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Pulmonology Quiz

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55 yr old presents with a 3 month history of cough and is found to have a 3 cm left upper lobe mass. CT scan of the chest, abdomen and pelvis is otherwise unremarkable.  Physical exam is without abnormality.  CT guided biopsy reveals moderately differentiated adenocarcinoma. TTF-1 is negative.

He has a history of cigarette smoking for 30 years, but quit 10 years ago.  He also has a history of colorectal cancer diagnosed 2 years ago and is s/p a low anterior resection.  Lymph nodes were negative at the time and he received no adjuvant chemotherapy or radiation.

Additional immunohistochemical stains reveal the cancer to be CK 7 positive, CK 20 negative, and TTF-1 positive.

Of the following options, which answer is most correct?

  1.  CK 7 positivity and CK 20 negativity supports a diagnosis of metastatic colorectal cancer
  2.  TTF-1 positivity supports a diagnosis of primary adenocarcinoma of the lung
  3.  TTF-1 negativity is uncommon in metastatic adenocarcinoma to the lung
  4.  CK 7 negativity and CK 20 positivity support a diagnosis of metastatic colorectal cancer to the lung