Pediatrics: Mediastinal Masses Flashcards
What characteristics of a thymus should raise suspicion for cancer?
- Abnormal size (e.g. large thymus in a 15 y/o)
- Heterogeneous appearance
- Calcification
- Compression of airway or vascular structure
What causes thymus rebound?
An acute stressor (pneumonia, radiation, chemotherapy, burns, corticosteroid therapy etc.)
Note: The stressor actually causes the thymus to shrink, but after it will rebound to normal or above normal size (and can be FDG avid on PET).
What is the most common abnormal mediastinal mass in children?
Lymphoma
Note: The thymus if the most common thing identified as a mediastinal mass, but is normal.
Anterior mediastinal mass with calcifications in a child (no prior treatment)…
Think teratoma
Note: Lymphomas can calcify following treatment.
Starting at what age should an anterior mediastinal mass make you concerned about lymphoma?
10 years
Note: After age 10, the thymus should be fairly small. Look for cervical lymphadenopathy.
Pt has an extra gonadal germ cell tumor…
Think Klinefelter’s syndrome (47 XXY)
What are the major germ cell tumors that can arise in the anterior mediastinum?
- Teratoma
- Seminoma
- Non-seminomatous germ cell tumors
Large anterior mediastinal cystic mass with macroscopic fat and calcification…
Teratoma (germ cell tumor)
Large anterior mediastinal solid mass that “straddles the midline” and appears lobulated…
Think seminoma (germ cell tumor)
Note: Lymphoma could also look like this.
Large anterior mediastinal mass with regions of hemorrhage and necrosis +/- invasion of the pulmonary parenchyma…
Think non-seminomatous germ cell tumor
Middle mediastinal lymphadenopathy…
Think granulomatous disease (fungal infection/tuberculosis) or lymphoma
Adolescent with hilar adenopathy, splenomegaly, and fatigue…
Think mononucleosis (EBV/CMV infection)
What are the major categories of duplication cysts you may find in the mediastinum?
- Bronchogenic
- Enteric
- Neuroenteric (posterior mediastinal)
Middle mediastinal cyst adjacent to the airway…
Think bronchogenic duplication cyst
Mediastinal cyst that abuts the esophagus…
Think enteric duplication cyst
You see an air-fluid level in what you assume is a mediastinal enteric duplication cyst…
Normal finding (communication with the esophageal lumen is common)
What is the most common posterior mediastinal mass in a child under 2 y/o…
Neuroblastoma
Posterior mediastinal mass in a child under the age of 10…
Think malignancy (most likely neuroblastoma)
Note: Posterior mediastinal masses in children over age 10 are more often benign.
Posterior mediastinal mass in a child over age 10…
Think benign lesions:
- Ganglioneuroma/neurofibroma (round masses)
- Neuroentric cyst (if cystic)
- Extramedullary hematopoiesis (if there is coarse bone trabeculation or history of anemia)
What is the difference between a ganglioneuroma, ganglioneuroblastoma, and a neuroblastoma?
Cellular differentiation and aggression:
- Neuroblastoma (undifferentiated, aggressive)
- Ganglioneuroblastoma (intermediate differentiation/aggression)
- Ganglioneuroma (most differentiated/least aggressive)
Note: The aggressive neuroblatomas mostly occur in kids under the age of 10.
Askin tumor
A primitive neuroectodermal tumor of the chest wall (considered as part of the Ewing sarcoma spectrum)
Imaging appearance of an Askin tumor
Large, heterogeneous mass with enhancing solid components arising from the chest wall that tends to displace adjacent structures (rather than invade them) early on (though invasion does occur if they get large)
Posterior mediastinal cyst in a pt with scoliosis…
Think neuroenteric cyst
Note: These are usually associated with a vertebral anomaly (scoliosis, hemivertebrae, split cord, etc.).
Bilateral, smooth, sharply-demarcated soft tissue densities around the spine in the lower mediastinum…
Think extra medullary hematopoiesis
Note: Look for hepatosplenomegaly.
Common causes of extra medullary hematopoiesis
- Myeloproliferative disorders
- Bone marrow infiltration (e.g. sickle cell disease)
What type of lymphoma is most common in children?
Hodgkins (4x more common than non-Hodgkins)
Hodgkins lymphoma involves the _____ in 90% of cases
Thymus
Best way to differentiate a normal thymus from lymphoma
Age:
Under 10 y/o = thymus
Over 10 y/o = lymphoma
Water density cystic structure in the anterior mediastinum…
Think lymphangioma
Rounded posterior mediastinal mass in a pt over age 10…
Think ganglioneuroma or neurofibroma
Huge mass in the chest (e.g. taking up an entire hemithorax or nearly the entire thorax)…
Think Askin tumor, AKA primitive neuroectodermal tumor of the chest wall, AKA Ewings spectrum (usually older than 10 y/o; look for rib erosions)
Think pleuropulmonary blastoma (if pt is less than 2 y/o)
