Furuncular Myiasis | Dermatopathology

Furuncular myiasis is a cutaneous infestation by dipterous fly larvae that presents as a furuncle-like papule, nodule, or abscess-like lesion, often with a central punctum or draining opening. It is classically caused by larvae such as Dermatobia hominis in Central and South America or Cordylobia anthropophaga in Africa. Histologically, the lesion may show a cavitary space containing larval structures or fragments, surrounded by dense mixed inflammation that can include neutrophilic, granulomatous, and foreign-body-type responses. Recognition of chitinous larval cuticle, spines, or other refractile arthropod structures is diagnostic. Complete removal is important, as retained larval fragments may drive persistent inflammation.

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Slide 1: Figure 1. 64-year-old woman with a subcutaneous nodule of the right areola. H&E shows a circumscribed nodular zone of striking neutrophilic and granulomatous inflammation, demarcated from adjacent fibroadipose tissue by a pseudocapsule (20×).

$Slide 2: Figure 2. H&E shows brisk necrotizing neutrophilic and granulomatous inflammation centered around a cavitary space containing refractile, ebony-black/brown corrugated spine-like structures derived from arthropod larva (100×).$

Slide 3: Figure 3. H&E shows necrotizing neutrophilic and granulomatous inflammation surrounding larval spine-like structures. The neutrophilic areas are rimmed by histiocytes, including foamy histiocytes and coalescing epithelioid granulomata (200×).

Slide 4: Figure 4. Higher-power H&E shows amorphous V-shaped larval structures measuring approximately 200 µm, consistent with chitinous spines derived from arthropod larva in cross-section (400×).

Slide 5: Figure 5. Fontana–Masson stain strongly highlights the larval spines, supporting the presence of melanin-like pigment within the chitinous cuticle, a known feature of larval exoskeletons that contributes to their structural integrity and resistance to host degradation (200×).