True or false:
According to Elston, “crushing of the basal layer is less likely seen in melanoma.”
True
(See YouTube videoon Chapter 3)
What are the histologic findings of a fibroepithelioma of Pinkus? (4)
- Anastamosing pink strands with
- Eccrine ducts with
- blue buds at tips surrounding a
- fibromyxoid stroma
When evaluating the margins of a superficial BCC, where do you look? (2)
Aside from looking for tumor in the epidermis, make sure there is no tumoral fibromyxoid stroma at the margins in the dermis
What are histologic features of keratoacanthoma (KA)?
- Crateriform
- No acantholysis (an absolute disqualifier for KA)
- Hypergranulosis (beginning at hair follicles) toward the center of the lesion (whereas in SCCs, hypergranulosis is only at the lesion periphery)
- Amphophilic elastic fiber trapping (“KAs pull their way into the epidermis along elastic fibers”)
- Neutrophil microabscesses
- Eosinophils usually present (whereas plasma cells are more typically present in SCCs)
What does amphophilic mean?
That which can be stained with either an acid or basic dye (bluish-red color)
See Paget cells with abundant amphophilic, clear cytoplasm in image
What immunostains could you use to stain an invasive SCC? (5)
- Pankeratin
- p63 (nuclear stain)
- P40 (subtype of p63)
- AE1 and AE3 (mix of low- and high- molecular weight keratins)
- Keratin 903 (high molecular weight keratin)
What can the stain BerEP4 be used for?
A marker of BCC
What skin lesions have Pagetoid spread? (at least 4)
- Bowen’s disease
- Paget’s disease (PAS with diastase positive)
- Sebaceous carcinoma (EMA positive in a vacuolar pattern)
- Melanoma (S100)
What is trichilemmal keratinization?
Keratinizing abruptly WITHOUT a granular layer
What are the histologic findings of a proliferating pilar cyst (a.k.a. proliferating trichilemmal cyst or pilar tumor)?
Rolls and scrolls of keratinizing squamous epithelium
What is the “flag sign” for actinic keratoses?
Alternating ortho- and para-keratosis
Orthokeratosis appears at the acrosyringia and acrotrichia
Parakeratosis overlies the abnormal epidermis
Can sometimes be seen with Bowen disease
Where do you see the “eyeliner sign”? (2)
- Bowen’s disease
- Paget’s disease
What are the histologic features of micronodular BCC?
Palisaded blue islands with clear spaces
Round ovoid islands at the deep aspect that are between collagen bundles
When pagetoid spread “spits out” into the cornified layer, what two diagnoses may this suggest?
- Paget’s disease
- Melanoma
What is suggested by the following:
Cells spitting out into corneum
Crushing of basal layer
Amphophilic cells
Paget’s disease
According to Elston, how can you tell between a clonal SK and clonal Bowen’s disease?
- Look at the nuclear envelope (the single best discriminator)
- “In the squamous world, number of mitoses and pleiomorphism does not help you determine malignant or benign.”
- Malignant squamous cells may have a nuclear envelope that is thick, refractile, glassy, notched, and/or corrugated
- Benign squamous cells are oval and may have a delicate nuclear envelope (+/- multiple nucleoli, red nucleoli, or red mitoses)
Are acantholytic cells spindled?
“They tend to ROUND UP with acantholysis.”
Spindling usually requires desmosome attachments to stretch out the cell into a spindled shape.
What features may suggest HPV-induced (genital) Bowen’s disease?
Hypergranulosis
Compact horn with small, “cookie cutter” holes
Keratinocytes tend to be smaller than in other Bowen’s disease
What are histologic findings of infundibulocystic BCC? (3)
- Pink islands with blue buds
- Horn cysts
- Radiating outward from central follicular-like structures
What are the two “pink strand, blue bud tumors”?
- Fibroepithelioma of Pinkus (strands anastomose like a net with lumps of stroma in between)
- Infundibulocystic BCC (finger-like projections radiating outward into stroma)
How does the parakeratosis of an actinic keratosis versus a wart compare?
Actinic keratosis parakeratosis usually thin and flat
Wart parakeratosis is usually round
When trying to discriminate between Bowen’s disease and Paget’s disease, what stain for ducts may be useful?
Mucicarmine
Stains ducts and can visualize an underlying adenocarcinoma
What are the histologic findings of a trichoblastoma? (4)
- Lack of retraction space from stroma
- Palisading collections of blue cells
- Stroma is NOT fibromyxoid (which has a bluish hue and cell-poor) but instead is concentric and fibroblast-rich (like the follicular sheath)
- Papillary mesenchymal bodies in stroma
“The epithelium will look like a BCC but look at the stroma.”
What would be your stain choices for a desmoplastic SCC? (2)
- Keratin 903
- p63
- Note: pankeratin may be negative
