SCC



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  • Histology

    • atypia
    • loss of maturation
    • dyskeratosis, squamous eddies/pearls, paradoxical maturation
    • invasion

  • Variants

    • desmoplastic SCC
      • nodular lymphoid aggregates
      • stain to find SCC hidden in stroma
    • verrucous carcinoma
      • well differentiated
      • blunt pushing border
      • distinguishing from a large verruca is subjective
    • spindle cell SCC
      • atypical spindle cells abutting epidermis
      • less keratinization, can be vimentin+
      • ddx mnemonic: SLAMmed up against epidermis
        • Squamous (keratin+)
        • Leiomyosarcoma (SMA+, desmin+)
        • Atypical fibroxanthoma (diagnosis of exclusion)
        • Melanoma (S100+)
    • adenoid SCC (acantholytic SCC, pseudoglandular SCC)
      • gland like changes but negative for mucin or CEA
    • adenosquamous SCC
      • goblet cells positive for mucin and CEA
    • lymphoepithelioma like carcinoma
      • dense lymphocytic nodules +/- germinal centers
      • islands of squamous cells

  • Grading

    • well differentiated
      • resembles normal squam
      • keratinizing, squamous pearls and eddies
      • mildly atypia, pale and glassy
      • often have pseudoepitheliomatous hyperplasia at periphery
    • moderately differentiated
      • less keratinizing
      • more nuclear atypia, mitosis
    • poorly differentiated
      • severe atypia, lots of mitosis, necrosis
      • minimal keratinization
      • spindled or anaplastic
      • unable to tell squamous differentiation based on morphology alone

  • Ddx

    • pseudoepitheliomatous hyperplasia (lacks atypia)
    • actinic keratosis (lacks invasion)
    • keratoacanthoma (subjective)
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