NECROTIC LESION OF VIRAL ORIGIN (HERPES; HERPES ZOSTER CLINICALLY)
Herpes simplex and herpes zoster cause similar nuclear and cytologic changes. Loss of nuclear chromatin, margination of chromatin along an irregularly thickened nuclear membrane, 'steel gray' nuclear alteration, and, less commonly, eosinophilic nuclear inclusions are the nuclear features. Multinucleated cells having these  changes are emphasized in textbooks, but the diagnosis can be made based upon the nuclear morphology of mononuclear keratinocytes. Keratinocyte enlargement, ballooning degeneration and/or reticular degeneration of the keratinocytes are/is characteristic. The host response is quite variable in intensity from case to case and may not be apparent in late, necrotic lesions. Intraepidermal vesiculation is a common feature. Necrosis of pilosebaceous units is not common, but when present, may be striking, and there are rare cases where the manifestations are restricted to pilosebaceous units. A search for diagnostic nuclear features near the edge of the intraepidermal component can be helpful in advanced, necrotic lesions.

A biopsy from the elbow area of a 70 year old male. After a pathologic diagnosis of viral dermatitis was made, the clinical evaluation was that this is herpes zoster. The patient has no overt evidence of immune deficiency.
Scan power view. Superficial necrosis and vesicle formation are extensive.
Composite low power view of above that is centered on the necrotic pilosebaceous unit. Note the prominent swelling and eosinophilic change (ballooning degeneration) of the keratinocytes. Acantholysis is common when there is this much ballooning degeneration.
A very high power view of the epidermis from an area near the edge of the lesion. Note the irregular thickening of the nuclear membrane associated with 'steel gray' alteration of the nucleus of the cell in the center of the picture.
A high power view of another field in the epidermis. Two multinucleated keratinocytes are in the picture, and characteristic nuclear changes are seen in the cell in the center of the picture.

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