Central scar dilemma: Oncocytoma versus RCC

Case courtesy: SDIC, Bangalore

Central stellate non-enhancing scar, has been linked characteristically to oncocytoma. But unfortunately,

1. It is seen only in 1/3rd of oncocytoma cases, and renal cell carcinoma can also show those scars quite often. 
2. This patient was 55 yr old, which is a perfect age group for oncocytoma, yet renal cell carcinoma too have incidences in this age group only. 
3. Lesion appears well-encapsulated, and exophytic, which favour oncocytoma, yet medially capsule doesn't appear quite regular, and lesion appears infiltrative. 
4. Renal vein thrombosis may be seen in both RCC and oncocytoma, although not seen in this case.

In nutshell, radiology can give some good input, yet differentiating both is difficult. 5% of resected renal tumours turn-out to be oncocytoma. Yet, I favour diagnosing these kind of masses as renal cell carcinoma, as treatment of these masses should be surgical resection. Considering stage I renal cell carcinoma, renal sparing surgery may be thought in both the cases. Post-operative histopathology may bring some relief to patient if any, and improve prognosis if proven oncocytoma. Pre-operative prognosis is indeterminate.

(Case courtesy: Sapthagiri digital imaging center, Bangalore)

Aqueductal stenosis. CSF flow study could have proven beneficial.

What observation apart from hydrocephalus favour aqueductal stenosis? 

Flow void across aqueduct on T2 sagittal images, and upward bowing of corpus callosum. Detailed evaluation (not included) showed a dysgenetic corpus callosum, with markedly deficient body of corpus callosum.

Considering a congenital cause, what other morphological finding could have been seen?

Aqueductal web/diaphragm is sometimes seen. I feel there is a thin aqueductal web, even in this case.

Treatment of aqueductal stenosis:
Third ventriculostomy +/- VP shunting.

(Case courtesy: Sapthagiri Digital Imaging Center, Bangalore)

Avascular necrosis of femoral head

Arlet Ficat staging

Stage 0 – Normal

Stage 1 – Only marrow edema

Stage 2- Geographic defect (As seen in this case)

Stage 3- Crescent sign and eventual cortical collapse (Subchondral crescent in case, although no collapse).

Stage4- Secondary degenerative changes.

This case may be labeled Stage 2, progressing to stage 3.

Mitchell staging

CLASS A: Fat (T1 bright T2 intermediate)

CLASS B: Blood (T1 bright T2 bright)

CLASS C: Fluid (T1 hypo T2 hyper)

CLASS D: Fibrosis (T1 hypo T2 hypo)

This case appears class A.

Which bone is most common location of AVN?

Femoral head.

This Indian patient was a chronic alcoholic, travelled recently from middle east, with no history of recent acute trauma. What could be a likely predisposition of AVN in this patient?

Alcoholism is commonly associated with AVN.

Can you specifically guess, which arterial supply may be have been interrupted?

Most common artery involved is ‘lateral epiphyseal artery’, probably in this case too. Anterolateral femoral head is most commonly involved by AVN.

Do you see a ‘double line sign’ in this case?

Yes, at most anterior aspect of involved region.

 

(Case courtesy: Sapthagiri digital imaging center, Bangalore)

Right PICA territory infarct, with probably long-segment disease involving right vertebral artery.

What is a serious complication of these kind of infarcts?

These infarcts may not be clinically evident, and usually present at a later stage. PICA territory infarcts with long-segment involvement may carry a poor prognosis, due to gradual progression in mass effect, and brainstem involvement with hydrocephalus due to territorial progression or mass effect. Many-a-times, it needs a decompression craniotomy.

In the given case, is there an evidence of lateral medullary syndrome?

Yes, right lateral medulla is involved.

Which cerebral artery is most variable in its course, origin and distribution?

PICA is most variable cerebral artery. Approx. 20% arise from extracranial vertebral artery. Approx. 10% arise from basilar artery. In 2% of cases, they are bilaterally absent.