Third ventricular metastasis
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Within the 3rd ventricle is a well-circumscribed enhancing mass which measures 22 x 31 x 22 mm. It is associated with oedema in the thalamus bilaterally, and seems to impede the outflow of the ventricles to some degree, as are temporal horns are slightly prominent, but without significant hydrocephalus. It is an isolated abnormality, with no other enhancing lesions seen elsewhere within the brain.
Conclusion: Third ventricular mass, in a patient with a large pulmonary mass and mediastinal nodes almost certainly represents a metastasis, presumably from a lung primary.
The patient went on to have a CT of the chest which demonstrated a large left upper lobe central tumour that measures 7 cm in size, encasing the left upper lobe bronchus and invading the mediastinum directly. There are several large upper mediastinal lymph nodes which measure up to 2.4 cm, but no enlarged subcarinal lymph node. The patient went on to have the chest lesion biopsied (transbronchial needle aspiration - TBNA).
MICROSCOPIC DESCRIPTION: The smears contain abundant malignant cells presenting singly, clusters and in sheets. The cells exhibit enlarged moderately pleomorphic nuclei, macronucleoli and large amounts of delicate, finely vacuolated cytoplasm. Abundant necrotic cellular debris is present in the background.
Immunoperoxidase staining shows the abnormal cells to be positive for TTF1 & CK7. The cells are negative for CK20, P63 & CK5/6. The immunophenotype is that of a primary lung adenocarcinoma.
FINAL DIAGNOSIS: Poorly differentiated adenocarcinoma.