How to diagnose cancer in a clinic?

How to Diagnose Cancer in the Clinic

The diagnosis of cancer requires a systematic approach that begins with a thorough clinical evaluation followed by appropriate imaging and tissue confirmation through the least invasive method possible. 1

Initial Clinical Evaluation

History and Physical Examination

• Organ-specific symptoms: Bone pain, neurological symptoms, respiratory symptoms
• Non-specific symptoms: Fatigue, anorexia, weight loss
• Risk factors: Family history, smoking, occupational exposures
• Complete physical examination:
  • Head and neck examination
  • Breast examination
  • Rectal examination
  • Pelvic examination
  • Lymph node palpation
  • Skin inspection

Basic Laboratory Tests

• Complete blood count
• Liver and renal function tests
• Alkaline phosphatase and calcium
• Urinalysis
• Fecal occult blood test

Imaging Studies

Initial Imaging

• CT scan of the chest is essential for any patient suspected of having cancer 1
  • Helps define clinical diagnosis
  • Structures subsequent staging evaluation
  • Identifies potential biopsy sites

Additional Imaging Based on Clinical Presentation

• CT scan of abdomen and pelvis
• PET or PET-CT scan (superior to conventional staging tests) 1
  • Discloses previously unsuspected metastases in 6-37% of cases
  • More accurate for adrenal, liver, and bone metastases
  • Caution: PET-positive findings require clinical correlation and biopsy confirmation
• MRI for specific indications:
  • Brain metastases (superior to PET-CT) 1
  • Breast cancer evaluation in specific cases 1

Tissue Diagnosis

Approach to Biopsy

• Confirm diagnosis through the least invasive method possible 1
• Select biopsy site based on:
  • Accessibility
  • Safety
  • Likelihood of diagnostic yield

Biopsy Methods Based on Presentation

1. For accessible lesions:

   • Fine needle aspiration (FNA)
   • Core needle biopsy (preferred for breast lesions) 1

2. For lung lesions:

   • Bronchoscopy with transbronchial needle aspiration (TBNA) for central lesions
   • Endobronchial ultrasound-guided needle aspiration (EBUS-NA)
   • Transthoracic needle aspiration (TTNA) for peripheral lesions

3. For mediastinal disease:

   • Endoscopic ultrasound-guided needle aspiration (EUS-NA)
   • Mediastinoscopy if less invasive methods are non-diagnostic

4. For pleural effusions:

   • Thoracentesis (ultrasound-guided improves success rate) 1

5. For metastatic sites:

   • Biopsy of solitary metastatic site if feasible 1
   • For multiple distant sites, obtain diagnosis of primary lung lesion by least invasive method

Pathological Evaluation

Basic Pathology Assessment

• Histological type
• Grade
• Immunohistochemistry for specific markers

Special Considerations by Cancer Type

1. For suspected lung cancer:

   • Histologic evaluation and categorization 1

2. For unknown primary cancers:

   • Categorize into well/moderately differentiated adenocarcinomas, poorly differentiated carcinomas, squamous cell carcinomas, undifferentiated neoplasms, or neuroendocrine carcinomas 1
   • Apply immunohistochemistry in poorly differentiated cases 1
   • For adenocarcinomas: PSA testing in males, estrogen/progesterone receptors in females with axillary metastases 1
   • CK7/CK20 staining to suggest primary site 1

3. For breast cancer:

   • Core needle biopsy with ER, PgR, and HER2 receptor status 1
   • Ki67 labeling index for proliferation 1

Multidisciplinary Approach

• Involve multidisciplinary team early in the diagnostic process 1
• Include representatives from:
  • Pulmonary medicine
  • Thoracic surgery
  • Medical oncology
  • Radiation oncology
  • Palliative care
  • Radiology
  • Pathology

Common Pitfalls and Caveats

1. PET scan limitations:

   • False positives requiring tissue confirmation
   • Limited utility for brain metastases
   • Potential for incorrect upstaging (4.8% of cases) 1

2. Diagnostic delays:

   • Ensure timely and efficient delivery of care 1
   • Address barriers specific to local settings

3. Missed opportunities:

   • Maintain high index of suspicion for cancer in symptomatic patients 2
   • Consider alternative diagnoses when initial tests are negative

4. Verification bias:

   • Confirm positive imaging findings with tissue diagnosis 1
   • Be aware that PET-positive lesions may represent unrelated malignancies or benign disease

By following this systematic approach to cancer diagnosis, clinicians can ensure timely and accurate diagnosis, which is crucial for improving patient outcomes in terms of morbidity, mortality, and quality of life.