Chapter 6 Flashcards
What are the features of a solar lentigo?
Thin rete with bulbous tips “dipped in chocolate”
Note that reticulated SKs look similar have anastomosis of the rete ridges and horn cysts
What are the features of a melanotic macule?
Where are they found?
- Common on lips and genitals
- Rete are broad and squared off with pigment at basal layer
- May have strikingly irregular pigment if on genitals, but usually light brown and evenly pigmented
What is meant by maturation of melanocytes in a benign melanocytic nevus?
What should be ABSENT at the deep component of the lesion?
- Melanocytes become progressively smaller and spindled at deeper portions of lesion
- Deep mitoses should be absent
- Melanin should NOT be present in deep melanocytic nests, which can be confirmed by HMB-45 staining → loss of staining in deep component is a surrogate marker for maturation
- EXCEPT for blue nevi, which have pigment to the base of the lesion
In benign nevi, where are the junctional nests typically located? What about in a melanoma?
- Benign nevus → tips and sides of rete
- Melanoma → tops of dermal papillae are often involved as well
How can HMB-45 and MIB-1 be used to discern between a benign nevus and melanoma?
- Benign nevus → HMB-45 stains top heavy and MIB-1 does not stain deep nuclei
- Melanoma → HMB-45 commonly stains strongly to base and MIB-1 stains deep nuclei
What are the features of a balloon cell nevus?
- Balloon change is a degenerative feature caused by swelling of cellular organelles
- Usually sharply defined
- Well nested at DEJ
- Matures
- No deep mitoses or pigment
The nevic corpuscles of a neural nevus appear similar to what other structure?
“Little corn cob in dermal papilla that feels the lightest touch. They do not detect pain.”
What are the features of a neural nevus?
- S-shaped spindle cells similar to a neurofibroma
- Nevic corpuscles resembling Meissner corpuscles
- Sharply defined
- Matures
- No deep mitoses or pigment
What are the features of a congenital nevus?
- Look for aggregates about follicles, vessel walls, and nerves
- Patchy perivascular pattern of melanocytes
- Single-file interstitial pattern of melanocytes
What type of collagen composes Kamino bodies in Spitz nevi?
Type IV collagen
What should be the staining pattern visualized for a Spitz nevus with the following stains: HMB-45, S100A6, and MIB-1?
- HMB-45 → top-heavy
- S100A6 → stains diffusely
- MIB-1 → absent in melanocyte nuclei at base of lesion
What are the features of a “special site” nevus?
- May resemble a dysplastic nevus or have large junctional nests that are poorly cohesive (white space surrounding each melanocyte)
What are the features of an acral nevus?
- Nests are elongated and follow dermatoglyphs
- Buckshot scatter is OK at center of lesion
- Well nested at DEJ
- Matures
- No deep mitoses or pigment
What are the features of an ancient nevus?
- Large, hyperchromatic nuclei
- No confluent growth or expansile growth pattern
- No mitoses
- Sharply defined
- Well nested at DEJ
- Matures
- No deep pigment
What are the features of a halo nevus?
- Bandlike lymphoid infiltrate through lesion with lymphocytes and melanocytes mingling together “like a cocktail party” (as opposed to the “riot police” [walling off] of a melanoma)
What are the features of a blue nevus?
- Wedge or bulbous outline
- Pigmented to the base of lesion
- Melanocytes do not mature
- No deep mitoses
- Typically has a distinctive sclerotic, red stroma
What type of blue nevus is associated with Carney complex?
Epithelioid blue nevus
What are the features of a combined nevus?
Two or more populations of nevus cells
What are the features of a Wiesner nevus (benign BAPoma)?
- A unique type of combined nevus with a clone of combined nevus with a clone of epithelioid nevus cells embedded in a banal nevus
- Unlike Spitz nevi, the epithelioid population lacks vesicular nuclei, does not mature/disperse at base
- Hyperchromasia and pleomorphism common
- Boomerang nuclei cells present
- HMB-45 stains strongly to base (similar to melanoma)
- Strong p16 staining, loss of BAP-1 within clone
- Low MIB-1 (Ki-67) fraction
Weisner nevus (BAPoma) is associated with what familial syndrome?
Familial uveal melanoma/renal carcinoma syndrome
What are the features of a benign Clark nevus (dysplastic nevus)?
- Fading border or fried-egg appearance clinically
- Fading macular border corresponds to “shoulder” region
- Club-shaped hyperplasia of rete
- Horizontally oriented nests with bridging of adjacent rete
- Concentric papillary dermal fibrosis
- Large oval melanocytes, especially of shoulder region
- Matures
- No deep mitoses or deep pigment in nests
What are the features of a junctional lentiginous nevus?
- Club shaped epidermal hyperplasia
- Round/oval melanocytic nests at DEJ, and tips and sides of rete
What are the features of recurrent nevus (also known as persistent nevus or pseudomelanoma)?
- Confluent, poorly/irregularly nested junctional melanocytic proliferation
- Underlying scar
- Melanocytic proliferation confined to area overlying scar
- May see residual bland nevus under scar
What are the features of a nevus of Ota/nevus of Ito?
- Dendritic melanocytes scattered between collagen bundles in upper third of dermis
- Melanocytes oriented east to west
- No sclerotic stroma
- Nevus of Ota → face
- Nevus of Ito → shoulder
What are the features of a Mongolian spot (dermal melanocytosis)?
- Dendritic melanocytes scattered between collagen bundles in the lower half of dermis (as opposed to upper third like in a nevus of Ota/Ito)
- Melanocytes oriented east to west
- No sclerotic stroma
What are the features of melanoma?
- Poorly nested epidermal melanocytes
- Irregularly-spaced and -shaped nests not just at tips and sides of rete
- Areas of confluence
- May have adnexal extension
- Lack of maturation
- May have deep mitoses and pigment in nests
- Variable atypia
On a cytologic level, what are some signs of melanoma cells?
- Multiple nucleoli
- Peripheral nucleoli
- Clumped “peppered moth” chromatin pattern
- Solid hyperchromasia
- Epidermal consumption
- Parallel theque pattern at base of lesion
- Cells involve the arches of rete ridges (not just tips and sides) → see initial photo
What is the parallel theque pattern and what does it suggest?
Melanoma
What are the features of superficial spreading malignant melanoma?
- Buckshot scatter of atypical melanocytes within epidermis
- Nonnested melanocytes outnumber nests in areas
- Nests not confined to tips and sides of rete
- Lymphoplasmacytic infiltrate frequent at base (“riot police”)
- HMB-45 staining typically strong to base
- S100A6 typically patchy
- MIB-1 (Ki-67) staining of deep melanocyte nuclei common
What are the features of lentigo maligna?
- Broad lesion above solar elastosis
- Effaced rete ridges
- Extends down adnexae
- Nests not confined to tips and sides of rete
- Multinucleated giant cells (starburst giant cells) may appear at DEJ
What are the features of a spindle cell melanoma?
- Spindled cytology
- Most reliable immunostains are SOX100 and SOX10
Spindle cell neoplasms SLAMmed up against the epidermis include what?
- Squamous cell carcinoma (keratin positive)
- Leiomyosarcoma (smooth muscle actin positive, desmin positive)
- Atypical fibroxanthoma (diagnosis of exclusion)
- Melanoma (S100 positive)
What are the features of desmoplastic melanoma?
- Dense desmoplastic stroma
- Nodular lymphoid aggregates
- S100 or SOX10 (as in photo) are reliable, but HMB-45 is NOT
- Perineural extension common
Is desmoplasia hypo- or hyper-cellular?
Hypocellular
What are the features of “regressing melanoma”?
- Lichenoid regression may occur in lentigo maligna
- May appear as zones of fibrosis and melanophages
- Adverse prognostic indicator
- “Tumoral melanosis” → regressing melanoma
When metastatic melanoma occurs in lymph nodes, where in the lymph node does it occur?
Subcapsular
(Nodal nevi occur but are typically WITHIN the capsule.)
What are the features of clear cell sarcoma?
- Soft tissue tumor
- Clear cytoplasm
- Nuclear atypia
- S100 positive
- Characteristic chromsome location → t(12;22)(q13;q12)
