Disorders of Pigmentation and Melanocytes Flashcards
Most common pigmented lesion of childhood?
Freckle
When does a Freckle arise?
AFTER sun exposure
Can Freckles fade or darken, if so, when?
Yes, with season changes
What spots are seen with Neurofibromatosis?
Cafe au lait spots
Cafe au lait spots are seen with what condition?
Neurofibromatosis
When do Cafe au lait spots arise?
INDEPENDENT of sun exposure
How do Cafe au lait spots compare to Freckles?
- Larger
- Contain aggregated melanosomes (macromelanosomes) in the cytoplasm of melanocytes
- Do not correlate with sun exposure
Lentigo
Benign localized hyperplasia of melanocytes
Benign localized hyperplasia of melanocytes
Lentigo
When is Lentigo initiated?
Childhood but occurs at all ages
How does Lentigo react when exposed to light?
(hyperplasia of melanocytes)
= Does NOT darken
How does Lentigo look on histology?
Linear melanocytic hyperplasia
Histologically, Lentigo is restricted to?
To cell layer immediately ABOVE basement membrane
What is restricted to the cell layer immediately ABOVE the basement membrane?
Lentigo
Linear melanocyte hyperplasia?
Lentigo
- Benign
A Melanocytic Nevus is a?
Mole
Mole
Melanocytic Nevus
Melanocytic Nevi are acquired by mutations in components of what signaling pathways?
RAS and BRAF
Melanocytic Nevi have activating mutations in RAS and BRAF that are only active for a limited time. What causes permanent growth arrest?
P16/INK4a cause permanent growth arrest
How do Melanocytic Nevi usually look?
Usually small <6mm, well defined borders and one color
Junctional Nevi
Nest at dermoepidermal junction
Type of Nevi that nest at dermoepidermal junction
Junctional Nevi
Compound Nevi
Nest in the epidermis and the dermis
Type of Nevi that nest in the epidermis and dermis
Compound Nevi
Intradermal Nevi
NO epidermal nests; usually older lesions
Type of nevi with NO epidermal nests
Intradermal Nevi - usually older
Describe how Melanocytic Nevi look from superficial to deeper tissues histologically
- Nests of large round cells
- Smaller, single cells
- Fusiform; fascicles resembling neural tissue
Superficial nests of large round cells that transitions into smaller cells and then into fascicles the deeper into the tissue suggests?
Melanocytic Nevi
Dysplastic Nevi have an increased risk of developing into?
Melanoma
Dysplastic Nevus Syndrome
> 50% chance to develop Melanoma by age 60
- Autosomal Dominant
What genes are mutated with Dysplastic Nevus Syndrome?
CDKN2A or CDK4
Those with Dysplastic Nevus Syndrome will likely develop?
Multiple dysplastic nevi and melanoma
Dysplastic Nevi acquire activating mutations in what pathways?
NRAS and BRAF
Histo - Dysplastic Nevi are ____ than acquired Nevi
LARGER
Histo - How do Dysplastic Nevi look?
Irregular borders with varied pigmentation and nests may coalesce
Histo - what cells will infiltrate superficial dermis with Dysplastic Nevi?
Lymphocytes
Histo - With Dysplastic Nevi, what surrounds the epidermal rete ridges?
Fibrosis
What is Shouldering?
Extension of junctional component beyond the dermal nests of melanocytes - corresponds to the periphery of lesion
What is Atypia and what is it seen with?
Irregular nucleus with hyperchromasia
- Dysplastic Nevi
What is the most deadly skin cancer?
Melanoma
Melanoma is usually caused by?
DNA damage due to UV light exposure
There is an increased incidence of Melanoma and decreased death. Majority of Melanoma cases are ____. What is a risk factor?
Majority are sporadic
- Severe sunburns early in life increases risk
Males usually get Melanoma where?
Upper back
Females usually get Melanoma where?
Legs
Blacks and Asians usually get Melanoma where?
Soles/Palms, nail beds, mucosal membranes
For Melanoma, what mutations will activate pro-growth signaling pathways?
RAS
BRAF
P13K/AKT
What is the most commonly mutated gene in Melanoma and what does it activate?
TERT
- activates Telomerase
What are the 2 growth phases of Melanoma?
- Radial growth
2. Vertical growth
The Radial growth phase involves horizontal spread of melanoma in the epidermis. What does it lack?
Lacks capacity to metastasize
The Vertical growth phase of Melanoma involves tumor cells invading down into deeper layers. What will likely appear?
Nodule with metastatic potential
What is absent in the Vertical Growth phase of Melanoma?
Neurotization
Breslow thickness
Depth of invasion - correlates with metastasis
Breslow thickness measures between?
Epidermal granular layer
Deepest tumor cell
- Correlates with metastasis
5 favorable prognoses for Melanoma
- Thinner tumor depth
- NO mitosis
- NO regression
- Lack of ulceration
- Brisk tumor infiltrating lymphocyte response
5 favorable prognoses for Melanoma
- Thinner tumor depth
- NO mitosis
- NO regression
- Lack of ulceration
- Brisk tumor infiltrating lymphocyte response