Cortically Based Brain Neoplasms

• Astrocytoma May extend to cortex. Minimal or no enhancement or edema in low-grade astrocytomas. Calcification is uncommon.
• Oligodendrolioma: Slowly growing, well-differentiated neoplasms. Diffusely infiltrating, but appear well-circumscribed. Calcifications are seen in 80% of cases.
• Ganglioglioma: Well-circumscribed cystic lesion with nodule and minimal edema. Most commonly seen in the temporal and parietal lobes.
• Desmoplastic infantile glioma (DIG): Variant of ganglioglioma that is usually seen in the first 2 years of life. Low-grade tumor with good prognosis. More commonly seen in the frontal and parietal lobes. Cystic mass with with a cortically based nodule. Nodule is iso- to high-attenuation, T2-hypointense, and enhances. Some may also have a calcified rim.
• Dysembryoplastic Neuroepithelial Tumor (DNET): Look for "bubbly" appearance on MRI.
• Pleomorphic Xanthoastrocytoma: Look for a cortically based nodule in a cystic lesion.

See related post on cystic brain masses.

References

Koeller KK, Henry JM. From the archives of the AFIP: superficial gliomas: radiologic-pathologic correlation. Armed Forces Institute of Pathology. Radiographics. 2001 Nov-Dec;21(6):1533-56

Congenital Lobar Emphysema

Congenital lobar emphysema refers to progressive hyperinflaction of a lobe due to a check-valve mechanism at the bronchial level. There is no destruction of alveolar walls and the majority of cases are idiopathic. Malacia or stenosis of the bronchial cartilage can be seen in patients and are thought to represent possible etiologies. Cardiovascular anomalies can be seen in about 15% of cases.

The most commonly affected lobe is the left upper lobe (40%), followed by the right middle (35%) and upper (20%) lobes. The lower lobes are less commonly affected.

Most patients present before 6 months of age, most commonly with respiratory distress. Three clinical types can be defined based on the age of presentation: infancy (type I, most common), older children (type II, rare), or incidental in asymptomatic patients (type III, rare).

Chest radiographs obtained during the neonatal period may reveal the affected lobe to be opaque (because of retained fetal lung fluid) or diffusely reticular (due to distended lymphatic channels filled with fetal lung fluid). As the fluid clears by absorption, the affected lung progresses from alveolar opacification to interstitial reticulation to hyperlucency.

Mass effect from the expanded lobe or segment can compress adjacent lobes and structures, sometimes causing ipsilateral or contralateral atelectasis. The adjacent lobe collapses either caudad or cephalad but not medially. The ipsilateral rib spaces may be widened, the ipsilateral hemidiaphragm may be depressed, and there may be contralateral mediastinal shift.

Differential considerations for the hyperlucent lung include pneumothorax, lung cysts (simple or acquired), foreign body with air trapping, and pulmonary sling (only vascular ring associated with asymmetric lung aeration).

The images above show an opacity in the right lung that progressively clears to result in a hyperexpanded right lung that causes compression of the adjacent lung and contralateral mediastinal shift by 6 months. Chest radiograph at 2 years of age reveals a hyperexpanded right hemithorax with widening of the intercostal spaces and leftward mediastinal shift.

References

Berrocal T, Madrid C, Novo S, Gutiérrez J, Arjonilla A, Gómez-León N. Congenital anomalies of the tracheobronchial tree, lung, and mediastinum: embryology, radiology, and pathology. Radiographics. 2004 Jan-Feb;24(1):e17.

Gliomatosis Cerebri

Gliomatosis cerebri is a rare diffuse and infiltrative glial neoplasm involving at least two lobes of the brain. It is frequently bilateral and is typically a white matter process.

T2-weighted images typically reveal a homogeneously hyperintense infiltrating mass with mild mass effect on adjacent sulci and ventricles. Minimal or no enhancement is typical (foci of enhancement may represent anaplastic components). Pre-contrast T1-weighted images may reveal an iso- or hypo-intense process. DWI images usually reveal no restricted diffusion. Spectroscopy may reveal marked elevation of the myoinositol peak.

The main differential considerations include:

• Vasculitis: Usually more patchy; however, biopsy may be needed in some cases.
• Viral encephalitis: More acute presentation.
• Anaplastic astrocytoma: May present as an infiltrating process, but is not often diffuse. Enhancement is variable.

Other entities usually included in the differential can be distinguished by their enhancement pattern or distribution.

References

• Freund M, Hähnel S, Sommer C, Martmann M, Kiessling M, Tronnier V, Sartor K. CT and MRI findings in gliomatosis cerebri: a neuroradiologic and neuropathologic review of diffuse infiltrating brain neoplasms. Eur Radiol. 2001;11(2):309-16.
• Guzmán-de-Villoria JA, Sánchez-González J, Muñoz L, Reig S, Benito C, García-Barreno P, Desco M. 1H MR spectroscopy in the assessment of gliomatosis cerebri. AJR Am J Roentgenol. 2007 Mar;188(3):710-4.

Bronchial Carcinoid Tumor

Bronchial carcinoid tumors are uncommon neuroendocrine neoplasms of the lung, comprising less than 2% of all lung tumors. Carcinoid tumors are considered malignant, with potential for metastasis. They may fall in the spectrum of small cell carcinomas, with low-grade carcinoids on one end and small cell carcinomas on the other. A recently described large cell neuroendocrine variant (intermediate cell neuroendocrine carcinoma) falls between atypical carcinoids and small cell carcinoma of the lung. Like their gastrointestinal counterparts, they can secrete serotonin, adrenocorticotropic hormone, somatostatin, and bradykinin.

Carcinoids can be broadly defined as typical and atypical, with the former having a better prognosis. Imaging features can be similar and depend mainly on location. The vast majority (80%) of bronchial carcinoids are central and are found in the main, lobar, or segmental bronchi, presenting as hilar or perihilar masses with or without obstructive symptoms. The remainder present as peripheral nodules.

Different calcification patterns have been described, with eccentric calcifications more commonly seen. Diffuse calcification of the tumor can simulate broncholithiasis.

Post-contrast images typically (though not invariably) reveal marked, homogeneous enhancement, consistent with the highly vascular nature of these tumors.

Hilar or mediastinal adenopathy can be seen, reflecting either metastasis or reactive adenopathy from obstructive pneumonia.

Central carcinoids

Central carcinoids typically have an endobronchial component, with possible extension into adjacent parenchyma. Tumors with a dominant extraluminal component are referred to "iceberg lesions," while smaller tumors confined completely within the bronchus can also be seen.

The typical appearance of a central bronchial carcinoid is a well-defined, round or ovoid hilar or perihilar mass. Lobulated, irregular or ill-defined margins can also be seen. Mediastinal extension and multifocal disease is rare.

Because of the obstructive nature of central carcinoids, patients may present with recurrent atelectasis and pneumonia (this was the presentation of our patient). Contrast-enhanced CT is useful in differentiating an enhancing carcinoid from adjacent atelectasis, consolidation, and mucoid impaction.

Peripheral Carcinoids

A bronchial carcinoid can present as a solitary pulmonary nodule in about 20% of cases. These nodules are usually round or ovoid with smooth or lobulated borders. Atypical carcinoids are more likely to occur in the lung periphery

Other Imaging Findings

Carcinoids are T2-hyperintense, octreotide-avid, and typically negative on FDG. MIBG and octreotide are of similar sensitivity and specificity in detecting liver metastases, and some carcinoids not seen on octreotide imaging may have MIBG uptake.

Differential Diagnosis

• Adenoid cystic carcinoma
• Mucoepidermoid carcinoma
• Benign mesenchymal neoplasm

References

Jeung MY, Gasser B, Gangi A, Charneau D, Ducroq X, Kessler R, Quoix E, Roy C. Bronchial carcinoid tumors of the thorax: spectrum of radiologic findings. Radiographics. 2002 Mar-Apr;22(2):351-65.

Upper Extremity Arterial Occlusive Disease

Causes of upper extremity arterial occlusive disease

• Central embolic disease: Cardiac origin. Most commonly lodge in the brachial artery.
• Acute trauma:
• Hypothenar hammer syndrome: Repetitive trauma to the hypothenar area. Angiography may reveal focal ulnar artery aneurysm at the level of the hamate with segmental palmar ulnar artery occlusion and multiple digital artery occlusions. May also see the characteristic corkscrew elongation and ectasia of the ulnar artery. The superficial palmar arch is more often affected, but the deep palmar arch can also be involved.
• Thoracic outlet syndrome: Due to compression of the subclavian artery at the thoracic outlet, which may result in localized atheroma or aneurysm with embolization.
  
  
• Large and medium vessel vasculitis: Takayasu arteritis and giant cell arteritis. Involve large inflow and medium size proximal outflow arteries.
• Medium and small vessel vasculitis: Buerger disease (can also involve upper extremity veins), Behcet disease.
• Small-vessel vasculitis: Rheumatoid arthritis, Sjögren syndrome, Wegener granulomatosis, polyarteritis nodosa, scleroderma, systemic lupus erythematosus, polymyositis, dermatomyositis, mixed connective tissue disorders.

References

• Hellinger JC, Epelman M, Rubin GD. Upper extremity computed tomographic angiography: state of the art technique and applications in 2010. Radiol Clin North Am. 2010 Mar;48(2):397-421, ix.
• Maiman MH, Bookstein JJ, Bernstein EF. Digital ischemia: angiographic differentiation of embolism from primary arterial disease. AJR Am J Roentgenol. 1981 Dec;137(6):1183-7.

Oligodendroglioma

Oligodendrogliomas, the third most common glial neoplasms, are diffusely infiltrating, well-differentiated, slowly growing tumors. They are round or oval and involve the cortex or subcortical white matter. They typically contain calcifications (80% of cases) and most commonly affect the frontal lobe.

on CT, they present as mixed attenuation cortically based lesions with nodular or clumped calcifications. Cystic degeneration is seen in about 20% of cases. Bone windows may reveal expansion, remodeling or erosion of bone. There is variable enhancement and little to no surrounding edema.

The lesions are heterogeneously hypointense to isointense to gray matter on T1-weighted images and demonstrate cortical expansion. T2-weighted images reveal minimal associated edema surrounding a heterogeneously hyperintense mass. Low signal areas correspond to calcium (common) or blood (seen in anaplastic types). No diffusion restriction is typical for these lesions. Oligodendrogliomas typically demonstrate variable and heterogeneous enhancement.

References

Koeller KK, Rushing EJ. From the archives of the AFIP: Oligodendroglioma and its variants: radiologic-pathologic correlation. Radiographics. 2005 Nov-Dec;25(6):1669-88.

Spotted Spleen

A spotted spleen, one with multiple low-attenuation nodules, is an uncommon finding that can be seen with:

• Tumor: Lymphoma (most common), metastases, hemangioma (most common benign splenic tumor).
• Infectious: Fungal, mycobacterial (tuberculosis shown above), or parasitic. More frequent in immunosuppressed patients.
• Inflammatory: Sarcoid is the most common

References

Warshauer DM, Molina PL, Worawattanakul S. The spotted spleen: CT and clinical correlation in a tertiary care center. Comput Assist Tomogr. 1998 Sep-Oct;22(5):694-702.