Answer for BIR CoW 22 Aug 2021
Pilocytic astrocytoma, WHO grade 1.
Findings
T1 hypointense, T2 hyperintense well circumscribed cystic lesion noted in left middle cerebellar peduncle with perilesional edema involving the left pons, midbrain and medulla.. Lesion suppressed in FLAIR, with no diffusion restriction. Lesion causes compression of the ipsilateral posterior part of midbrain, pons and 4th ventricle. On contrast, lesion shows peripheral rim of enhancement. Pilocytic astrocytoma in left middle cerebellar peduncle. HPE : Multiple sections studied show fragments of cerebellar parenchyma with adjacent fragments of neoplasm arranged in biphasic pattern. Foci of microcystic areas are seen alternating with compact fibrillary area. Scattered Rosenthal fibres and eosinophilic granular bodies are evident. Few congested blood vessels and areas of hemorrhage seen.
Discussion
Glioma is a non-specific term indicating that the tumor originates from glial cells like astrocytes, oligodendrocytes, ependymal and choroid plexus cells. Astrocytoma is the most common glioma and can be subdivided into the low grade pilocytic type, the intermediate anaplastic type and the high grade malignant glioblastoma multiforme (GBM). Childhood glioma are mostly infratentorial; Cerebellar and tectal plate astrocytomas are usually pilocytic astrocytoma, whereas most brainstem "gliomas" are the H3 K27M-mutant diffuse midline gliomas. Primary cerebellar peduncle lesions are defined as the ones that arise directly from the peduncle and spread to involve the neighboring cerebellum and brainstem vital areas.Tumors arising from cerebellar peduncle are extremely rare, behave aggressively, are invading in nature, and recur early. Tumor frequently extends beyond the enhancing part seen on imaging. Dissemination is believed to occur along ventricular wall and subarachnoid space. Malignant cerebellar peduncular lesions have poor overall survival despite surgical debulking. Considering the high leptomeningeal spread, role of craniospinal irradiation is well established. Pilocytic astrocytoma is a typically slow growing well-circumscribed tumor, often cystic. They are WHO grade 1 tumors. Commonly seen in children & young adults. Three common locations for pilocytic astrocytoma include cerebellar, opticochiasmatic-hypothalamic region and brainstem. Usually Cerebellar lesions are slowly growing neoplasms, appear as large cyst with mural nodule; Brain stem gliomas occur in pons & in 4th ventricle; Pontine lesions with infiltrative pattern causes CN nerve palsies, pyramidal tract signs, ataxia and have poor prognosis; Lesion around fourth ventricle present with hydrocephalus and they have good prognosis. In NECT scan PAs appear as a mixed cystic/solid or solid mass. Calcification occurs in 10-20% of cases. The most common pattern of enhancement is nonenhancing cyst with a strongly enhancing mural nodule. In MRI, Cystic PAs are well-delineated, appear hyperintense to CSF on both T1- and T2WI.They do not suppress completely on FLAIR. The mural nodule is iso-/hypointense on T1WI and iso-/hyperintense on T2WI. Solid PAs appear iso- or hypointense to parenchyma on T1WI and hyperintense on T2/FLAIR. Intense heterogeneous enhancement of the nodule in a cystic PA is typical. Enhancement of the cyst wall itself varies. A variant pattern is a solid mass with central necrosis and a thick peripherally enhancing "rind" of tumor. MRS in PAs often shows elevated Cho, low NAA, and a lactate peak—paradoxical findings in clinically benign-behaving tumor (Pseudomalignant Spectrum). pMR shows low to moderate rCBV. DIFFERENTIAL DIAGNOSIS: Pleomorphic xanthoastrocytomas Hemangioblastoma Ganglioglioma Cerebellar abscess/ hemorrhage Medulloblastoma Ependymoma TREATMENT: Surgical excision.
REFERENCES: Osborn’s Brain: Imaging, Pathology and Anatomy. Malignant cerebellar peduncle lesions ‑ rapid progression and poor outcome: Navneet Singla, Ankur Kapoor, Amey Savardekar , B. D. Radotra , Debjyoti Chatterjee , Sunil K. Gupta
Findings
T1 hypointense, T2 hyperintense well circumscribed cystic lesion noted in left middle cerebellar peduncle with perilesional edema involving the left pons, midbrain and medulla.. Lesion suppressed in FLAIR, with no diffusion restriction. Lesion causes compression of the ipsilateral posterior part of midbrain, pons and 4th ventricle. On contrast, lesion shows peripheral rim of enhancement. Pilocytic astrocytoma in left middle cerebellar peduncle. HPE : Multiple sections studied show fragments of cerebellar parenchyma with adjacent fragments of neoplasm arranged in biphasic pattern. Foci of microcystic areas are seen alternating with compact fibrillary area. Scattered Rosenthal fibres and eosinophilic granular bodies are evident. Few congested blood vessels and areas of hemorrhage seen.
Discussion
Glioma is a non-specific term indicating that the tumor originates from glial cells like astrocytes, oligodendrocytes, ependymal and choroid plexus cells. Astrocytoma is the most common glioma and can be subdivided into the low grade pilocytic type, the intermediate anaplastic type and the high grade malignant glioblastoma multiforme (GBM). Childhood glioma are mostly infratentorial; Cerebellar and tectal plate astrocytomas are usually pilocytic astrocytoma, whereas most brainstem "gliomas" are the H3 K27M-mutant diffuse midline gliomas. Primary cerebellar peduncle lesions are defined as the ones that arise directly from the peduncle and spread to involve the neighboring cerebellum and brainstem vital areas.Tumors arising from cerebellar peduncle are extremely rare, behave aggressively, are invading in nature, and recur early. Tumor frequently extends beyond the enhancing part seen on imaging. Dissemination is believed to occur along ventricular wall and subarachnoid space. Malignant cerebellar peduncular lesions have poor overall survival despite surgical debulking. Considering the high leptomeningeal spread, role of craniospinal irradiation is well established. Pilocytic astrocytoma is a typically slow growing well-circumscribed tumor, often cystic. They are WHO grade 1 tumors. Commonly seen in children & young adults. Three common locations for pilocytic astrocytoma include cerebellar, opticochiasmatic-hypothalamic region and brainstem. Usually Cerebellar lesions are slowly growing neoplasms, appear as large cyst with mural nodule; Brain stem gliomas occur in pons & in 4th ventricle; Pontine lesions with infiltrative pattern causes CN nerve palsies, pyramidal tract signs, ataxia and have poor prognosis; Lesion around fourth ventricle present with hydrocephalus and they have good prognosis. In NECT scan PAs appear as a mixed cystic/solid or solid mass. Calcification occurs in 10-20% of cases. The most common pattern of enhancement is nonenhancing cyst with a strongly enhancing mural nodule. In MRI, Cystic PAs are well-delineated, appear hyperintense to CSF on both T1- and T2WI.They do not suppress completely on FLAIR. The mural nodule is iso-/hypointense on T1WI and iso-/hyperintense on T2WI. Solid PAs appear iso- or hypointense to parenchyma on T1WI and hyperintense on T2/FLAIR. Intense heterogeneous enhancement of the nodule in a cystic PA is typical. Enhancement of the cyst wall itself varies. A variant pattern is a solid mass with central necrosis and a thick peripherally enhancing "rind" of tumor. MRS in PAs often shows elevated Cho, low NAA, and a lactate peak—paradoxical findings in clinically benign-behaving tumor (Pseudomalignant Spectrum). pMR shows low to moderate rCBV. DIFFERENTIAL DIAGNOSIS: Pleomorphic xanthoastrocytomas Hemangioblastoma Ganglioglioma Cerebellar abscess/ hemorrhage Medulloblastoma Ependymoma TREATMENT: Surgical excision.
REFERENCES: Osborn’s Brain: Imaging, Pathology and Anatomy. Malignant cerebellar peduncle lesions ‑ rapid progression and poor outcome: Navneet Singla, Ankur Kapoor, Amey Savardekar , B. D. Radotra , Debjyoti Chatterjee , Sunil K. Gupta
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!