This video discusses the dermatopathological differentiation between two common lookalike skin lesions: Molluscum Contagiosum and Myrmecia Wart (a type of plantar wart). The speaker highlights key diagnostic features using microscopic images. Molluscum Contagiosum typically presents as umbilicated papules, showing a cup-shaped epidermal invagination containing characteristic uniform, homogeneous pink-to-purple viral inclusions known as Henderson-Patterson bodies. These lesions are generally found on non-acral skin. Myrmecia Warts, conversely, are large, painful plantar warts found almost exclusively on acral skin (palms/soles). Microscopically, they exhibit a cup-shaped depression with multiple finger-like papillary projections (pili) and contain inclusion-like granules that are distinctly variable in size, shape, and angulation, unlike the uniform bodies of molluscum. The clinical location and the specific morphology of the intracellular inclusions are presented as the most crucial distinguishing factors for accurate diagnosis.
Differentiating Molluscum Contagiosum and Myrmecia Wart: A Dermatopathology Guide
0:00 Introduction: The video focuses on differentiating Molluscum Contagiosum from Myrmecia Wart, a type of plantar wart, often confused in dermatopathology.
0:31 Molluscum Contagiosum - Clinical Appearance: Presents as umbilicated papules (with a central divot) on the skin, commonly in children but also adults. It's caused by a poxvirus, is benign, and often resolves on its own.
1:13 Molluscum Contagiosum - Microscopic Features (Henderson-Patterson Bodies): Characterized by a cup-shaped epidermal invagination. Key diagnostic features are large, homogeneous pink-to-purple viral globules called Henderson-Patterson bodies (or molluscum bodies), which originate in keratinocytes and accumulate in the central cystic space.
Key Takeaway: These bodies are very uniform in size and shape, appearing smudgy and glassy pink, distinguishing them from keratohyalin granules.
2:57 Molluscum Contagiosum - Varied Histologic Presentation: Lesions can be sectioned off-center, appearing as a papule with a cyst. Ruptured molluscum can induce a significant inflammatory response, sometimes mimicking an abscess or even squamous cell carcinoma, requiring careful examination for Henderson-Patterson bodies. The epithelium often shows distinct, pushing-out lobules.
5:02 Myrmecia Wart - Clinical Appearance & Location: Typically a very large, deep, painful plantar wart (verruca plantaris) found on the sole of the foot or other acral skin (palms/fingers/toes). Caused by HPV type 1.
5:50 Myrmecia Wart - Microscopic Architecture: Characterized by a large, cup-shaped depression that extends deep into the dermis, filled with multiple finger-like papillary projections (pili) of squamous epithelium. Features include dilated vessels, parakeratosis over the pilli tips, and often hemorrhage.
6:30 Myrmecia Wart - Microscopic Features (Granules): Contains inclusion-like granules that can be magenta-pink, but unlike molluscum bodies, they are highly variable in size and shape (irregular, chunky, angulated), not uniform. The name "Myrmecia" refers to an ant genus, as the granules can resemble ants swarming on an ant hill.
Clinical Location: Molluscum is almost never on palms/soles; Myrmecia is almost exclusively on acral skin.
Architecture: Molluscum shows a simple cup-shaped depression, often with a central cystic space. Myrmecia has a cup-shaped depression with prominent, multiple papillary projections (pilli).
Inclusions: Molluscum has uniform, smudgy Henderson-Patterson bodies. Myrmecia has irregular, variable-sized, chunky, and angulated pink/purple granules.
9:34 Diagnostic Test Cases: The video presents several examples (at 9:34, 11:15, 12:01, 13:09, 14:26, 15:52, 17:08, 19:04) demonstrating how to apply these differentiating features, including cases with atypical presentations like ruptured molluscum or small biopsies of myrmecia wart.
20:09 Conclusion: Both lesions are benign and become straightforward to diagnose once the specific microscopic and clinical differences are understood.