note: In need of updating

Unknown Primary Cancer (Evaluation and Management)

Adenocarcinoma Metastatic to Neck

1. GENERAL CONSIDERATIONS

   1. General
      1. Adenocarcinoma is the most frequent light microscopic diagnosis (60%) in patients with carcinoma of unknown primary site (refers to entire body, not isolated to head and neck).
      2. It is typically found in elderly patients with metastatic tumor at multiple sites whose clinical course is dominated by symptoms related to metastases.
      3. Among those without identified primary site at the time of diagnosis, the primary site becomes obvious in only 15% to 20% of patients during life with 70% to 80% of primary sites identified at autopsy.
      4. Primary sites identified at autopsy
         1. Most common (40%): lung and pancreas
         2. Less common: gastrointestinal sites (stomach, colon, and liver)
         3. Rare: breast, prostate, ovary
   2. An exhaustive search for the primary site is generally not indicated because it rarely will be found and is not likely to have an impact on management.
      1. Exceptions
         1. Disease localized to neck potentially amenable to aggressive local therapy
         2. Disease process for which specific palliative therapy is available (ie, advanced prostate or breast cancer)

2. EVALUATION

   1. History and Physical Exam
      1. Include breast and prostate exam.
   2. Fine Needle Aspirate (FNA)
      1. Although immunohistochemistry may be done on FNA specimens, it may be insufficient to render a definitive diagnosis and may require an open biopsy.
   3. Open Neck Biopsy
      1. Confer with pathologists before biopsy so that specimen is processed correctly.
         1. Identify the possible need for touch preps, electron microscopy
         2. Consider immunohistochemistry for thyroglobulin (thyroid primary), receptors (breast cancer), PSA (prostate)
      2. The biopsy, if done under general anesthesia, should be done coincidentally with panendoscopy.
      3. The danger of disseminating distant metastases and developing increased risks of local recurrence is no longer felt to be sufficient to preclude this necessary diagnostic procedure.
      4. Plan incision to permit excision of scar along with future parotidectomy, neck dissection, or thyroidectomy as needed.
   4. Laboratory Tests
      1. CBC
      2. Liver function tests
      3. Serum creatinine
      4. Urinalysis
      5. Examination of stool for occult blood
      6. Males: serum PSA (prostate specific antigen)
   5. Radiographs
      1. CT of abdomen can identify a primary site in 10% to 35% of patients
      2. Chest CT (rule out lung primary)
      3. Direct evaluation according to symptoms
      4. "Extensive radiologic evaluation of asymptomatic areas is rarely useful... expensive and often results in confusing or false-positive information."
      5. PET scan may be used in initial evaluation if primary and extent of disease not otherwise identified.
   6. Endoscopy
      1. Flexible fiberoptic bronchoscopy should be done as an early study, especially with supraclavicular disease
      2. Panendoscopy (esophagus/nasopharynx/larynx) lower yield
      3. Consider gastrointestinal endoscopy: gastroscopy/colonoscopy

3. SUGGESTED READING

   1. Briasoulis E, Pavlidis N: Cancer of unknown primary origin. The Oncologist. 1997;2: 142-152.
   2. Hainsworth JD, Greco FA. Treatment of patients with cancer of an unknown primary site. N Eng J Med. 1993;329:257-263.
   3. Moertel CG, Reitemeier RJ, Schutt AJ, et al. Treatment of the patient with adenocarcinoma of unknown origin. Cancer. 1972;30:1469-1472.
   4. Neumann KH, Nystrom JS. Metastatic cancer of unknown origin: non-squamous cell type. Seminars in Oncology. 1982;9:427-434.
   5. Shildt RA, Kennedy PS, et al. Management of patients with metastatic adenocarcinoma of unknown origin: a Southwest Oncology Group study. Cancer Treat Rep. 1983;67:77-79.

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