Figure 2

Histopathology of cutaneous pythiosis in a harbour porpoise. Sections of skin stained with Haematoxylin & Eosin (H&E; A, C) or Grocott silver stain (B, D). Original magnifications: ×100 (A, B) or ×400 (C, D). A The Pythium flevoense organisms predominantly invaded the superficial layer of squamous non-keratinised epithelium of the skin (darker stained top layer) and were poorly visible in the H&E-stained tissue as well-delimited round to oval empty spaces (arrow) compared to B the high visibility in the Grocott silver stain showing the abundant presence of black-stained organisms. C Close-up of a rare H&E-stained hypha (arrow) amidst many non-stained hyphae (arrow heads) compared to the Grocott silver-stained serial section D showing many irregular angular and infrequent septate (arrow heads) hyphae with frequent bulbous swellings (arrow).