#dermpathJC January 2020:

Thursday, January 23rd, 9 pm EST

Article discussed: Invisible dermatosis, disgnostic discrepancy between the general pathologist and dermatopathologist

Authors: Ahmed Alhumidi, Najd Alshamlan, Mona Alfaraidi, Khaled Mohajer

Temporary open access courtesy of Journal of Cutaneous Pathology at: : https://onlinelibrary.wiley.com/doi/pdf/10.1111/cup.13554

Summary prepared by: Cacey Peters, M.D. (@caceypeters)

Journal Club Summary:

• Invisible dermatoses are those that have subtle histologic features but have been biopsied because of obvious clinical lesions.
• Often, a diagnosis of no significant pathological changes or nonspecific findings will be made by a general pathologist.
• 81 total cases were reviewed over the past 15 years where general pathologists, with experience ranging from 5-20 years, made one of the following diagnoses:
  • No specific diagnosis
  • No significant pathologic changes
  • Minimal pathologic changes
• These cases were reviewed retrospectively and blindly by a dermatopathologist trained at a reputable center in the United States with 5 years of experience in dermatopathology.
• Out of 81 total cases, 43 (53%) were found to have a specific diagnosis while the remaining 38 (46.9%) remained non-specific. Of the nonspecific cases, 15 (39.47%) were due to inadequacy of the specimen.
• This study aims to highlight the diagnostic challenges of invisible dermatosis, the importance of clinicopathologic correlation, biopsy adequacy/preparation, and histochemistry.
• Conditions that are likely to receive a nonspecific diagnosis by a general pathologist include:
  • Becker’s melanosis
    • Clinically pigmented patches
    • Shoulder, back, or chest
    • Histologically – regular elongation of the rete ridges with basal hyperpigmentation
  • Spongiotic dermatitis – intercellular epidermal edema
    • Eczema
    • Id reaction
    • Pityriasis rosea
    • Pityriasis alba (children, hypopigmented patches that can mimic mycosis fungoides)
    • Many others
  • Pigmented purpuric dermatosis (extravasated red blood cells and hemosiderin-laden macrophages)
    • Progressive pigmentary dermatosis of Schamberg (subtle deposits and scant inflammation)
    • Purpura annularis telangiectodes of Majocchi
    • Eczematoid-like purpura of Doucas and Kapentanakis
    • Pigmented purpuric dermatitis of Gougerot and Blum
  • Increased dermal mucin (often subtle, can use Alcian blue and colloidal iron stains)
    • Generalized myxedema
    • Pretibial myxedema
    • Lichen myxedematosus
    • Papular mucinosis
    • Reticular erythematous mucinosis
    • Self-healing juvenile cutaneous mucinosis
    • Scleroderma
  • Pityriasis/tinea versicolor (caused by Malassezia furfur)
  • Acute generalized exanthematous pustulosis (AGEP)
  • Mycosis fungoides (cutaneous T-cell lymphoma)
  • Urticaria (if resolves within 24 hours; if chronic, suspect urticarial vasculitis)
  • Primary cutaneous amyloidosis (HMWCK+)
  • Vitiligo
  • Telangiectasia macularis eruptive perstans (TMEP; mastocytosis, highlighted by Giemsa, toluidine blue, and CD117)

This pie chart illustrates the types of diagnoses were rendered by dermatopathologists when they reviewed pathology slides without significant pathology or no diagnosis report.

Memorable Tweets:

Differential diagnosis of invisible dermatoses. A mnemonic by @SGottesmanMD.

Thank you so much for attending #DermpathJC and for reading this summary.

We are always here for you and your dermatopathology learning,

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