CANCER OF UNKNOWN PRIMARY SITE (CUPS): AN APPROACH
Dowell JE. Cancer from an unknown primary site. Am J Med Sci. 2001l; 326: 35-46.
Hainsworth and Greco. Treatment of patients with cancer of an unknown primary site. NEJM 1993;329:257-263
Take home points:
1. Cancer of unknown primary site (CUPS) can be further identified and treated based on histologic type.
2. Immunohistochemical staining is important because it can identify potentially treatable cancers.
3. Use a systematic and evidence-based approach when confronted with CUPS.
First, some background:
• Cancers of unknown primary site (CUPS) account for approximately 5% of cancers.
• Patients present with symptoms that originate from the involved site of metastasis.
Initial evaluation including history, physical exam, and radiographic imaging fails to identify primary site.
Step 1: Sutton’s Law – go for the money (get some tissue).
• This step is implied, because you are dealing with a cancer of unknown primary site.
• Therefore, if you haven’t gotten tissue yet, get it because the histology is important.
Step 2: What is the histology of the CUPS?
• Histologic analysis of biopsy material separates CUPS into 3 types: adenocarcinoma (60%), poorly
differentiated (35%), and squamous cell carcinoma (5%).
Step 3: Based on the histology, follow steps to identify and treat the primary site.
- Primary site identified in only 15-20% of patients. Pancreas, hepatobiliary tree, and lung account for
40-50%. GI sites are also common. Breast and prostate only rarely present as CUPS.
- Immunohistochemistry can be used to diagnose prostate cancer (PSA stain) and thyroid cancer
(thyroglobulin stain). ER/PR stains are not specific
- Diagnostic testing: history, physical, abdominal CT, PET, serum PSA, mammography. Routine
radiologic or endoscopic evaluation that is not symptom-directed may be misleading. Tumor
markers are not useful diagnostically.
- Groups with specific treatment options: