Radiology and Pathology Teaching PointsSessions I and II

Pat Hudgins and Dan Brat

I.1: Golden Grapes

A single image says it ALL!

• Swollen edematous ON– T2 information

• Expanded ON sheath– Good old symmetry!

• Dirty intraconal fat– Use of fat sat (FS) info

• Lack of flow void in SOV– MR physics: moving spins

should give signal void

I – Case 1

Diffusion Weighted Imaging (DWI)

• Add diffusion gradients

• ↑ signal intensity (SI)– Real: √ ADC map– Artifact: T2 shine

through

• ADC map – dark

• True restricted diffusion

I – Case 1

Diffusion Weighted Imaging (DWI)

• Infarcted brain

• Pus

• Rare acute MS plaque

• Some high grade BT’s

• Some neoplasms

• Creuztfelt Jakob

• Misc infections

I – Case 1

• “Pus” is THE SHORTEST pathologic diagnosis (Purulent material is more appropriate)

• Stains for bacteria are NOT helpful for speciation

• When infectious disease is on the differential, specimen should be sent to Microbiology for cultures

I.2: Ain’t No Sunshine When You are Gone! 

“T1 Ax Gd FS “I – Case 2

Imaging TechniquesPulse Sequence “Families”

Spin Echo Gradient Echo

I – Case 2

Fast Imaging Techniques

Siemens MP-RAGE VIBE

General Electric 3D Fast SPGR LAVA-XV

Philips 3D TFE THRIVE

I – Case 2

Fast Imaging Techniques

Gradient Echo – “Fast” Imaging

MP-RAGE

Magnetization Prepared Rapid Acquisition Gradient Echo

• 3 D, can do multiplanar reformats

• Isovoxel 1 mm x 1 mm x 1 mm

I – Case 2

Fast Imaging Techniques

Gradient Echo – “Fast” Imaging

Might look like a T1, but be careful

Disadvantages• Metal artifact is bad• WM very bright – can obscure

enhancing lesions• Cranial nerves often “enhance”

I – Case 2

Pilocytic Astrocytomas (grade I) involve the optic pathways more frequently than Infiltrative Astrocytomas (grades II-IV)

Anaplastic Astrocytoma (grade III) differs from grade II by the presence of mitoses and from Glioblastoma (grade IV) by its lack of necrosis.

Anaplastic Astrocytoma is generally fatal within 2-5 years.

I.3: Some Orbital Confusion

Initial MRI: T1 A and C

• Do we see Stuff or a Thing?• Diff Dx for Stuff:

– Pseudotumor– Infection (but fat clean)– Sarcoid– Lymphoma– We’ll add to this list

during the next sessions as weird rare lesions are presented

I – Case 3

Motion and MRI = NOT GOOD!I – Case 3

T2 images take longer to acquire than T1Adding fat saturation ↑↑ time of acquisition

Bone Algorithm Makes Crappy Soft Tissue!

I – Case 3

If lymphoma is a possibility, send fresh tissue for flow cytometry.

Marginal zone lymphoma is one type of low grade B-cell lymphoma. MALTOMA is most frequent.

Distinguished from follicular, mantle cell and small cell lymphoma by morphology and markers.

 Antigen Status in

MZL

 CD20  Positive

 CD79a  Positive

 CD5  Negative

 CD10  Negative

 CD23  Negative

 CD43  Negative

 cyclin D1  Negative

I.4: A Wolf in Bear’s Clothing

Don’t underestimate CECT!I – Case 4

Gadolinium good, but over-rated!I – Case 4

Extramedullary Myloid Tumor and Chloroma are other terms

Remember Flow Cytometry!

Hematologic Malignancies can present in “liquid” or solid forms with identical cell types: Myeloid Sarcoma vs AML; SLL vs CLL

Myeloperoxidase expression is defining; also positive for CD68

Bone, soft tissue, skin and lymph nodes are most frequent sites

I.5: No Rhabdo?

CT vs MRII – Case 5

“Feathery” interface with intraconal fat implies intraconal extension!

Is the process intra-conal??I – Case 5

“Feathery” interface with intraconal fat implies intraconal extension!

MRI: T1 C Gd FS

• Fungal organisms (Zygomycoses, Aspergillus and Candida species) are readily identified in with silver stains

• Speciation based on stains is not generally advised.

• Send cultures

Session I: What have we learned?

1. In the right setting, DWI can change the dx!

Most MRI = anatomic, but DWI = physiology

2. Not every image with black CSF is true T1

Each new sequence has different limitations

3. Stuff vs thing = helps come up with DDx

4. Gd only one tool in the toolbox

5. A good CECT is another great tool

6. “Feathery” interface is intra-conal

Session I: What have we learned?

• If infection is a diagnostic consideration, send tissue for cultures; special stains are not optimal for speciation

• If hematologic malignancy is a diagnostic consideration, send tissue for flow cytometry and cytogenetics

• Both infiltrative and pilocytic astrocytomas can involve the optic pathways; pilocytics are much more frequent

II.1: Behind the Curtain

What can I say? Three separate lesions, should have been mets

Sometimes, you need a good pathologist!

II – Case 1

Pathologist’s view:Inflammatory pseudotumor is a non-satisfying diagnosis, usually one of exclusion

Mixture of chronic inflammatory cells and stromal response causing a mass (NOT “pseudo-”)

Combines many entities with variable outcomes

Unknown etiology; rule out lymphoma

II.2: Deaf and Dizzy. Have We Been Susacked?

Physiologic Imaging Trumps AnatomyII – Case 2

Physiologic Imaging Trumps AnatomyII – Case 2

• High grade B-cell lymphoma localized to vascular lumens

• Presents in the brain and skin most often• Multiple infarcts with variable distribution • Lymphoma unable to traverse blood brain barrier? • Dismal prognosis

Primary CNS Lymphoma Intravascular Lymphoma

II.3: It’s All In Your Head

“Stuff” differential got longer….II – Case 3

Histiocytoses Involving the CNS

CD68 S-100 CD1a Langerhans cell histiocytosis: + + +Rosai-Dorfman disease: + + -(sinus histiocytosis with massive emperipolesislymphadenopathy)Histiocytic sarcoma + - -Erdheim-Chester Disease + - -

lipid laden histiocytes with multinucleated cells

II.4: Is it Naughty or Nice?

If it looks like cotton…think MSII – Case 4

Stroke Demyelinating Disease

Most frequent cause of lawsuit in neuropathology is the misdiagnosis of demyelinating disease as a malignant astrocytoma

Macrophages are misinterpreted to be neoplastic astrocytes

Finding macrophages in a CNS biopsy should alert to non-neoplastic diseases, like MS or stroke (always atypical presentations)

CD68

II.5: A Difficult Bug to Swallow

T1 – Always look at anterior clinoidMets or meningioma

II – Case 5

Whole body PET not good for skull base

II – Case 5

Many patients present to medical attention with a metastatic carcinoma to the CNS without knowledge of a primary neoplasm.

Advances in imaging and immunohistochemical markers have made the search for a primary neoplasm much more successful.

TTF1/Napsin

Session II: What have we learned?

• Sometimes lesions don’t follow the “rules” Why did pseudotumor look like a thing?

• DWI is a great tool

• Erdheim-Chester likes the hypothalamus

• When you see cotton, think MS

• Orbital experts should use T1 images routinely, and put anterior clinoid process on your checklist!

Session II: What have we learned?

• Inflammatory pseudotumors are real diseases, but poorly understood and likely represent multiple etiologies.

• Intravascular lymphoma has similar malignant B-cells to primary CNS lymphoma, but trapped in blood vessels.

• Histiocytic infiltrates require subclassification based on morphology and markers.

• Fulminant cases of demyelinating disease can look like neoplasms radiologically and pathologically.

Have a Good Lunch

• Be back at 1PM

• We start promptly at 1:10PM