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Viral infections, helminths, and arthropods


Viral infections

Warts

Verruca vulgaris

Key Features

  • Exophytic

  • Papillomatosis

  • Compact eosinophilic hyperkeratosis

  • Coarse hypergranulosis in dells

  • Vertical tiers of round parakeratosis common above peaks

  • Blood and serum common above peaks

  • Koilocytes variable

The biopsy will demonstrate a compact stratum corneum, coarse hypergranulosis, and papillomatosis. The papillomatosis often curves inward. Vascular ectasia is common. Koilocytes (vacuolated cells with hyperchromatic shriveled nuclei) may be present. Red cytoplasmic inclusions may sometimes be present.

Fig. 19.1, Verruca vulgaris

Myrmecia

Key Features

  • Deep palmoplantar wart with anthill-like appearance clinically

  • Endophytic

  • Coarse red cytoplasmic inclusions

Myrmecia are associated with human papillomavirus 1 (HPV-1).

Fig. 19.2, Myrmecia

Verruca plana (flat wart)

Key Features

  • Coarse basket-weave hyperkeratosis

  • Hypergranulosis common

  • “Bird's eye” cells (like koilocytes but lack shriveled nuclei)

Fig. 19.3, (A and B) Verruca plana. (C) Verruca plana with changes characteristic of epidermodysplasia verruciformis

Epidermodysplasia verruciformis (EDV)

Key Feature

  • Widespread, flat warts with foamy blue cytoplasm

Condyloma acuminatum

Key Features

  • Benign acanthoma on genital skin

  • Areas of compact stratum corneum, round parakeratosis, and coarse hypergranulosis generally present

  • Vacuolated keratinocytes, typically with large gray nuclei

  • True koilocytes rare

Condylomata acuminata commonly have horn cysts and resemble seborrheic keratoses. The two are differentiated by areas of compact stratum corneum, round parakeratosis, coarse hypergranulosis, and vacuolated keratinocytes with large gray nuclei. In situ hybridization can identify the HPV type.

Fig. 19.4, (A and B) Condyloma accuminatum. (C) Condyloma acuminatum in situ hybridization for low-risk HPV (types 6 and 11)

Bowenoid papulosis

Key Features

  • HPV-16 most commonly

  • Atypia

Bowenoid papulosis presents as discrete pink, brown, or gray lesions in the genitalia. They are typically sessile rather than papillomatous or cauliflower-like. The histologic spectrum ranges from that of a condyloma with buckshot scatter of atypical cells to full-thickness atypia, indistinguishable from Bowen disease.

Fig. 19.5, Bowenoid papulosis

Heck disease

Key Features

  • Focal oral hyperplasia

  • Hyperkeratosis with round parakeratosis

  • Epithelial pallor

  • HPV-13 and -32

Pearl

Type of wart HPV type
Common 1, 2, 4
Flat (verruca plana) 3, 5
Plantar 1 (myrmecia), 2, 4 (mosaic)
Epidermodysplasia verruciformis 5, 8, and many others
Buschke–Löwenstein tumor 6, 11
Butcher's 7 and others
Laryngeal papillomas 6, 11
Genital dysplasia 16, 18, 31, 33, 35, and others
Heck focal oral hyperplasia 13, 32
Subungual squamous cell carcinoma 16

Fig. 19.6, Heck disease

Verrucous cyst (cystic papilloma)

Key Features

  • Cyst with wartlike lining

Verrucous cysts may arise as a result of papillomavirus infection of a hair follicle. On plantar surfaces, they may arise from eccrine ducts, and the lining is more likely to resemble myrmecia.

Fig. 19.7, Verrucous cyst

Herpetic infections

Herpes simplex

Key Features

  • Ballooning degeneration of keratinocytes

  • Multinucleated keratinocytes with nuclear molding

  • Herpetic cytopathic effect (basophilic eggshell of chromatin at the periphery of the nucleus)

  • Mild features of leukocytoclastic vasculitis may be present

Fig. 19.8, Herpes simplex

Herpes zoster (varicella-zoster virus: VZV)

Key Features

  • Ballooning degeneration of keratinocytes

  • Multinucleated keratinocytes with nuclear molding

  • Herpetic cytopathic effect (basophilic eggshell of chromatin at the periphery of the nucleus)

  • Dramatic leukocytoclastic vasculitis typical

Fig. 19.9, Herpes zoster (shingles)

Fig. 19.10, Varicella (chicken pox)

Fig. 19.11, Verrucous zoster

Chicken pox (VZV)

Key Features

  • Ballooning degeneration of keratinocytes

  • Multinucleated keratinocytes with nuclear molding

  • Herpetic cytopathic effect (basophilic eggshell of chromatin at the periphery of the nucleus)

  • Mild features of leukocytoclastic vasculitis may be present

Verrucous VZV infection

Key Features

  • Compact hyperkeratosis

  • Variable papillomatosis

  • Follicular herpetic cytopathic effect

Multinucleated giant cells with basophilic nuclear rims and nuclear molding are noted within follicular epithelium. This pattern is typically seen in immunosuppressed patients, especially in the setting of human immunodeficiency virus (HIV) infection.

Cytomegalovirus

Key Features

  • Large endothelial cells with owl's-eye nuclei

  • Cytoplasm may be ample or scant

In HIV patients, cytomegalovirus probably does not cause ulcers, but reactivates within ulcers. Viral cytopathic changes may be found in ulcers of various causes. This alerts the clinician to look for evidence of cytomegalovirus retinal involvement.

Fig. 19.12, Oral hairy leukoplakia

Oral hairy leukoplakia

Key Features

  • HIV-associated Epstein–Barr virus (EBV) infection

  • Nuclear stippling characteristic

  • In situ hybridization (Epstein–Barr encoding region [EBER]) is helpful for confirmation

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