What is the preferred systemic therapy regimen for a patient in their 40s with untreated metastatic sarcomatoid carcinoma of unknown primary, presenting with hepatic lesions, abdominal lymphadenopathy, and a lytic bone lesion?

1. Molecular phenotyping. Two of three of my patients with this presentation this year (lots of nodes, no primary) turned out to be melanoma. The other one probably has a sarcomatoid recurrence of his remote 2014 renal cell carcinoma. A melanoma patient gets just immunotherapy for this presentation. P...

Sarcomatoid carcinoma is a misnomer and is really a carcinoma with mesenchymal components, which make it more aggressive. Molecular typing is the best way to drive decision-making as it can give some idea of the sensitivity of the tumor (TMB, MSI, PD-L1, etc.). The IHC pattern may be helpful in dete...