Large cell acanthoma usually presents as a well demarcated solitary plaque or scaly, lightly pigmented patch on sun exposed skin. 

HPV type 6 is considered an important cofactor in the pathogenesis of large-cell acanthomas.

Site:  Usually  located on the face, or on the limbs and trunk.

Histopathological examination reveals sharp demarcation of the lesion from the normal epidermis.

       Image Link1  ;  Image Link2

The thickened  epidermis consists of enlarged keratinocytes, twice the normal size.

Other features include basket weave orthokeratosis, prominent hypergranulosis, and  hyperpigmentation of basal layer.

 In the dermis telangiectasia, solar elastosis  and chronic inflammation may be present.

[Large-cell acanthoma is a distinctive condition.Am J Dermatopathol. 1992 Apr;14(2):140-7; discussion 148.]

Differential diagnosis includes solar lentigo and solar keratosis. 

(Note: In solar keratosis there is parakeratosis,  in large cell acanthoma there is orthokeratosis)

                            IMAGE  LINK (Dr Weems)