Ch. 2 - Benign tumors & cysts of the epidermis Flashcards
What is an acanthoma?
How can it be distinguished from reactive acanthosis?
A benign cutaneous neoplasm characterized by an expansion of the epidermis.
Rete ridge pattern is ablated in acanthomas.
How does the stratum corneum appear in seborrheic keratoses? What if they are inflamed or irritated?
Loose lamellar “shredded-wheat” stratum corneum.
If inflamed, SC looks compact, brightly eosinophilic, and parakeratotic.
What IHC and molecular markers are typical of seborrheic keratoses?
May express BCL-2.
Activating point muations in FGFR3.
Acanthotic seborrheic keratosis
Broad sheets of small polygonal keratinocytes with intervening horn cysts and loose lamellar keratin.
Often pigmented. Can be irritated or inflamed.
Hyperkeratotic seborrheic keratosis
Tall stacks of loose lamellar keratin with papillomatosis (“church-spire” appearance).
Reticulated seborrheic keratosis (adenoid seorrheic keratosis)
Thin pigmented interlacing downward extensions of the epidermis with reticular configuration of epidermis and horn cysts.
Solar lentigo
Thin pigmented interlacing extension of the epidermis. Shorter and more bulbous than reticulated SK and without horn cysts.
Diagnose: Multiple foci of reticulated seborrheic keratosis “hanging off” hair follicles. Comedo-like follicular infundibula.
Downling-Degos disease / reticulated pigmented anomaly of the flexures
Clonal seborrheic keratosis
Clonal islands of small keratinocytes within the epidermis with bland nuclei and no duct differentaition. May have horn cysts. No atypia!
Hidroacanthoma simplex
Clonal islands of small keratinocytes similar to clonal seborrheic keratosis but ducts in the clonal islands.
Bowen’s disease
Clonal islands of atypical keratinocytes, with atypia, buckshot scatter, and apoptotic cells. Overlying stratum corneum becomes parakeratotic.
Pigmented seborrheic keratosis
Pigment within keratinocytes; the SK can be acanthotic, hypekeratotic, reticulated, or clonal (pigment-restricted!)
Irritated seborrheic keratosis
Formation of squamous eddies within epidermis and presence of spindled keratinocytes. Overlying stratum corneum can become compact, eosinophilic, and parakeratotic.
Inflamed seborrheic keratosis
Lymphocytes and spongiosis. Overlying stratum corneum can become compact, eosinophilic, and parakeratotic. Overlying crust and lichenoid interface dermatitis may be present.
Melanoacanthoma
Acanthoma composed of small keratinocytes and pigmented dendritic melanocytes (most pigment within dendrites). Overlying stratum corneum is compact eosinophilic and parakeratotic.
Clear cell acanthoma (pale cell acanthoma)
Discrete acanthoma with clear cells (phosphorylase deficiency), overlying parakeratosis and a distinct transition to normal in the stratum spinosum. Neutrophiils.
Large cell acanthoma
Discrete acanthoma composed of cells with large nuclei, with overlying lamellar hyperkeratosis. Represents a heterogeneous group of lesions…
Inverted follicular keratosis
Endophytic lesions resembling an expanded hair follicle, with squamous eddies. Unrelated to HPV but multiple may mean Cowden’s syndrome.
Warty dyskeratoma
Endophytic lesion with acantholytic dyskeratosis and overlying parakeratotic crust.
Features corps ronds (round halo’d dyskeratotic cells) and grains (flattened basophilic dyskeratotic cells)
Acantholytic acanthoma
Acanthoma composed of bland keratinocytes with acantholysis. Resembles “dilapidated brick wall” of Hailey-Hailey disease.
Epidermolytic acanthoma
Often crateriform epidermolytic hyperkeratotic lesion. Thick granular layer with irregular granules.
Common epidermal nevus
(linear?)
Resembles seborrheic keratosis; typically present at birth (multiple associated with eye/CNS/MSK abnormalities).
Linear: Follows Blaschko’s lines, represents mosaicism, LOH, lyonization of X chromosome, or post-zygotic somatic mutation.
Inflammatory linear verrucous epidermal nevus (ILVEN)
Linear epidermal nevus with variable acanthosis, alternating ortho/parakeratosis, and gross erythema (not actually inflamed?)
Blaschkoid epidermolytic hyperkeratosis (EKH)
Resembles epidermal nevus but with epidermolytic hyperkeratosis. Represents mosaicism for keratins 1/10 (implicated in epidermolytic ichthyosis).
