Path Quiz Case-67:-  Diagnosis:

       Path Quiz Online:CASE HISTORY AND IMAGE:

Dermatopathology Case No 25 (Images)

Clear cell acanthoma (pale cell acanthoma) is a discrete idiopathic psoriasiform lesion of large pale staining, non-keratinizing, glycogenated, monomorphous keratinocytes associated with neutrophils. The lesion is separated from the adjacent epidermis.

Clinical presentation:  Presents as a firm brown-red dome shaped nodule or papule. The lesion is usually between 5 to 10 mm or more in diameter. It is usually solitary but can be multiple. Clinical bleeding is rare. The surface of the lesion may be smooth to bosellated and crusted.

Age:  Middle aged and elderly individuals. Some cases have been reported in younger patients.

Site: Commonly located on the lower limbs. These may also be found on the trunk and face.

Microscopic features: Image Link1 ; Image Link2 ; Image Link3 ; Image Link4 ; Image Link5

Well-demarcated and symmetric lesion elevated in comparison to surrounding skin. The base of the lesion situated below the rete- ridges of the normal epidermis.

A sharp line can be drawn between the lesional cells and normal epidermis.

There is psoriasiform hyperplasia of the rete ridges with broad base.

The keratinocytes have pale-staining cytoplasm. A PAS stain with and without diastase confirm the presence of abundant glycogen in the cells.

There is usually no cellular atypia.

Other epidermal changes include mild spongiosis and exocytosis of neutrophils forming small intraepidermal microabscesses

The epidermal surface shows parakeratotic scales.

Melanocytes within the lesions are variable in number.  A pigmented variant has been reported.

Papillary dermis is edematous and dermal capillaries are prominent.

An inflammatory infiltrate composed of lymphocytes ,plasma cells and rarely eosinophils are present.

Immunohistochemistry:  The cells contain cytokeratin and involucrin but not carcinoembryonic antigen.

Differential diagnosis:Eccrine poroma ; Trichilemmoma ; Psoriasis;  Clonal type- Seborrheic keratosis ;  Verruca vulgaris .