is the most common condition associated with thymoma?

A

Patients with thymoma have a 30-40% likelihood of having myasthenia gravis

A smaller percentage (10-15%) of patients with myasthenia gravis will have thymoma

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8
Q

Other than myasthenia gravis, name four conditions associated with thymoma

A

Pure red cell aplasia
Hypogammaglobulinaemia
SLE
RA

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9
Q

What is the treatment of choice for thymoma?

A

Surgical excision, which in the setting of noninvasive thymoma can often be accomplished transcervically, avoiding the need for median sternotomy

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10
Q

Which type of lymphoma most commonly presents in the anterior mediastinum?

A

Hodgkin’s lymphoma

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11
Q

Other than Hodgkin’s lymphoma, which other form of lymphoma has a propensity for the anterior mediastinum in young adults and can present with symptoms related to compression of vessels and the airway?

A

Diffuse large B cell lymphoma

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12
Q

Which radiographic signs can be used to confirm an anterior mediastinal location of a mass on the frontal chest x-ray?

A

Hilum overlay sign

Preservation of the posterior mediastinal lines, descending thoracic aortic stripe and paravertebral lines

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13
Q

What type of biopsy is required for lymphoma?

A

Fine needle aspiration for flow cytometry and core biopsy

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14
Q

What is the most common germ cell tumour of the mediastinum and does it have a gender predilection?

A

Mature teratoma

No gender predilection

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15
Q

What densities can be seen in a mature teratoma?

A

Soft tissue
Fat
Calcification
Formed teeth and/or fat-fluid levels are diagnostic

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16
Q

Are teratomas benign or malignant?

A

Benign

If components of other germ cell tumour lines are present they are more appropriately referred to as mixed germ cell tumours

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17
Q

What imaging feature can help in distinguishing benign and malignant germ cell tumours?

A

The ratio of fluid/fat to soft tissue.

In benign lesions, the fat/fluid components are far greater than any soft tissue element

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18
Q

How are teratomas managed?

A

Because of the mass effect and very small chance of malignant elements, surgical excision is the treatment of choice

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19
Q

Mediastinal germ cell tumours account for approximately ___% of anterior mediastinal masses in adults

A

15%

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20
Q

After mature teratomas, which two broad classes of germ cell tumour occur in the mediastinum?

A

Seminomas

Non-seminomatous malignant germ cell tumour

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21
Q

What is the most common malignant germ cell tumour?

A

Seminoma

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22
Q

While teratomas are seen in relative equal frequency in both sexes, malignant germ cell tumours are seen more commonly in ____

A

Young male patients

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23
Q

What types of nonseminomatous malignant germ cell tumours exist and why are grouped together?

A

Embryonal cell carcinoma
Yolk sac tumour
Choriocarcinoma
Mixed cell types

Tend to be grouped together because of their rarity and poor prognosis. They tend to look similar on CT imaging

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24
Q

Which serologic tumour markers are tested and followed in nonseminomatous malignant germ cell tumours?

A

LDH
Alpha fetoprotein
Beta-HCG

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25
How are the different germ cell tumours treated?
Mature teratomas are surgically excised Seminomatous germ cell tumours are treated with radiation with or without surgical resection Nonseminomatous malignant germ cell tumours have the worst prognosis and are usually treated with chemotherapy and sometimes surgical resection
26
What are the differential diagnoses for a right cardiophrenic angle mass?
``` Foramen of Morgagni hernia Pericardial cyst Abundant pericardial fat Lymphadenopathy/lymphoma Other anterior mediastinal mass (thymoma, germ cell tumour) ```
27
What is a foramen of Morgagni hernia and how common are they?
Result from a defect in the attachment of diaphragmatic muscle fibres to the costal margin and central tendon of the diaphragm. Relatively rare (<3% of diaphragmatic hernias)
28
Which side are foramen of Morgagni hernias more commonly found and what do they usually contain?
Right sided Herniated omentum or portions of the transverse colon
29
What is the risk of malignancy for a retrosternal goitre?
Low but significant, ranging from 3-21%
30
How do goitres cause symptoms?
Direct mass effect - airway compromise, vascular compression
31
What is the difference between a primary and secondary retrosternal goitre?
Approximately 1% of goitres are considered primary retrosternal lesions with no communication with the cervical thyroid. Secondary retrosternal goitres that communicate with the cervical thyroid may display a cervicothoracic sign (extension of the mass above the thoracic inlet) in which the superior margin is ill defined due to blending with neck soft tissues, unlike the case of a posterior mediastinal mass, which is nicely outlined by the apical portions of the lung.
32
What is the aetiology of a thymic cyst?
Arise congenitally from embryonic remnants along the thymopharyngeal duct from the upper neck to the anterior mediastinum. May also occur in the setting of mediastinal radiation or chemotherapy.
33
What is the typical density of a thymic cyst?
Typically fluid attenuation but occasionally will be higher in attenuation due to haemorrhage or proteinaceous debris. If soft tissue nodularity is present, cystic neoplasms must be considered, such as teratoma, cystic thymoma or necrotic lymphoma
34
Multiple cysts in the thymus can be a manifestation of which two conditions?
Lymphoepithelial cysts in HIV/AIDS | Langerhans cell histiocytosis (especially in children)
35
How are thymic cysts managed?
No intervention | Most commonly incidentally detected
36
On chest x-ray, the normal right paratracheal stripe should be less than ___mm
<4mm When larger, a mediastinal mass (usually lymphadenopathy) should be suspected
37
What is the normal contour of the aortopulmonary window?
Concave When convex, a mediastinal mass (usually lymphadenopathy) should be suspected
38
How can enlarged pulmonary arteries be distinguished from hilar lymphadenopathy?
Difficult distinction but the visualisation of an inferior border is a useful finding in lymphadenopathy; it is not usually seen with enlarged vessels
39
What is Garland's triad?
Bilateral hilar and right paratracheal lymphadenopathy in sarcoidosis
40
What is the differential diagnosis for a middle mediastinal mass?
Foregut duplication cyst Oesophageal mass Lymphadenopathy Vascular lesion
41
What are foregut duplication cysts?
Generic term covering both bronchogenic cyst and oesophageal duplication cyst (difficult to differentiate the two on imaging) A bronchogenic cyst will contain respiratory epithelium and cartilage. An oesophageal duplication cyst will be lined with smooth muscle and will not contain cartilage. An infected or haemorrhagic cyst will result in denuded and featureless epithelium - 50% or more of oesophageal duplication cysts will have attenuation greater than water from protein or blood products
42
What further imaging is required when encountering a foregut duplication cyst?
If CT demonstrates a well-circumscribed mass that has a thin wall and measures fluid attenuation (<15 HU), no further imaging evaluation is required. MR is useful in complex duplication cysts because uniform high signal will be seen on the T2 sequence. The T1 signal will be variable due to the content of protein and blood products.
43
Where are foregut duplication cysts normally found?
Most bronchogenic cysts are found in the subcarinal or right paratracheal regions. Oesophageal duplication cysts can occur anywhere along the course of the oesophagus.
44
What is the management of duplication cysts?
As duplication cysts can increase in size from infection or haemorrhage, they are often resected. Some surgeons have also advocated aspiration for treatment and diagnosis; however, the cysts may recur following aspiration.
45
What is the most likely differential for a posterior mediastinal mass in an adult? What are the other differential diagnoses?
Nerve sheath tumour is most likely (neurofibroma, schwannoma or neurolemmoma). In children and young adults, they may be of sympathetic ganglia origin (ganglioneuroma, neuroblastoma or ganglioneuroblastoma). Other differentials include lympphadenopathy, extramedullary haematopoiesis, lateral meningocele and vertebral osteomyelitis/discitis
46
What is the cervicothoracic sign?
Superior extension of a mass above the clavicles. Because the anterior lung stops at the level of the clavicles, a mass demonstrating this sign must be posterior in the thorax or arising from the neck.
47
What is the imaging appearance of a nerve sheath tumour?
Posterior mediastinal mass. Nerve sheath tumours tend to be one or two rib interspaces in the z-axis, while sympathetic ganglia tumours are longer. Schwannomas and neurofibromas are well circumscribed and round. Because of myelin and occasionaly cystic regions, they tend to be lower than muscle in density. On MR, they tend to be higher than muscle on T2 and often enhance with a targetoid appearance. Neural foraminal enlargement may not be seen with nerve sheath tumours, but osseous remodelling is common.
48
How do nerve sheath tumours most commonly present?
Scwannomas are usually incidental, but one third of patients with neurofibromas will have neurofibromatosis.
49
What is the management of a nerve sheath tumour?
They may be resected because of local symptoms. The risk of malignant transformation is low in isolated schwannomas.
50
Which organism is most commonly responsible for discitis?
Staphylococcus aureus, usually haematogeneously spread from another site Discitis from atypical organisms (including mycobacterial infection) may involve more than one level
51
What are the CT features of discitis?
Endplate destruction and adjacent soft tissue phlegmon or stranding
52
What are the MR features of discitis?
Increased T2 signal in the disc and adjacent vertebra with enhancement
53
How is discitis confirmed and treated?
Biopsy and culture, usually under image guidance. This will guide antibiotic therapy. In more advanced cases, surgical debridement and stabilisation may be required.
54
When does extramedullary haematopoeisis occur?
EMH is due to red blood cell destruction or lack of production and can be seen in spherocytosis, thalassaemia or other congenital anaemias. It is rarely seen with sickle cell disease, myelofibrosis or leukaemias/lymphomas.
55
Is paravertebral EMH usually unilateral or bilateral?
Usually bilateral paravertebral masses that do not connect. The lack of a connection or isthmus suggests that the masses arose independently and that a lesion did not simply grow to the other side.
56
How can the diagnosis of EMH be confirmed?
Tc-99m sulfur colloid study, which will demonstrate uptake in bone marrow-producing elements
57
What bony changes can be seen in vertebrae and ribs with EMH?
Marrow expansion which may result in coarsened bone trabeculation
58
Apart from bone and the paravertebral regions, where else can extramedullary haematopoiesis be seen?
Almost anywhere, including the liver, spleen, peritoneum, pleura and bladder
59
What happens when the anaemia resolves?
The areas of EMH may take on fat attenuation
60
What treatment is required for EMH?
Once the diagnosis is established, no treatment is required other than for supportive care for the patient's anaemia. In the rare circumstance that the EMH is resulting in local mass effect, decompressive treatment would be needed.
61
What are some potential causes of acute mediastinitis?
``` Oesophageal perforation Cardiac surgery Extension of pneumonia Retropharyngeal infection Sternoclavicular septic arthritis ```
62
What are the CT features of mediastinitis?
Enlargement and mediastinal fat stranding | Pneumomediastinum occasionally seen.
63
When should fluid and gas collections begin to resolve in the non-infected postoperative mediastinum?
Should begin to resolve by 3 weeks
64
What is fibrosing mediastinitis?
Idiopathic dense fibrous tissue within the mediastinum. In the US, most cases are associated with histoplasmosis infection. The histoplasmosis antigen incites an autoimmune fibrotic reaction. Other associations include infection (fungal or mycobacterial), autoimmune diseases and medications.
65
How does fibrosing mediastinitis present?
Patients present with compressive symptoms on the superior vena cava, pulmonary veins and/or pulmonary arteries. The bronchi are usually affected after the veins and arteries. Haemoptysis can be a presenting symptom due to the bronchial collaterals. Rarely, FM can compress the coronary arteries resulting in coronary ischaemia, or the oesophagus resulting in dysphagia
66
Is fibrosing mediastinitis a unilateral or bilateral process?
Tends to be unilateral (usually on the right side) and may result in unilateral absence of perfusion.
67
Is calcification on CT required to make the diagnosis?
No, but it is often present. In the more diffuse form of FM (which is not as clearly associated with prior infection), calcification is less common.
68
What is the role of biopsy in fibrosing mediastinitis?
When the imaging appearance is characteristic, no biopsy may be performed. Biopsy may be performed to exclude neoplasm. Rarely are organisms retrieved.
69
What is the goal of management of fibrosing mediastinitis and how is this achieved?
Management is directed at relieving the vascular compromise. This includes stenting and angioplasty.
70
What is the differential diagnosis for low-attenuating lymphadenopathy?
Granulomatous disease (histoplasmosis and tuberculosis) Lymphoma Metastases
71
A lymph node which demonstrates a thin rind of peripheral enhancement with a low-attenuating necrotic centre is suggestive of ______
Active granulomatous inflammation (either histoplasmosis or tuberculosis)
72
Can mycobacterial or fungal nodal involvement occur without pulmonary involvement?
Yes, this is especially true in children
73
In HIV-positive patients, which specific organism can present with low-attenuating, rim enhancing lymphadenopathy?
Mycobacterium avium intracellulare
74
What percentage of lymphoma will present with low attenuating lymphadenopathy?
25%
75
Which metastases present with low attenuating lymphadenopathy?
Lung Seminoma Gastric Ovarian
76
Other than TB, histoplasmosis, lymphoma and metastases, what other rare condition will present with low-attenuating lymph nodes (closer to fat in attenuation)?
Whipple's disease - rare infectious arthropathy caused by the actinobacteria Tropheryma whipplei. Presents with with small bowel findings and fat-containing nodes from an abundance of macrophages.
77
What is an unusual mimic for low attenuating lymph nodes (hint: occurs in a phakomatosis)?
Plexiform neurofibromas in the setting of neurofibromatosis. These nerve sheath tumours are myelin-rich and are therefore low in attenuation on CT.
78
Initial management step when low-attenuating lymph nodes are identified on CT?
The possibility of acute tuberculosis requires the patient to be placed in isolation until proven not contagious. Sputum should be collected for M/C/S. Patients may undergo bronchoscopy and biopsy for culture if the diagnosis cannot be made less invasively.
79
What are the differentials for hypervascular lymphadenopathy?
Castleman disease | Hypervascular metastases - especially RCC, melanoma and thyroid cancers
80
What is angiofollicular lymph node hyperplasia also known as?
Castleman disease | Also known as giant lymph node hyperplasia
81
What is Castleman disease?
Uncommon benign B-cell lymphoproliferative condition with two distinct subtypes - hyaline vascular and plasma cell.
82
How does hyaline vascular Castleman disease most commonly present?
Unicentric disease with a dominant, often mediastinal, nodal mass or conglomerate without systemic symptoms
83
How does plasma cell Castleman disease most commonly present?
Multicentric disease involving multiple nodal stations in the neck, chest and/or abdomen, along with systemic symptoms of fever, weight loss and anaemia
84
Which type of Castleman disease is more common?
Hyaline vascular
85
Which patients have a higher incidence of Castleman disease (in particular plasma cell type)?
Patients with Kaposi sarcoma and HIV
86
If hyperenhancing lymphadenopathy is encountered, what is the next step?
Evaluation for a hypervascular primary malignancy is necessary, possibly requiring whole body CT or PET-CT
87
If Castleman disease is considered in the differential diagnosis, what should be the next step?
Surgical excision is usually necessary as the architectural details of the node required for diagnosis cannot be obtained with FNA.
88
How are the two types of Castleman disease treated?
Unicentric hyaline vascular CD is usually cured by surgical excision. Multicentric plasma cell CD is treated with a combination of chemotherapy, immunosuppression/steroids and/or radiation

Chest Radiology (1 decks)

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