•52 year old man with no co-morbidities presented with history of generalised seizures . •Evaluated with MRI Brain which revealed multiple intra-axial lesions with characteristic imaging findings leading to the accurate diagnosis.
Case contributed by –
Department of Radio-diagnosis
Sri Shankara Cancer Hospital and Research centre, Bangalore ,India
•MRI brain reveals multiple intra axial T2 hypointense lesions marginated by T2 hyperintense rim encircling the lesion brighter than the surrounding edema with significant perilesional edema (Figure: A to C). It is evidently made in the lesion in the right parietal lobe (Arrows in Figure: C).
•Post contrast study demonstrates thick peripheral enhancement (Figure:F).
•DWI -ADC images demonstrating no restricted diffusion (Figure: D & E).
•Screening CT thorax demonstrates a large mass in the right lung lower lobe (Figure:G).
Final Diagnosis-•Intracranial-metastatic adenocarcinoma with pool sign
•Metastatic adenocarcinomas reveal themselves by exhibiting a perilesional T2 hyperintense rim immediately adjacent to the solid mass, deep to the peritumoral vasogenic edema.
•This T2 hyperintense rim appears to be pooling along the solid portion of the lesion, and is therefore referred to as the “pool sign”.
•It is higher in signal intensity relative to the vasogenic edema and is presumed to be secondary to secretions. “Pool sign” helps to focus the metastatic work-up on locations where adenocarcinomas are most common like lung and gastrointestinal tract. Any tumor that has secretory features, such as neuroendocrine tumor, could probably produce the “pool sign”. Cause of T2 hypointensity seen in intracranial metastatic adenocarcinoma (IMA) is probably due to T2 shortening caused by intralesional protein and mucin with abundant collagen. T2 hypointensity has high specificity and PPV for the diagnosis of IMA.
1.Cherian A, Divya K P, Prabhakaran PK, Jose J, Narayanan P, Thomas B. “Pool sign” in cerebral metastatic adenocarcinoma. Ann Indian Acad Neurol 2020;23:551-2.
2.Khunsa Faiz et al T2 Hypointensity Aids in the Diagnosis of Intracranial Metastatic Adenocarcinoma. Published online by Cambridge University Press: 17 December 2019