Genodermatoses and Nevi Flashcards

A congenital melanocytic nevus larger than 20 cm projected adult size is termed:

Answer: Giant congenital nevus

Congenital melanocytic nevi projected to reach ≥20 cm in adulthood are classified as giant, carrying the highest melanoma and neurocutaneous melanosis risk.

A halo nevus is characterized by:

Answer: A depigmented rim surrounding a melanocytic nevus

A halo (Sutton) nevus shows a rim of depigmentation from an immune response against nevus melanocytes.

The characteristic dermoscopic/histologic feature of a Spitz nevus can mimic which malignancy?

Answer: Melanoma

Spitz nevi have large spindled and epithelioid melanocytes that can histologically mimic melanoma, requiring careful evaluation.

A blue nevus derives its color from melanocytes located where in the skin?

Answer: Deep dermis (Tyndall effect)

The blue color results from the Tyndall effect as light scatters off melanin in deep dermal dendritic melanocytes.

Nevus sebaceus of Jadassohn most often occurs on the scalp and is associated with a somatic mutation in which gene?

Answer: HRAS

Nevus sebaceus commonly harbors postzygotic HRAS (or KRAS) mutations and can give rise to secondary neoplasms.

Multiple atypical (dysplastic) nevi plus melanoma in two first-degree relatives characterizes which syndrome?

Answer: FAMMM (familial atypical multiple mole melanoma) syndrome

FAMMM syndrome, often linked to CDKN2A mutations, features numerous atypical nevi and a strong familial melanoma risk.

A nevus spilus (speckled lentiginous nevus) appears as:

Answer: A tan patch studded with darker macules or papules

Nevus spilus is a background café-au-lait-like patch dotted with darker junctional or compound nevus foci.