Biological significance of congenital melanocytic Flashcards
CMN family, lifecycle, melanoma risk
CMN are classified into 2 broad groups. Name the groups.
- CMN blue type
- CMN non-blue type
CMN are classified into 2 broad groups. Which group is most common?
CMN blue type
Name 3 types of Nevi belonging to “CMN blue type” group:
- Mongolian spot
- Nevus of Ota
- Nevus of Ito
CMN of the “non-blue” family are also defined as _________ ____ .
Superficial CMN
Superficial CMN are divided into 3 groups by size. Name them.
- Small CMN (<2 cm)
- Medium CMN (2-20 cm),
- Large CMN (>20 cm)
Are Medium and large CMNs tumors or hamartomas?
Hamartomas.
Hamartomas are typified by a benign proliferation of melanocytes and keratinocytes
Which groups of CMN are always present at birth
Medium and large
Small CMN that present after birth are also known as _____ _________ _____ .
Early acquired nevi
Why are small CMN thought to belong to the family of CMN even when they present after birth?
Because of similarity in terms of
1. morphological features
2. behavior
Name Morphological features of Small CMN. Clinical and dermascopic.
Clinically: flat or slightly raised pigmented lesions
Dermoscopy: globular pattern
(Brown globules at the periphery is the hallmark of growing phase)
How do small CMNs evolve? Clinical and dermascopic.
Clinical: become more elevated and acquire a papillomatous or smooth surface.
Dermascopically: brown globules at the periphery disappear, while a cobblestone pattern becomes visible throughout the lesion.
(After a variable time, usually years)
What are the morphological features of medium and large CMN. Clinical and dermascopic.
Clinical: verrucous surface intermingled with terminal hairs. (Owing to keratinocytic proliferation)
Dermascopically: globular pattern, a reticular pattern or combination.
What is neurocutaneous melanosis
Rare, potentially life-threatening condition where CMN involve the central nervous system
When should you suspect neurocutaneous melanosis?
When large CMN is accompanied by multiple smaller CMN
(Satellitosis)
What investigation is mandatory in neurocutaneous melanosis
Brain MRI within first year of life
What is the usual lifecycle of small CMN?
- Tend to persist over time
- Undergo progressive maturation within the dermis
(May undergo spontaneous involution on nails and acral sites)
Overall risk of melanoma in patients with CMN.
In 1 of the largest studies including more than 6500 patient’s with medium and large CMN the overall risk of developing melanoma was …
0.7%
(at a median age of 7 years)
Risk of melanoma in patients with large CMN (> 40 cm).
In 1 of the largest studies are more than 6500 patient’s with medium and large CMN the risk of developing melanoma and CMN greater than 40 cm may reach ….?
10%
Risk of developing melanoma in an acquired melanocytic nevus …?
Approximately 1 in 200,000
Risk of developing melanoma risk in small CMN …. ?
Has not yet been calculated
The majority of melanomas arising in pediatric population develop in what type of nevus?
Small CMN
Although the risk is small, the number of small CMN greatly outnumber medium and large CMN.
What percentage of melanomas arising in pediatric population develop in CMN?
55%
What percentage of melanomas in the adult population arise de novo?
70%
Which is the most important melanoma precursor in terms of absolute numbers?
Small CMN
What is the difference between a tumor and a hamartoma?
- A tumor is a solid mass that forms when a group of abnormal cells clumps together.
(Tumors can be benign or malignant (cancerous)).
- The defining feature of a hamartoma is that the cells that clump together are the same as the cells found in the surrounding normal tissue.
(The normal cells in a hamartoma grow together atypically.)
