Author: Asim

Asim Bag • UAB, Birmingham, AL

Aunt Mickey (They Look the Same until You Undress Them). Posterior Fossa Tumor or Something Else?

51-year-old male with no significant past medical history presented with 3+ months H/O intermittent dizziness, intermittent headaches, difficulty going down stairs and 3+ days H/O tingling and numbness on the right side of face, right hand and foot. MRI revealed increased T2 signal and swelling of the entire pons including the middle cerebellar peduncles with effacement/obliteration of the prepontine and CP angle cisterns. Center of the lesion was heterogeneously T2 hypointense and showed heterogeneous contrast enhancement, small focus of diffusion restriction, focal area of increased CBV and high choline to creatine ratio (2.18) & a tall lactate peak on MR spectroscopy. Differential diagnoses at this point included metastasis, high-grade glioma, lymphoma and sarcoid.

FIGURE 1

FLAIR

T2

Postcontrast

Perfusion image

DWI with ADC

Spectroscopy

These were our differential diagnoses. Do you want to add any other differential diagnosis?

CT scan of chest, abdomen and pelvis were done in search of primary tumor. On CT chest, there were bilateral asymmetric hilar adenopathy and lower lobe predominant nodular densities. The overall chest findings were not typical for sarcidosis. Bronchoscopy-guided biopsy of the hilar nodes revealed non-caseating granulomas. CT of the abdomen and pelvis were unremarkable.

A diagnosis of sarcoidosis was presumed and the patient was put on steroids. Patient got better clinically and an MRI after 5 days revealed significant improvement of the T2 signal abnormality and mass effect. There was no appreciable change in the size of the enhancing lesion. Patient was discharged home with the diagnosis of sarcoidosis and was advised to continue steroids.

FIGURE 2

T2

Post contrast

2 weeks later the patient came back with new onset diplopia as a result of left 6th nerve palsy. MRI at this point showed interval enlargement of the mass, FLAIR abnormality and enhancement. Central T2 hypointense area was more heterogeneous. At …

Aunt Mickey (They Look the Same until You Undress Them). Meningioma or Something Else?

73 year old lady presented with six weeks history of odd behavior, increasing apathy, expressive aphasia, and mild headache. An MRI including diffusion and perfusion imaging was obtained. MRI revealed a T1 hypointense (to cortex) and slightly T2 hyperintense (to cortex) extra-axial mass in the left frontal region. There were multiple central T2 hyperintense areas. On post contrast T1 weighted sequence, there was intense enhancement of the mass except the central T2 hyperintense areas.There were prominent diffusion restriction and high rCBV in most parts of the tumor in diffusion and perfusion imaging respectively.

At this point, what is your diagnosis? Meningioma…… right?

Our pre-operative diagnosis was also meningioma. Only concern was that the diffusion restriction was little too much for a meningioma, even for a densely cellular anaplastic meningioma.

There were two surprises for us both from surgeons as well as from pathologists. When the surgeons opened the dura, the mass was intra-axial! When the pathologists saw the tumor under microscope, they found diffuse large B-cell lymphoma with very high proliferative index (90-95%) and officially they called it “Large B-cell lymphoma, diffuse, with high proliferative rate and intermediate features between Burkitt lymphoma and large cell lymphoma (WHO classification 2008)”.

This is a very interesting case because the tumor grew without following the ‘basic rules of neuroradiology’. Though the tumor arose from intra-axial compartment the way it enlarged and its internal morphology gave it a look of an extra-axial mass. This is not an uncommon dilemma of day to day neuroradiology practice. The best way to differentiate between pathologies at a given anatomic location is to execute a mental workout (I call it ‘Curé’s algorithm’) which is consisting of a) correct identification of the compartment from where …

Aunt Mickey (They Look the Same until You Undress Them). Meningioma or Something Else?

51 year old lady presented with headache and gait disturbances. An MRI including perfusion imaging was obtained. MRI revealed an extra-axial, dural based mass of the posterior fossa which was isointense to gray matter on T1 weighted sequence and hyperintense to gray matter on T2 weighted sequence. There was no diffusion restriction. On T2 weighted sequence, there was wedge shaped area of perilesional T2 hyperintensity extending transversely and superiorly to involve vermis. With contrast, the lesion showed intense homogenous enhancement. On perfusion study, there was considerable increase in rCBV. Preoperatively it was diagnosed as meningioma and the patient was scheduled for resection.

On surgery, the mass was encapsulated but the capsule was tightly adherent to the cerebellum. On histopathology, the tumor turned out to be a malignant fibrous histiocytoma (MFH) with 40% MIB-1 index.

MFH, the most common soft tissue sarcoma in adults, arises from fibroblasts, myofibroblasts or undifferentiated mesenchymal cells. Most patients are between 50 and 70 years old. Men are affected 2-3 times more commonly than women. Most MFHs arise de novo however, they can occur secondary to prior radiation, trauma, Paget’s disease, chronic osteomyelitis or benign bone tumors. MFH most commonly occurs in lower extremity. Head and neck area is involved up to 10% of cases.  In head neck, nasal cavity and paranasal sinuses are most commonly involved. It has variable appearances on CT and MRI. On CT, this is usually large lobulated sift tissue mass which is isodense to muscles with destruction/remodeling of adjacent bone. There may calcification in up to 5-20% of patients. On MRI, they are isointense to muscle on T1 weighted sequence and heterogeneously hyperintense on T2 weighted sequence. This tumor can have both solid and cystic component. Solid portion enhances intensely. Spontaneous hemorrhage is frequently seen and can obscure the primary tumor. …