Miliary Pulmonary Metastasis

Axial CT image shows multiple small 2-3 mm nodules (arrows) throughout both lungs in a patient with thyroid cancer.

Facts: Miliary Metastasis

• Uncommon form of pulmonary metastasis
• Most commonly due to thyroid cancer, renal cell carcinoma and melanoma

Pulmonary Metastasis in Thyroid Cancer

• Distant metastasis (lung and bone) found in 10-15% of patients with differentiated thyroid cancer
• Lung metastasis is most frequent in young patients with papillary carcinoma, and lungs are almost the only site of distant metastasis in children
• Variables found to be adversely affected survival: extensive metastasis, older age at metastasis, absent I-131 uptake of metastasis, and moderately differentiated follicular cell carcinoma

Our case: thyroid cancer with miliary metastasis

References:

1. Biersack HJ, Grunwald F. Thyroid cancer, 2nd ed, 2005.

2. Schlumberger MJ. Papillary and follicular thyroid carcinoma. N Eng J Med 1998;338:297-306.

Superficial Thrombophlebitis

Longitudinal US image of the antecubital fossa shows an echogenic clot in the basilic vein (arrows).

Facts: Superficial Thrombophlebitis

• Also known as superficial venous thrombosis
• Presence of thrombus in the lumen of superficial vein, followed by inflammation of the wall and adjacent tissues
• Variable degree of severity, can be in small venous tributaries but can extend into deep veins or, uncommonly, result in pulmonary embolism
• Related to Virchow's triad
• Prodromes of many systemic diseases (neoplasm, arteriopathy, collagen vascular disease) and syndromes (Trousseau, Mondor disease, Lemierre, Buerger disease)

Imaging

• Color Doppler US provides definitive diagnosis by showing clot, uncompressibility, absence of flow

Reference:

Sobreira ML, Yoshida WB, Lastoria S. Superficial thrombophlebitis: epidemiology, physiopathology, diagnosis and treatment. J Vasc Bras 2008;7. Available here.

C Sign of Talocalcaneal Coalition

Fig. 1: Lateral radiograph of the right ankle shows a C sign (yellow dotted line) that extends from the talar dome through the coalition component of the posterior talocalcaneal joint to the sustentaculum tali.
Fig. 2: Coronal reformatted CT image confirms the presence of talocalcaneal coalition (arrows) between the talus (T) and calcaneus (C).

Facts: Tarsal Coalition

• Abnormal bony, cartilaginous or fibrous articulation between two tarsal bones
• Congenital, caused by lack of bony segmentation
• Most common between calcaneus-talus and calcaneus-navicular
• Bilateral in 20% of cases

Imaging

• C sign seen on lateral view when middle facet talocalcaneal coalition is present (as in our case)
• Talar beak is an indirect sign of abnormal talonavicular motion, it is a bony spur from anterior superior aspect of talus
• CT is an excellent method to identify and characterize tarsal coalition

Reference:

Chew FS, Bui-Mansfield LT, Kline MJ. Musculoskeletal Imaging, 2003.

Renal Oncocytoma

Sagittal contrast-enhanced CT image shows a well defined, enhancing mass in the right kidney of a 67-year-old man presenting with hematuria.

Facts: Renal Oncocytoma

• 5% of all adult primary renal epithelial neoplasm in surgical series
• Believed to originate from or differentiate toward type A intercalated cells of the cortical collecting duct
• Men more common than women
• Frequently seen in 7th decade

Imaging Features

• Solitary, well defined mass of renal cortex
• Stellate fibrotic scar can be seen with large tumors
• Spoke-wheel pattern of feeding arteries seen on catheter angiography
• Cannot be differentiated from renal cell carcinoma, and can be associated with RCCs either as hybrid tumors or collision tumors

Our case: Oncocytoma proven by histology. On imaging, this mass cannot be differentiated from RCC and should be investigated as possible RCC until proven otherwise.

Reference:

Prasad SR, Surabhi VR, Menias CO, et al. Benign renal neoplasms in adults: cross-sectional imaging findings. AJR 2008;190:158-164

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Hematosalpinx

Fig.1: Sagittal US image of the pelvis of a 13-year-old girl presenting with acute pelvic pain shows multiple cystic lesions (arrows) behind the uterus (U). These cystic structures have peculiar frondlike structures internally suggesting that they represent a dilated fallopian tube.
Fig. 2: Sagittal T2W MR image confirms the presence of dilated fallopian tube with fluid-fluid levels, suggesting hematosalpinx.

Facts: What Causes Hematosalpinx?

• Tubal pregnancy (most common)
• Endometriosis
• Fallopian tube cancer
• Obstructed vagina resulting in menstrual blood backflow into fallopian tubes

Facts: Isolated Tubal Torsion

• Very rare entity causing lower abdominal pain
• Usually occurs in reproductive age
• Diagnosis rarely made preoperatively
• Imaging findings are adnexal cystic mass, hydrosalpinx, hematosalpinx
• Twisted fallopian tube, if visualized, is a specific sign for tubal torsion. If the ovary is also torsed, the ipsilateral ovary becomes enlarged.

Our case: isolated fallopian tube torsion causing hematosalpinx.

Reference:

1. Park BK, Kim CK, Kim B. Isolated tubal torsion: specific signs on preoperative computed tomography and magnetic resonance imaging. Acta Radiologica 2008;49:233-235.

2. Wikipedia: hematosalpinx

Endoleak after EVAR

Axial CT images of the same level during precontrast, arterial phase and delayed phase of enhancement show an endoleak at the right posterolateral aspect of the endovascular stent graft (arrow). The endoleak was visualized only in the delayed image. Aortic wall calcification noted in all images (arrowheads).

Facts: Endoleak

• One of the complications of endovascular aortic aneurysm repair (EVAR)
• Blood flow external to the stent-graft and inside the aneurysm sac
• Aneurysm sac communicates with the systemic circulation, most commonly, through reversal of flow through aortic branch vessels
• Difficult to diagnose and treat, management remains a controversy
• Classification system organizes endoleak into 5 types based on "source of blood flow"
• Most common type of endoleak after abdominal aortic aneurysm repair = type II, in which retrograde blood flow through aortic branch vessels into the aneurysm sac. Typical sources = inferior mesenteric and lumbar arteries.

Types of Endoleak

• I = attachment site leak (either proximal or distal)
• II = collateral-vessel leak
• III = graft failure - midgraft hole, junctional leak, or disconnect
• IV = graft-wall porosity
• V = endotension

Imaging Surveillance

• Lifelong imaging surveillance required after EVAR
• Ideal frequency not well defined, but usually done at 1 and 6 months after initial repair - then every 6 months thereafter
• CT angiography most widely used, multiphase is recommended
• Endoleaks have variable flow rates, therefore they can be detected at variable times after contrast administration. Some can be detected only on arterial phase or delayed phase (as in our case)

Reference:

Stavropoulos SW, Charagundla SR. Imaging techniques for detection and management of endoleaks after endovascular aortic aneurysm repair. Radiology 2007;243:641-655.

Posterior Mediastinal Mass

Fig. 1: Scout CT image shows a partially circumscribed posterior mediastinal mass (arrows) which was shown to be anterior to the spine on lateral scout view (image not shown).
Fig. 2: Axial CT image shows a mass to be entirely fat containing (arrows) located anterior to the spine, displacing the esophagus toward the left.

Facts: Posterior Mediastinal Mass

• Typical differential diagnostic approach utilizes the mass location on lateral view, whether it is projecting over the spine ("paraspinal") or anterior to the spine (but not over the heart)
• "Paraspinal" lesions have extensive differentials including neurogenic tumors, bone tumors (metastasis, myeloma), infection (abscess, discitis/osteomyelitis) and extramedullary hematopoiesis
• Lesions in another group have differential diagnoses of dilated esophagus, aorta (either unfolded, dilated or ruptured), hiatal hernia.

Our case: mediastinal lipoma

Reference:

Davies SG. Aids to Radiological Differential Diagnosis, 5th edition, 2009.

Spinal Hemangioma

Axial and sagittal reformatted CT images show a well circumscribe lytic lesion in the body of the thoracic spine with a "polka-dot" pattern (best appreciated on the axial image).

Facts: Spinal Hemangioma

• Most common benign lesions with a vascular origin
• In the spine, they are usually cavernous or mixed types
• Most common location = thoracolumbar or lumbar spine
• Can be seen in any age but most common after 40 years
• Mostly asymptomatic but can rarely cause compression fracture, spinal cord compression or nerve root encroachment

Imaging Findings

• Well circumscribe lytic lesion
• Internal thickened trabeculae (seen as "polka-dot" on axial view and vertical striation on reformations)
• On MRI, hemangiomas are hyperintense on both T1WI (likely due to fat component) and T2WI, with enhancement

Reference:

Herkowitz HN, Bell GR. The Lumbar Spine, 3rd edition, 2004.

Sphenoid Sinus Mucocele

Fig. 1: Axial unenhanced CT image shows opacification of the left sphenoid sinus due to a mass (arrow) causing slight expansion of the sinus. Some parts of the sinus wall are thin and some are thick.
Fig. 2: Coronal T2W GRE MR image show the mass to be very hyperintense. There was no contrast enhancement (image not shown).

Facts: Mucocele of Paranasal Sinus

• Most common expansile lesions of the paranasal sinuses
• Most common location = frontal, ethmoid
• Chronic, cystic lesion of the paranasal sinuses, lined by respiratory epithelium
• Results of obstruction of sinus ostium, causing accumulation of secretions into an expanding mass
• Contents are sterile. If it becomes infected, it is called mucopyocele
• Can be seen in any age group, commonly relapsed

Imaging Findings

• Complete sinus opacification
• Bone remodeling, expansion and thinning/thickening of the wall
• On fluid-sensitive MR sequence, it is very bright
• Differential diagnosis: mucus retention cyst (usually not filled the whole sinus and no expansion), polyp (common in nasal cavity)

Reference

Rollers CA. Mucocele of the paranasal sinuses. Available at URL: http://www.bcm.edu/oto/grand/05252000.html

Primary CNS Lymphoma (PCNSL)

Axial T2W and postcontrast T1W MR images show two enhancing intra-axial masses (arrowheads) in the right cerebral hemisphere, involving the deep white matter. The frontal lobe mass crosses the midline at the corpus callosum (arrow), and is in contact with the ependyma.

Facts: PCNSL

• Rare, 1% of all primary brain tumors
• Incidence is rising in both HIV and non-HIV groups
• Uncertain origin because the CNS does not have endogenous lymphoid tissue or lymphatic circulation
• Three populations at risk: organ transplant recipients, patients with congenital immunodeficiency syndromes and AIDS/other immunodeficiency

Imaging

• Masses in deep gray matter structures, periventricular region and corpus callosum
• Up to 75% of masses are in contact with ependyma
• Enhancing homogeneously
• Some surrounding edema but less pronounced than gliomas or metastasis
• Do not calcify, rarely hemorrhage
• Imaging differential diagnosis: glioblastoma, metastasis, sarcoidosis

Our case: primary CNS lymphoma, non-Hodgkin type, in a non AIDS patient.

Reference:

Atlas SW. Magnetic Resonance Imaging of the Brain and Spine, Volume 1, 4th edition, 2008.