NBME 16 Pulmonary small cell carcinoma metastatic to the brain (NBME Answers)

+1 upvote downvote
submitted by ∗bingcentipede(359)

get full access to all content ⋅ pick a username

The patient has a brain cancer, which is 50/50 between primary cancer and metastasis (lung most common; also breast, colon).

The answer is small cell carcinoma of the lung versus a primary brain cancer because there are cells staining positive for carcinoma marker (cytokeratin) and neuroendocrine markers (chromogranin and synaptophysin), which is what SCLC is.

get full access to all content ⋅ pick a username

cassdawg Another reason this is small cell lung cancer is the weakness of the proximal upper and lower extremities while also having augmentation (increasing) of strength with repetitive stimulation. This is characteristic of Lambert-Eaton myasthenic syndrome [where strength increases with stimulation; opposite of myasthenia gravis]. Lambert-Eaton can be caused by a paraneoplastic syndrome of small cell lung cancer (FA2020 p228 and 472) +18

passplease What about the fact that it is a single well-demarcated mass. Wouldnt metastatic cancer present as multiple masses? This made me think primary brain cancer. +10

jaeyphf @passplease I originally thought this way too and it fucked me. I think the easiest way is elimination + staining. Pt is an adult - eliminate neuroblastoma, ependymoma as both are more common in kids Pt is not immunocompromised - eliminate CNS lymphoma GBM does not stain positive for cytokeratin, chromogranin, synaptophysin - eliminate GBM Left with Small cell carcinoma +4

shieldmaiden @passplease Yeah I know! I basically came down to showdown of what was more likely and the metastatic small cell lung cancer won. The only thing a primary brain tumor had on its side as "unique" was that it was a solitary lesion, and that's just not enough. +1

hecticsurreyguy one thing to consider, and this is a long-ball, is the presence of left flank pain. Since the pain is localized to the left flank this makes me think that there is something wrong with the left kidney OR LEFT ADRENAL GLAND... We know that the adrenal glands most commonly receive mets from primary lung cancers, so taking this into account, this would further provide support that the brain met is from a lung cancer (pulmonary small cell carcinoma) and that this primary lung cancer is going to multiple locations. +