Principles and practice of Human Pathology – Lecture 1 + 2 (19-4-2018):
Pathology of primary skin tumors
Primary tumor: tumors that derive from the skin
Secondary tumor: tumors derived from another organ.
In both primary and secondary tumors you can have benign or malignant tumors.
Primary skin tumor:
Benign:
- No invasion of other tissue: limited to compartment of origin
- Name: tissue of origin + suffix ‘oma’, e.g. lipoma, angioma
Malignant:
- Local invasion
- Distant metastases can develop
- Name: tissue of origin + suffix ‘carcinoma’ or ‘sarcoma’
Mesenchymal = soft tissue, not epithelial derived.
Differences between benign and malignant tumors:
Benign:
- Normal chromosomal numbers/diploid
- Often slowly growing
- Cells without atypia
Malignant:
- Often rapid growth: mitoses
- Cells atypical
- Chromosomal abnormalities/aneuploidy
Histological diagnosis of tumors:
- Often simple with only microscope and simple H&E staining
If a tumor is malignant: the tumor will be excised.
Bread loaf technique: the way of processing a skin excision.
*The pathological assessment of a skin excision happens by means of microscopy.
Diagnosis of a tumor:
- Routine histology is sufficient in most cases (HE staining)
Sometimes additional techniques:
- Immunohistochemistry
- Molecular pathology
Immunohistochemistry:
- Usage of an antibody directed against an antigen on a tumor cell. The binding
is visualized with a chromogen.
, Cause of rising incident of melanoma:
- Aging
- Sun exposure (holidays)
- Tanning bed
*The most important thing you can do is prevention.
Most frequent primary malignant skin tumors:
1. Basal cell carcinoma
2. Squamous cell carcinoma
3. Melanoma
Melanoma is less frequent but much more aggressive than basal cell carcinoma and
squamous cell carcinoma.
Basal cell carcinoma (BCC):
- Really frequent
- Probably derived from hair follicle cells
o Therefore, not found on mucosa, palms and soles, because there is no
hair there.
- Frequent around eyes and nose.
- Only occurs in skin, not in other organs!!
Biological behavior:
- Locally aggressive
- Hardly ever metastasizes
o You will almost never die from a BCC.
Squamous cell carcinoma (SCC):
- Derived from keratinocytes
- Not really frequent
- Especially in areas with sun-exposition of long duration
- Can give rise to metastases: mostly nodal
- SCC can also develop in other organs with squamous epithelium (can be
primary or secondary)
o Therefore it is always important to think whether it is a primary tumor or
if it is derived from metastasis.
Cause 1: UVB;
- UV-specific mutations CC to TT mutations are found in tumor suppressor
genes (TP53, p16)
Cause 2: HPV
Cause 3: Immunesuppression
- E.g. with renal transplant recipients.
Cancer and genes:
1. Disease involving genes controlling cell growth and cell death
2. Clonal process: a tumor originates from a single progenitor cell that suffered
from genetic damage.
Pathology of primary skin tumors
Primary tumor: tumors that derive from the skin
Secondary tumor: tumors derived from another organ.
In both primary and secondary tumors you can have benign or malignant tumors.
Primary skin tumor:
Benign:
- No invasion of other tissue: limited to compartment of origin
- Name: tissue of origin + suffix ‘oma’, e.g. lipoma, angioma
Malignant:
- Local invasion
- Distant metastases can develop
- Name: tissue of origin + suffix ‘carcinoma’ or ‘sarcoma’
Mesenchymal = soft tissue, not epithelial derived.
Differences between benign and malignant tumors:
Benign:
- Normal chromosomal numbers/diploid
- Often slowly growing
- Cells without atypia
Malignant:
- Often rapid growth: mitoses
- Cells atypical
- Chromosomal abnormalities/aneuploidy
Histological diagnosis of tumors:
- Often simple with only microscope and simple H&E staining
If a tumor is malignant: the tumor will be excised.
Bread loaf technique: the way of processing a skin excision.
*The pathological assessment of a skin excision happens by means of microscopy.
Diagnosis of a tumor:
- Routine histology is sufficient in most cases (HE staining)
Sometimes additional techniques:
- Immunohistochemistry
- Molecular pathology
Immunohistochemistry:
- Usage of an antibody directed against an antigen on a tumor cell. The binding
is visualized with a chromogen.
, Cause of rising incident of melanoma:
- Aging
- Sun exposure (holidays)
- Tanning bed
*The most important thing you can do is prevention.
Most frequent primary malignant skin tumors:
1. Basal cell carcinoma
2. Squamous cell carcinoma
3. Melanoma
Melanoma is less frequent but much more aggressive than basal cell carcinoma and
squamous cell carcinoma.
Basal cell carcinoma (BCC):
- Really frequent
- Probably derived from hair follicle cells
o Therefore, not found on mucosa, palms and soles, because there is no
hair there.
- Frequent around eyes and nose.
- Only occurs in skin, not in other organs!!
Biological behavior:
- Locally aggressive
- Hardly ever metastasizes
o You will almost never die from a BCC.
Squamous cell carcinoma (SCC):
- Derived from keratinocytes
- Not really frequent
- Especially in areas with sun-exposition of long duration
- Can give rise to metastases: mostly nodal
- SCC can also develop in other organs with squamous epithelium (can be
primary or secondary)
o Therefore it is always important to think whether it is a primary tumor or
if it is derived from metastasis.
Cause 1: UVB;
- UV-specific mutations CC to TT mutations are found in tumor suppressor
genes (TP53, p16)
Cause 2: HPV
Cause 3: Immunesuppression
- E.g. with renal transplant recipients.
Cancer and genes:
1. Disease involving genes controlling cell growth and cell death
2. Clonal process: a tumor originates from a single progenitor cell that suffered
from genetic damage.
