Approach Considerations
In most instances, a diagnosis is easily established because of the distinctive, central umbilication of the dome-shaped lesion (papule, or bump). Pseudocystic molluscum contagiosum, giant molluscum contagiosum, and molluscum contagiosum associated with other lesions may be more difficult to diagnose clinically.
If diagnosis is uncertain, lesions may be biopsied. Characteristic intracytoplasmic inclusion bodies (molluscum bodies, or Henderson-Paterson bodies) are seen on histologic examination findings.
Express the pasty core of a lesion by crushing the lesion between 2 microscope slides and staining it to reveal the particulate virions, which are present in abundance. Firm compression between the slides is required to release the virions with the stain in place. The use of crystal violet, safranin, and ammonium oxalate in 10% ethanol; the Papanicolaou test; or Wright, Giemsa, or Gram stains can reveal the virions that make up the Henderson-Paterson bodies.
Measure serum antibodies by complement fixation, tissue culture neutralization, fluorescent antibody, and gel agar diffusion techniques; however, they are not well standardized and are seldom used except in research protocols.
Polymerase chain reaction (PCR) assay can be used to detect and categorize molluscum contagiosum virus in skin lesions.
Molluscum contagiosum virus cannot be grown in tissue culture; however, Buller et al demonstrated molluscum contagiosum virus replication in an experimental system using human foreskin grafted to athymic mice. [23]
Evaluate the patient for other sexually transmitted diseases (STDs) because sexually active patients may acquire other concomitant venereal diseases, such as syphilis and gonorrhea. Always consider testing for HIV infection in patients with facial lesions.
Squash preparation
Squash preparation is microscopic examination of cellular exudate. The cellular material contained within the central umbilication may be extracted manually, flattened between 2 microscope slides, and stained. Microscopic examination of this preparation reveals the Henderson-Paterson bodies.
Histologic Findings
Lesions in molluscum contagiosum have a characteristic histopathology. [24] The prototypical hematoxylin and eosin (H&E)–stained histologic section in this disease reveals a cup-shaped indentation of the epidermis into the dermis (as seen in the images below). Downward proliferation of the rete ridges with envelopment by the connective tissue forms the crater.
This low-power view of a molluscum contagiosum lesion shows the classic cup-shaped invagination of the epidermis into dermis. The Henderson-Paterson bodies are identified readily and stained purple to red in this image.
Within the region of the indentation, the epidermis appears thickened (acanthosis), possibly measuring up to 6 times the thickness of the surrounding, uninvolved skin, and the cornified layer typically is disintegrated. The striking feature is the presence of intracytoplasmic, eosinophilic, granular inclusions within the keratinocytes of the basal, spinous, and granular layers of the epidermis.
These inclusions, the Henderson-Paterson bodies, can measure 35µm in diameter. Ultrastructural studies have shown that these bodies are membrane-bound sacs that contain numerous molluscum contagiosum virions. The viral particles increase in size as they progress up toward the granular layer, causing compression of the nucleus to the periphery of the infected keratinocytes. The surrounding dermis is relatively unremarkable. Intact lesions show little or no inflammatory change. (See the images below.)
This is a medium-power view of a molluscum contagiosum lesion. Magnification allows better demonstration of the intracytoplasmic molluscum bodies (staining purple-pink) within the keratinocytes.
Lesions of molluscum contagiosum have a characteristic histopathology. Lobules containing hyalinized molluscum bodies, also known as Henderson-Paterson bodies, are diagnostic.
This molluscum contagiosum body is an intracytoplasmic inclusion body. Notice in the image that the keratinocyte nuclei are displaced to the periphery of the cell and that the intracytoplasmic inclusions have a granular quality.
Cytoplasmic viral inclusions become progressively larger toward the epidermal surface (hematoxylin and eosin, 200X)
Viral particles have a dumbbell-shaped appearance. Courtesy of Alvin Zelickson, MD.
In nonprototypical cases of molluscum contagiosum, in which intradermal rupture of molluscum bodies occurs, an intense, inflammatory dermal infiltrate consisting of lymphocytes, histiocytes, and occasional foreign body–type, multinucleated giant cells may be observed. Rarely, metaplastic ossification may occur. Exceptionally, the inflammatory dermal infiltrate may be intense enough to simulate a cutaneous lymphoma (pseudolymphoma).
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Note the central umbilication in these classic lesions of molluscum contagiosum.
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Molluscum contagiosum. Approximately 10% of patients develop eczema around lesions. Eczema associated with molluscum lesions spontaneously subsides following removal.
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Molluscum contagiosum on the shaft of the penis. Molluscum contagiosum in the genital region of adults is most commonly acquired as a sexually transmitted disease.
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Molluscum contagiosum. Larger lesions may have several clumps of molluscum bodies rather than the more common single central umbilication. This may make them difficult to recognize as molluscum contagiosum.
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Molluscum lesions may become quite numerous in intertriginous areas. This child has autoinoculated lesions to both inner thighs.
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After trauma, or spontaneously after several months, inflammatory changes result in suppuration, crusting and eventual resolution of the lesion. This inflammatory stage does not usually represent secondary infection and seldom requires antibiotic therapy.
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Lesions of molluscum contagiosum have a characteristic histopathology. Lobules containing hyalinized molluscum bodies, also known as Henderson-Paterson bodies, are diagnostic.
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This lesion of cutaneous coccidioidomycosis could be included among the differential diagnoses of molluscum contagiosum.
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This keratoacanthoma could be included among the differential diagnoses of molluscum contagiosum.
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Molluscum contagiosum. Lesions on the upper eyelid of a 3-year-old child.
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In a patient who had preexisting molluscum contagiosum, the virus was inoculated along a line of minor skin trauma, resulting in the development of the 3 new lesions.
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Molluscum contagiosum on the right axilla.
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Presented here are the classic umbilicated papules of molluscum contagiosum lesions on the cheek of a child. Facial lesions occur frequently in children, although lesions generally are few.
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Molluscum contagiosum rarely occurs on the face in an adult unless the patient is infected with HIV. When molluscum contagiosum occurs in individuals infected with HIV, facial lesions are common and frequently numerous.
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Molluscum contagiosum lesions in individuals infected with HIV may number in the hundreds. In addition, they may become quite large and prominent.
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This low-power view of a molluscum contagiosum lesion shows the classic cup-shaped invagination of the epidermis into dermis. The Henderson-Paterson bodies are identified readily and stained purple to red in this image.
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This is a medium-power view of a molluscum contagiosum lesion. Magnification allows better demonstration of the intracytoplasmic molluscum bodies (staining purple-pink) within the keratinocytes.
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This molluscum contagiosum body is an intracytoplasmic inclusion body. Notice in the image that the keratinocyte nuclei are displaced to the periphery of the cell and that the intracytoplasmic inclusions have a granular quality.
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Multiple papules on the face of a man with HIV.
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Cytoplasmic viral inclusions become progressively larger toward the epidermal surface (hematoxylin and eosin, 200X)
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Low-power histopathologic examination reveals an overall cup-shaped appearance.
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Viral particles have a dumbbell-shaped appearance. Courtesy of Alvin Zelickson, MD.
