Colorectal cancer metastasis mimicking medulloblastoma
History of one month headache and poor balance.
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A 3 x 4 cm irregular shape lesion is identified involving the left cerebellum and extending across mid-line. It is difficult to be certain as to whether the mass originated intra- or extra-axially. It certainly has an intraxial component with extensive oedema, but also has abuts the dura over a large area.
The lesion is heterogeneous on T1 with areas of low signal on T2 suggesting haemorrhage. Extensive high T2 surrounds the lesion in keeping with oedema. No restricted diffusion on DWI.
Following administration of contrast the lesion has a well defined enhancing edged but hypointense centre suggesting necrotic centre.
The 4th ventricle is distorted with evidence of obstructive hydrocephalus and tonsilar herniation.
3 case questions available
The patient went on to have a craniotomy and excision of the mass.
Sections from specimens A, B and C show a moderately well differentiated adenocarcinoma demonstrating a garland-like pattern of infiltration with peripheral cribriform and glandular architecture and central large areas of necrosis. The tumor is well demarcated from the adjacent cerebellar tissue. The neoplastic cells show distinct cell membranes, eosinophilic cytoplasm and pleomorphic nuclei with frequent mitoses. There is a moderate lymphoplasmacytic infiltrate in the desmoplastic stroma surrounding the tumor. Tumour cells are strongly positive for CK20 and CDX2 and negative for CK7, WT1, GCDFP, ER and PR
Final Diagnosis: Metastatic adenocarcinoma with morphologic and immunophenotypic features consistent with a primary colorectal carcinoma.
1 case question available
This is an unusual case in that the patient is young and presents with an aggressive looking near-midline cerebellar mass.