HC8: General principles: diagnostic pathology

Biopsies

A spiculated mass is a mass with spikes going into the surrounding tissue. Benign lesions generally don’t grow in this type of fashion → a biopsy needs to be taken.

Fine needle aspiration cytology:

FNAC stands for fine needle aspiration cytology:

1. A little bit of tumor is taken from the lesion with a needle
2. The tumor is spread out on a small glass
3. Color is added → rapid stain-RAL
   • This is a stain which takes 40 seconds

This isn’t a histology biopsy, because the cells are loose.

Visible cells:

Biopsies can be taken to test for breast cancer. Various cells become visible:

• Tumors
• Cells without a nucleus → erythrocytes
• Irregular cells vary in size

In a normal situation, the following is visible:

• Low cellularity
• Cohesive cell-groups
  • Cells are small and have the same size and shape
• Small cells
  • Maximal 1,5x the size of an erythrocyte

Signs of cancer cells are:

• Large, variably shaped nuclei
  • Hyperchromasia
    • The nucleus is darker
  • Polychromasia
• Many dividing cells → disorganized arrangement
  • Cells come loose from epithelia
• Variation in size and shape
  • Polymorphism
  • Pleomorphism
• Loss of normal features

Malignancy

Several important terms are:

• Benign: not harmful
• Malignant: harmful
• Atypia: a clonal proliferation
• Ductal carcinoma in situ (DCIS): not yet cancer
  • The cells look malignant, but this doesn’t actually prove that the lesion is malignant

A tumor is malignant when:

• Invasion occurs → malignant tumors recognize no anatomic boundaries
• Cells have the ability to metastasize → can invade blood and lymphatic vessels

Breast carcinoma:

A carcinoma can be invasive or in situ. Which of the 2 is the case cannot be seen on a biopsy:

1. Normal breast tissue is made of fat and duct
   1. Ducts transport milk to the nipple
   2. A duct contains an epithelial luminal layer which can transport and form the milk
2. When hyperplasia occurs in those ducts, the cell layer is proliferating within the duct
3. Atypia can occur in the proliferating cell population, which can lead to DCIS (ductal carcinoma in situ)
4. DCIS: the carcinoma is still in the duct and hasn’t travelled to a different location
   • DCIS cannot metastasize → isn’t a deadly disease
5. When the carcinoma travels somewhere else, it becomes an invasive ductal
   • Invasive ductals can metastasize

DCIS and invasive ductals cannot be distinguished on a microscopy slide → malignancy cannot be distinguished from carcinoma in situ. A core biopsy is necessary to do this. It also can be useful to palpate the lymph nodes in the axilla. Tumor cells in lymph nodes proof that the disease is malignant. An adenocarcinoma is a carcinoma in glandular tissue. It can metastasize in lymph nodes.

Macroscopical aspects:

Macroscopical aspects of malignancies are:

• Different from the surrounding normal tissue
• Solid and firm
• Poorly demarcated
  • Spiculated
  • Multinodular
  • Et cetera
• Necrosis (ischemia)
• Haemorrhage (bleeding)

Immunohistochemistry

Immunohistochemistry makes it possible to check whether a tumor is still in site:

1. Tissue is put on a slide
   • This tissue contains antigens
   • Tissue is put on a container filled with paraffin → very thin slices of paraffin are made
2. A primary antibody against the basal layer of the duct is added to the tissue
3. A secondary antibody with a color tag is added
4. The secondary antibody attaches to the primary antibody

If a stain which is only positive in the basal membrane of a duct is used, micro-invasion can become visible. This is the very early beginning of an invasive disease → the basal membrane is damaged. If the basal membrane is totally lost, malignant disease can be proved.

Hormones:

Tumors can use hormonal cycles to generate growth signals. On every breast cancer patient, additional staining is also done for:

• Estrogen receptors
• Progesterone receptors
• HER2 receptors

This can be used to choose the therapy → receptors can be blocked.

HER2:

HER2 stands for human epidermal growth factor receptor. These receptors are present on both normal and tumor cells, but on tumor cells in much larger numbers. The more receptors that are present on the cell, the more they are stimulated → the cell proliferates faster. This can happen via:

• Amplification: multiple HER2 genes
• Overexpression: many HER2 receptors

In case of HER2 3+, immunohistochemistry of a cell shows lots of brown, it means the whole surface of the cell is full of HER2.

Herceptin is a drug that blocks the HER2 receptor. It triggers a complete pathological response → the tumor stops growing and is cleared up.

Histology versus cytology

The biggest difference between histology and cytology is that histology shows tissue and cytology shows loose cells:

• Histology
  • Tissue
  • Cytonuclear atypia
  • Growth pattern
  • Invasion
• Cytology
  • Loose cells
  • Cytonuclear atypia
  • No context or growth pattern
  • Proving invasive growth in the primary tumor is difficult
    • Cytology from a lymph node with tumor cells does proof invasive growth

Removing a tumor

After removing a tumor, it needs to be proved that everything has been taken out → the site where it has been removed needs to be colored:

• When no interruptions are visible, everything has been completely taken out
• When there is a small interruption, the tumor hasn’t entirely been removed
  • The surgeon has to decide whether he wants to do a re-excision at that site 

Ink is used to make these margins visible:

• Cranial site
• Dorsal site
• Lateral sites 

A different color is used per site. Preferably, distance to margins needs to be >1 cm. This is a combination of macro- and microscopy.

Examples

Several images of tumors show:

• Image 1: benign, a cerebrally gland
• Image 2: benign, located in the uterus
• Image 3: malignant, located in the lung
• Image 4: malignant, on the skin → melanoma
• Image 5: malignant, in the testis → seminoma