Author: PathologyMCQ Editorial Team
Category: Dermatopathology / Infectious Pathology
Last Updated: October 2026
Read Time: 12 minutes
Difficulty: Moderate (MD/DNB, FRCPath, NEET-SS)

At a glance

• Molluscum contagiosum: poxvirus; umbilicated papules on non-acral skin; lobulated cup-shaped lesion packed with uniform intracytoplasmic molluscum (Henderson–Patterson) bodies.
• Myrmecia wart: HPV 1; painful deep palmoplantar wart; endophytic “ant-hill” lesion with coarse, irregular eosinophilic inclusions of varying size.
• Two-step rule: architecture (crater vs inward-growing papilloma), then inclusions (uniform vs variable).
• In this post: zoomable virtual slides of molluscum, myrmecia and a herpes simplex mimic, a mimics table, and 10 interactive MCQs including 6 slide-based questions.

Who this is for: NEET-SS and INI-SS (DM Histopathology / Oncopathology) aspirants, FRCPath Part 1 and Part 2 histopathology candidates, MD/DNB pathology residents preparing for theory, practical and viva exams, and anyone doing APCP board preparation or general pathology board preparation. Want just the slides and notes? Open the molluscum vs myrmecia virtual slide guide with free PDF.

What is molluscum contagiosum?

Molluscum contagiosum is a common viral infection of the epidermis caused by molluscum contagiosum virus (MCV), a large DNA poxvirus that replicates in the cytoplasm of keratinocytes. The viral “factories” build up as large intracytoplasmic inclusions within a cup-shaped epidermal lesion.

• Virus: MCV (Poxviridae); MCV-1 causes most infections, MCV-2 is relatively more common in adults and in HIV.
• Spread: direct skin contact, autoinoculation (scratching), fomites, and sexual contact in adults.
• Who: children, sexually active adults (genital lesions) and immunosuppressed patients, in whom lesions can be numerous, large and facial.

What is a myrmecia wart?

Myrmecia (from the Greek for “ant-hill”) is a deep, inward-growing palmoplantar wart caused by human papillomavirus type 1 (HPV 1). It produces a distinctive cytopathic effect: large, coarse eosinophilic inclusions that differ from the koilocytes of common warts.

• Virus: HPV 1 (a low-risk, cutaneous type).
• Site: soles (especially pressure points) and palms; often solitary.
• Symptoms: painful on pressure because it grows deep into the dermis.

Clinical picture: molluscum

• Small, firm, smooth, pearly papules with central umbilication; the umbilication is the histological crater.
• Trunk, flexures, thighs and genital skin; usually spares palms and soles.
• Inflamed or scratched lesions can become red and crusted and may mimic folliculitis.

Clinical picture: myrmecia

• Dome-shaped, deep, often solitary wart on the sole or palm, painful on pressure.
• Rough keratotic surface; paring may show black dots (thrombosed capillaries).
• No central umbilication, unlike molluscum.

Histopathology of molluscum contagiosum

Architecture: a lobulated crater

• Pear-shaped lobules of acanthotic epidermis grow down into the dermis (endophytic), separated by thin dermal septa.
• The lobules converge on a central crater that opens onto the surface and is filled with shed molluscum bodies and keratin.
• Lesions may sit within or replace hair follicles.

Inclusions: uniform molluscum (Henderson–Patterson) bodies

• Basal cells look normal; small eosinophilic intracytoplasmic inclusions appear in the lower spinous layer.
• As cells mature the bodies enlarge to fill the cell, compressing the nucleus into a thin crescent at the edge.
• In the granular and horny layers they become paler or basophilic and are shed into the crater.
• They are strikingly uniform in size and shape, the key difference from HPV inclusions.
• Inflamed molluscum: rupture releases bodies into the dermis, causing a heavy mixed or granulomatous infiltrate that can hide the diagnosis; look hard for residual bodies.

Histopathology of myrmecia wart

See it on a real case: open the Myrmecia wart tab in the virtual slide viewer and zoom into the granular layer.

Architecture: an inward-growing “ant-hill”

• Endophytic papillomatous proliferation that pushes deep into the dermis, with a thick hyperkeratotic surface.
• Elongated rete ridges curve inwards towards the centre, giving a dome or cup shape.
• Columns of parakeratosis over dermal papillae, sometimes with haemorrhage (the clinical black dots).

Inclusions: coarse, irregular and variable

• Large, deeply eosinophilic keratohyalin-like intracytoplasmic inclusions that clump and coalesce as cells move upwards.
• Small eosinophilic intranuclear inclusions and vacuolated cells with pyknotic nuclei.
• Inclusions vary in size and shape, unlike uniform molluscum bodies.

Side-by-side comparison

Feature	Molluscum contagiosum	Myrmecia wart
Virus	Poxvirus (MCV)	HPV 1
Site	Non-acral skin: trunk, flexures, genital, face	Palms and soles
Clinical	Pearly umbilicated papules, often multiple	Deep, painful, often solitary wart
Architecture	Lobulated endophytic lesion with a central crater	Endophytic papilloma with inward-curving rete ridges
Inclusions	Uniform, smooth, intracytoplasmic; eosinophilic below, basophilic near surface	Coarse, irregular, coalescing eosinophilic cytoplasmic plus small intranuclear inclusions
Nucleus	Compressed into a peripheral crescent	Pyknotic, often in a vacuolated cell
Diagnostic hallmark	Crater + uniform bodies	Ant-hill architecture + variable inclusions

Histological mimics and how to tell them apart

Mimic	Shared feature	Distinguishing clue
Verruca vulgaris (HPV 2, 4, 27, 57)	Papillomatous wart	Exophytic, church-spire hyperkeratosis, koilocytes, coarse keratohyalin granules; no large inclusions
HPV 4 plantar wart	Plantar site	Vacuolated cells without the large coarse inclusions of HPV 1
Keratoacanthoma	Crateriform, cup-shaped lesion	Keratin-filled crater, glassy eosinophilic keratinocytes, lips of epidermis; no viral inclusions
Herpes simplex / varicella-zoster	Viral cytopathic effect	Intraepidermal vesicles, ballooning, multinucleation, moulding, margination and Cowdry A intranuclear inclusions
Orf / milker’s nodule (parapoxvirus)	Eosinophilic intracytoplasmic poxvirus inclusions	Finger after animal contact, ballooning, epidermal necrosis, oedematous vascular dermis
Condyloma acuminatum (HPV 6, 11)	Papillomatous HPV lesion	Anogenital site, broad papillae, koilocytes; no crater or molluscum bodies
Cryptococcosis or histoplasmosis in HIV	Clinically molluscum-like papules	Yeasts in the dermis on PAS, GMS or mucicarmine; no epidermal inclusions

Clinicopathological correlation

Clue	Points to
Painful palmar or plantar wart	Myrmecia (HPV 1)
Pearly umbilicated papules on non-acral skin	Molluscum contagiosum
Many large facial lesions in an adult	Molluscum with immunosuppression (check HIV); exclude cryptococcosis
Uniform intracytoplasmic inclusions on biopsy	Poxvirus (molluscum)
Coarse, variable inclusions in palmoplantar skin	HPV 1 cytopathic effect
Crateriform lesion without inclusions in sun-damaged skin	Keratoacanthoma

More practice: molluscum and wart quiz

Exam pearls and key takeaway

• Uniform intracytoplasmic bodies in a lobulated crater = molluscum contagiosum.
• Painful palmoplantar wart with ant-hill architecture and coarse, variable eosinophilic inclusions = myrmecia (HPV 1).
• Intranuclear inclusions with multinucleation and moulding = herpesvirus, not molluscum.
• Crater with a keratin plug but no inclusions = think keratoacanthoma.
• Key takeaway: read the architecture first (crater vs inward papilloma), then the inclusions (uniform vs variable, cytoplasmic vs nuclear), and always correlate with the site.

Video summary