Investigation are done to see the 

1. extent of disease  
2. type of cancer  
3. patient’s fitness.

1. To See the Type of Cancer 

1. Histopathology: 

• pivotal in identifying the type of cancer and provides information that may direct subsequent management.

• Light microscopy

• Signet-ring cells favor a gastric primary.
• Presence of melanin favors melanoma
• Mucin is common in gut/lung/breast/endometrial and ovarian cancers.  
• Psammoma bodies are a feature of ovarian cancer (mucin +) and thyroid cancer (mucin -).

• Immunohistochemistry (IHC): SAQ (VVI)

1. Oestrogen (ER) and progesterone (PR) receptor positivity

→  indicate cancer may be sensitive to hormonal manipulation.  

1. HER2 receptor positivity in breast or gastric cancers

→ indicate tumor may respond to HER2 inhibitor targeted therapy.  

1. Alpha-fetoprotein (AFP) and human chorionic gonadotropin (hCG) 

→favor germ-cell tumors (GCT)

1. T-cell receptor (TCR) and cluster designation (CD) antigen expression 

→aid in the diagnosis and classification of lymphomas

• Molecular pathology

• EGFR mutations – predict response to EGFR inhibitor targeted therapy in lung cancer  
• RAS mutations – predict resistance to EGFR inhibitor targeted therapy in colon cancer  

• Cytogenetic analysis [ fluorescent in situ hybridisation (FISH) techniques]

• Can identify chromosomal changes
• Example: in Ewing’s sarcoma and peripheral neuro-ectodermal tumors → translocation between chromosome 11 and 22: t(11;22)