Episode 008: Metastatic Cancer of “Origin TBD”

Not to be confused with “carcinoma of unknown primary,” in this episode of metastatic disease of “origin TBD”, we discuss the workup of a mass noted incidentally on imaging.
This is a very high yield topic often faced on solid oncology consults!

Major Points Covered:

• Mass found incidentally on imaging → we need to stage always

• Initial Workup:

  • Reasonable to get CBC, CMP, UA, PSA (if male)

    • Low blood counts, maybe marrow involvement

    • Cr elevated concern for obstruction possibly

    • LFTs elevated concern for mass in the biliary/pancreas region

    • UA w/ hematuria → maybe bladder

    • But bottom line you’re gonna get a scan, which scan to get though?

  • Recommend referencing NCCN guidelines to determine additional staging scans

    • Create an account on nccn.org and look at guidelines by tumor type

    • Not all cancers require a PET/CT scan

    • There are newer modalities for imaging other than FDG PET including PSMA PET (prostate), Auxumin PET (prostate), and DOTATE PET (neuroendocrine)

    • Certain cancers can be diagnosed on imaging alone (RCC and HCC)

    • Some cancers require Brain MRI for staging

• What to biopsy?

  • FNA often adequate for solid tumors but may need core if non diagnostic

  • Need core or ideally excisional if highly concerned for lymphoma

  • Always try to biopsy the site that will upstage

    • Distant lymph nodes or other metastatic sites

• What about tumor markers?

  • We use this for treatment monitoring, not for diagnostic purposes

  • Important to establish a baseline to follow, special circumstances for diagnostic purposes to consider below:

    • PSA in male if concerned about prostate cancer

    • AFP helpful if concerned for HCC → liver masses in a cirrhotic

    • AFP and b-HCG if concerned for testicular → young or middle aged male with mediastinal mass

• Molecular testing not necessarily needed at the time of biopsy 

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