Melanocytic lesions
Melanocytic lesions are commonly encountered in dermatopathology and an area which causes some difficulty, i.e. it is hard to decide in some cases whether a lesion is benign (e.g. Spitz nevus) or malignant (malignant melanoma).
Overview
Identifying melanocytes
- Pigmented.
- Clear cytoplasm.
Benign lesions
| Name | Clinical | Gross | Microscopic | Key feature | Image | |
| Lentigo simplex | < 40 years | small flat pigmented lesion | sender rete with melanocytes; no nests of melanocytes; no dermal melanocytes | no nests, epidermis only | [1] | |
| Junctional melanocytic nevus | usu. sun exposed skin, unusual in >50 years | small flat (uniformly) pigmented lesion | nests of melanocytes at tips of rete, no dermal melanocytes | nests in epidermis | [1] | |
| Compound melanocytic nevus | small slightly raised (uniformily) pigmented lesion | nests of melanocytes at tips of rete and in dermis; dermal melanocytes lack nucleoli, lack mitoses and "mature with depth" -- see Note 1. | benign nests in dermis & epidermis | [2] | ||
| Intradermal melanocytic nevus | Clinical DDx: fibroepithelial polyp (skin tag), basal cell carcinoma | raised, non-pigmented lesion | nested & individual melanocytes - only in dermis, +/- multinucleation, +/-pseudovascular spaces | nested & individual melanocytes - only in dermis | [2] | |
| Spitz nevus (epithelioid and spindle-cell nevus) | Children & adolescents | usu. non-pigmented | spindled, epithelioid or mixed melanocytes, long axis of nests perpendicular to surface, superficial mitoses common | long axis of nests perpendicular to surface | Spitz nevus (drmihm.com) | [2] |
| Pigmented spindle cell nevus of Reed (AKA Pigmented spindle cell nevus) | women in teens & 20s; location: shoulder, pelvic girdle region | Pigmented +++, small size | heavily pigmented spindle cells in epidermis & dermis, form "basketweave" pattern, nests (???) | nests of heavily pigmented spindle cells | Reed nevus - collection of images (histopathology-india.net) | [3] |
| Blue nevus | usu. head & neck or extremities | blue flat or slightly raised lesion | dermal lentil-shaped nests, mix of spindle or dendritic or epithelioid cell morphology, nests btw collagen | lentil-shaped (ovoid) nests btw collagen bundles | Blue nevus (WC) | [4] |
| Cellular blue nevus | congenital or acquired; usu. scalp or butt | blue flat or raised lesion | deep dermis; cells lack nucleoli; biphasic: (1) epithelioid cells with pale cytoplasm, (2) pigmented spindle cells +/- melanophages | dermal lesion with pigmented spindle cells & epithelioid cells | [4] | |
| Congenital-pattern nevi | congenital or acquired; large ones increased melanoma risk[5] | small, intermediate (2-20 cm) or large | extend along dermal structures (e.g. nerves, hair shafts, ducts); lacks atypia; +/-mitoses | growth along dermal structures | [4] | |
| Dysplastic nevus (Clark's nevus) | may be familial - precursor to melanoma | may have asymmetry in shape or pigmentation | melanocytes "bridges" btw sides of rete, "lamellar fibrosis" (collagen deep to epidermis), mod. atypia | melanocyte bridges, lamellar fibrosis | [6] | |
| Halo nevus | central zone of pigment | lymphocytes at perimeter of melanocytic; epidermal melanocytes not nested; may be dermal, epidermal or both | lymphocytes +++ | [6] |
Note 1:
- "Maturation" in the context of melanocytic lesions means (1) the cells get smaller with depth, (2) cells are less mitotic with depth.
Spitz nevus
- AKA epithelioid and spindle-cell nevus.
Epidemiology
- Children & adolescents.
Microscopic
Features:[2]
- Architecture:
- Nests of cells (spindle, epithelioid or spindle/epithelioid) - in both dermis and epidermis.
- Nests are vertically arranged, i.e. the long axis of the nests are perpendicular to the skin surface.
- Nest arrangement/orientation described as "cluster of bananas".
- Nests are vertically arranged, i.e. the long axis of the nests are perpendicular to the skin surface.
- Nests of cells (spindle, epithelioid or spindle/epithelioid) - in both dermis and epidermis.
- +/-Hyperkeratosis (more keratin, i.e. thick stratum corneum).
- +/-Hypergranulosis (thick stratum granulosum).
- +/-Acanthosis (thick stratum spinosum).
- NEVER in the setting of solar elastosis.[7]
- If there is solar elastosis -- it's melanoma.
Images:
See also
References
- ↑ 1.0 1.1 Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 498. ISBN 978-0781765275.
- ↑ 2.0 2.1 2.2 2.3 Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 499. ISBN 978-0781765275.
- ↑ Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 500. ISBN 978-0781765275.
- ↑ 4.0 4.1 4.2 Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 501. ISBN 978-0781765275.
- ↑ Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson; Aster, Jon (2009). Robbins and Cotran pathologic basis of disease (8th ed.). Elsevier Saunders. pp. 1170. ISBN 978-1416031215.
- ↑ 6.0 6.1 Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 502. ISBN 978-0781765275.
- ↑ HJ. 16 July 2010.