GPR: 2020 - Week 43

From MGH Learn Pathology

Clinical history

A 44 year-old male with a single, quarter-sized, non-pruritic, non-scaly brown macule with a sharp, dark border on the palmar surface of his left hand


Registered users must be logged in to access the interactive quiz.


Hortaea werneckii
  • Superficial pheohyphomycosis - tinea nigra palmaris
  • Asymptomatic/pruritic, non-scaly, mottled macule
  • Dematiaceous = melanin
  • Macule (and culture) darkens to brown-black
  • Olive/greenish black mucoid colonies w/aerial mycelium



Trichophyton rubrum

  • Tinea corporis, annular, scaly lesions with central clearing, slightly elevated edge
  • Also tinea pedis and unguium
  • Cultures mature within 14 days, produce an array of pigments
  • Surface granular to fluffy, white to buff
  • Reverse deep red, purple, brown, yellow-orange, or colorless



Malassezia furfur

  • Pityrosporium orbiculare/ovale
  • Pityriasis versicolor
  • Stratum corneum
  • Scaly hypo/hyperpigmented trunk lesions
  • Saphrophitic, lipophilic yeast (culture w/LCFA)
  • Colonies cream/yellow, smooth/lightly wrinkled, glistening/dull, entire or lobate margin

  • Patel, Seema, Meixner, Jeffrey A, Smith, Michael B, & Mcginnis, Michael R. (2017). Superficial Mycoses and Dermatophytes. In Tropical Dermatology (Second ed., pp. 189-201).
  • Connor, D.H., et al., 1997. Pathology of Infectious Diseases. Appleton & Lange, Stamford, CT.
  • Hayden, Randall T ; Walsh, Thomas J ; Larone, Davise H. (2018). Identification of Fungi in Culture. In Larone’s Medically Important Fungi (pp. 73-331). Washington, DC, USA: ASM Press.

This week's Gross Pathology Roundup was presented by William Rothwell MD on 2020-10-19.