Chapter 25: Skin - Pigmentation/Melanocytes and Tumors Flashcards
A circumscribed, flat skin lesion distinguished from surrounding skin by color, either <5mm or >5mm in diameter describes what?
- Macules are <5mm
- Patches are >5mm
Elevated dome-shaped or flat-topped skin lesion, either <5mm across or >5mm across describes what?
- Papules = <5mm
- Nodule = >5mm
Surface elevation caused by hyperplasia and enlargement of contiguous dermal papillae describes what?
Papillomatosis
What is Parakeratosis and where is it a normal finding?
- Keratinization with retained nuclei in the stratum corneum
- Normal on mucous membranes
A traumatic lesion breaking the epidermis and causing a raw linear area (i.e., deep scratch) describes what?
Excoriation
Multiple trichilemmomas may be seen with what syndrome that is associated with an increased risk of endometrial cancer, breast cancer, and many other tumors?
Cowden syndrome –> loss-of-function in PTEN
Differentiate Freckles from Café au lait spots.
- Freckles: appear after sun exposure; fade and darken cyclically w/ season
- Café au lait: seen in neurofibromatosis; larger than freckles; arise independent of sun exposure
Linear (nonnested) melanocytic hyperplasia restricted to the cell layer immediately above the basement membrane that produces a hyperpigmented basal cell layer, describes what?
Lentigo
What is the histology of superficial nevi, deeper nevi, and the deepest nevi which are helpful in differentiating benign nevi from melanoma?
- Superficial: nests, large-round cells, ↑ melanin
- Deeper: cords or single cells, smaller, ↓ pigment
- Deepest: fusiform, fascicles resembled neural tissue
What is the clinical significance of spindle and epitheliod cell nevus (Spitz nevus)?
Common in children; red-pink nodule; often confused with hemangioma clinically
Clinically how do compound and dermal nevi differ in appearance from junctional nevi?
Often more elevated
Inheritance pattern of dysplastic nevus syndrome and chance of melanoma?
Autosomal dominant; >50% chance dev. melanoma by age 60
What are some of the distinguishing histologic features of dysplastic nevi?
- Typically larger than acquired nevi, >5mm, can be hundreds
- Lentiginous hyperplasia: single nevus cells replace basal cell at E-D jct
- Architectural and cellular atypia
- Lymphocytic infiltrate of superf. dermis, melanin incontinence
- Linear fibrosis surrounds epidermal rete ridges
Activating mutations in which downstream serine/threonine kinase from RAS is seen in 40-50% of melanomas?
BRAF
What is the most commonly mutated gene identified in melanomas?
↑ TERT expression (activation of telomerase)
In which growth phase of melanoma do tumor cells seem to lack the capacity to metastasize?
Radial growth –> horizontal spread of melanoma within the epidermis and superficial dermis
Melanomas in radial growth phase fall into what 3 clinicopathologic classes; which is most common?
- Lentigo maligna: usually indolent lesion on face of older men
- Superficial spreading: most common type of melanoma, usually involving sun-exposed skin
- Acral/mucosal lentiginous: melanoma unrelated to sun exposure
Which phase of melanoma growth is often heralded by the appearance of a nodule and correlates with the emergence of a tumor subclone with metastatic potential?
Vertical growth phase: tumor cells invade downward into deeper dermal layers as an expansile mass
Which feature of melanocytic nevi is absent from the deep invasive portion of melanoma?
Neurotization
Which measurement is the distance from the superficial epidermal granular cell layer to the deepest intradermal tumor cells; what does this correlate with in melanoma?
- Breslow thickness
- Depth of invasion correlates with probability of metastasis
Staining for which melanocytic marker can be useful in distinguishing melanoma cells?
HMB-45 (+)
Which nuclei and nucleolus findings are seen histologically with melanoma?
- Nuclei with irregular contours + clumped chromatin at periphery
- Prominent red (eosinophilic) nucleoli
What are 5 determinants of a more favorable prognosis with melanoma?
- Thinner tumor depth (Breslow thickness)
- NO (<1 per mm2) mitosis
- Brisk tumor infiltrating lymphocyte response
- NO regression
- Lack of ulceration
Where do most melanomas initially metastasize and how does this affect the clinical handling of these lesions?
- Regional lymph nodes
- Should perform sentinel lymph node biopsy; microscopic involvement of a sentinel node by even a small # of melanoma cells = worse prognosis
What are the ABCDEs of melanoma which correlate with the warning signs?
- Asymmetry
- Irregular Borders
- Variegated Color
- ↑ Diameter
- Evolution/change over time (esp. rapid)
*ANY pigmented lesion w/ diameter >6mm, any change, itching or pain*
Seborrheic keratoses may suddenly appear in large numbers as part of which paraneoplastic syndrome; associated with what malignancy?
Leser-Trélat sign; most commonly carcinoma of GI tract
Round, flat, coinlike, waxy plaques that are tan-brown describes what?
Seborrheic Keratoses
Which morphological feature is helpful in distinguishing seborrheic keratoses from melanoma?
Pore-like ostia impacted with keratin