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Cerebral metastasis - solitary

Case contributed by Frank Gaillard
Diagnosis certain

Presentation

Seizure and headache.

Patient Data

Age: 55 years
Gender: Male

A lobulated heterogeneously enhancing lesion in the right temporal and occipital lobes, has a narrow base that abuts dura laterally and tentorium inferiorly, without a dural tail. No CSF cleft. Internal areas of T2 hyperintensity that are non-enhancing in keeping with either necrosis or cystic change. Small amounts of intrinsic T1 hyperintensity and susceptibility are also present. Moderate amount of surrounding FLAIR hyperintensity with some areas extending to involve cortex. MRS demonstrates primarily a lactate peak centrally and normal trace immediately adjacent to the lesion in the area of high T2 signal. CBV is elevated in the enhancing component.

Associated local mass effect, midline shift of 9mm to the left. Compression of the right occipital horn and trigone. Both temporal horns are slightly prominent with confluent periventricular FLAIR hyperintensity, some of which may represent transependymal edema. Right uncal herniation with mass effect upon the midbrain. 

A prominent vein drapes over the superior surface of the tumor without evidence of venous thrombosis. 

Conclusion: The differential is between high-grade diffuse glioma (GBM) or solitary metastasis. Presence of normal MRS and low CBV immediately adjacent to the lesion favors a metastasis. 

Case Discussion

The patient went on to have a resection and a staging CT of the chest and abdomen.

Histology

Paraffin sections show fragments of a moderately cellular epithelial tumor. This is composed of papillary and glandular structures lined by a stratified arrangement of columnar epithelial cells. These show moderate nuclear pleomorphism. Scattered mitotic figures are noted and there are several foci of tumor necrosis. Several of the glandular spaces are distended by mucinous material.

Immunohistochemistry shows moderate diffuse cytoplasmic staining in tumor cells for Napsin A and strong lumenal membrane staining for monoclonal carcinoembryonic antigen (CEA). No staining for estrogen receptor (ER), progesterone receptor (PgR), HER-2, TTF-1, CDX2, transthyretin or cytokeratins CK7 or CK20 is seen. 

Lung non-small cell carcinoma mutation testing:

  • EGFR NO MUTATION DETECTED
  • KRAS NO MUTATION DETECTED

FINAL DIAGNOSIS: cerebral metastasis - moderately differentiated adenocarcinoma 

CT of the chest and abdomen

CT of the chest and abdomen (not shown) demonstrated numerous liver metastases and mesocolon lymph node enlargement without an obvious primary although the colon did appear thickened. This was considered the primary tumor. The lungs and mediastinum were normal  

Discussion

It can be difficult to distinguish a solitary metastasis form a circumscribed high-grade glioma. If non-enhancing tumor (either on T2/FLAIR or ADC or MRS or CBV) can be detected then a diagnosis of high-grade glioma can be made with certainty. When no non-enhancing tumor is identified a metastasis is generally favored but needs to be weighed against pre-test probability. 

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