Cancer of Unknown Primary

Over at The Lands, we discussed cancers without a known primary source. Our own Dr. Dowell, program director of the Hematology/Oncology fellowship program wrote an excellent review of the topic – take a look at the summary below:

  • Clinical presentation: cancers of unknown primary site account for approximately 5% of cancers; patients typically present with symptoms that originate from metastatic lesions.
  • Diagnosis:
    • History, physical, abdominal CT, PET, serum PSA, mammography, and  symptom-directed radiologic or endoscopic evaluation.
    • Tumor markers are not useful diagnostically!
    • Tissue is the issue! Must get a biopsy from the most accessible site. Typically, the histology reveals adenocarcinoma (60%), poorly differentiated (35%), and squamous cell carcinoma (5%).
      • Adenocarcinoma: Primary site identified in only 15-20% of patients. Pancreas, liver/gallbladder, and lung account for 40-50%. Breast and prostate are rare. Immunohistochemistry can be used to diagnose prostate cancer (PSA stain) and thyroid cancer (thyroglobulin stain).
      • Poorly differentiated cancers:  immunoperoxidase staining can help to diagnose specific tumors like lymphoma, carcinomas (prostate, thyroid, neuroendocrine, germ-cell tumors), melanoma, and sarcoma.
      • Squamous cell cancers: if there is cervical lymph node involvement, primary tumor in head and neck should be sought with panendoscopy
  • Treatment: often, the disease severity or symptoms will require empiric therapy based on general area of the body that is involved:
    • Female with peritoneal mets: treat for epithelial ovarian cancer
    • Female with axillary lymph node mets: treat for breast cancer
    • Male with elevated PSA: treat for prostate cancer with hormonal therapy (androgen deprivation)
    • Cervical LAD: treat for locally advanced SCC of head and neck
    • Lower cervical or supraclavicular LAD: consider primary lung cancer and poor prognosis
    • Inguinal node LAD: primary site almost always identified (genital or anorectal) – treat accordingly
  • For more information on effective chemotherapy, check out chemoregimen.com

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