Melanocytic lesions

From Libre Pathology
Jump to navigation Jump to search

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 slender 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 - low mag. (WC), Reed nevus - intermed. mag. (WC), Reed nevus - collection (histopathology-india.net) [3]
Blue nevus usu. head & neck or extremities; clinically confused with melanoma[4] 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), Blue nevus - very low mag. (WC), Blue nevus - intermed. mag. (WC) [5]
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 [5]
Congenital-pattern nevi congenital or acquired; large ones increased melanoma risk[6] small, intermediate (2-20 cm) or large extend along dermal structures (e.g. nerves, hair shafts, ducts); lacks atypia; +/-mitoses growth along dermal structures [5]
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 [7]
Halo nevus central zone of pigment lymphocytes at perimeter of melanocytic; epidermal melanocytes not nested; may be dermal, epidermal or both lymphocytes +++ [7]

Note 1:

  • "Maturation" in the context of melanocytic lesions means (1) the cells get smaller with depth, (2) cells are less mitotic with depth.

Dermal nevus

General

  • Think melanoma.

Clinical: ABCD = asymmetric, borders (irregular), colour (black), diameter (large).

Microscopic

Features:[8]

  • Symmetrical lesion.
  • "Matures" with depth - less cellular, less atypia.
  • No destruction of surrounding structures.
  • Only in dermis key feature.
    • Otherwise it is something else, e.g. dermal nevus, junctional nevus.

Microscopic

  • Basaloid cells mixed with squamous cells.
  • Keratin-filled invaginations.
  • Horn cysts - intraepidermal, brown globule-like structures.
    • Melanocytes at the dermoepidermal junction.[9]

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".
  • +/-Hyperkeratosis (more keratin, i.e. thick stratum corneum).
  • +/-Hypergranulosis (thick stratum granulosum).
  • +/-Acanthosis (thick stratum spinosum).
  • NEVER in the setting of solar elastosis.[10]
    • If there is solar elastosis -- it's melanoma.
  • Camino bodies (also written Kamino bodies) - dense eosinophilic bodies at dermoepidermal junction.[11]

Images:

See also

References

  1. ↑ 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. ↑ 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.
  3. ↑ 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. ↑ Mitchell, Richard; Kumar, Vinay; Fausto, Nelson; Abbas, Abul K.; Aster, Jon (2011). Pocket Companion to Robbins & Cotran Pathologic Basis of Disease (8th ed.). Elsevier Saunders. pp. 592. ISBN 978-1416054542.
  5. ↑ 5.0 5.1 5.2 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.
  6. ↑ 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.
  7. ↑ 7.0 7.1 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.
  8. ↑ need ref
  9. ↑ URL: http://emedicine.medscape.com/article/1059477-overview.
  10. ↑ HJ. 16 July 2010.
  11. ↑ URL: http://www.pathologyoutlines.com/topic/skintumorspitz.html. Accessed on: 18 May 2011.
Retrieved from "https://librepathology.org/w/index.php?title=Melanocytic_lesions&oldid=6916"