Porokeratosis

Early

Superficial perivascular infiltrate of lymphocytes
Lichenoid infiltrate of lymphocytes in foci beneath columns of parakeratosis positioned at either end of the lesion
Columns of parakeratosis bending inward at the periphery of the lesion; hypogranulosis immediately beneath each column, and dyskeratotic cells and vacuolated cells in the spinous zone

Fully developed

Lichenoid infiltrates of lymphocytes across the front of the lesion, i.e., between poles formed by columns of parakeratosis
Wiry bundles of collagen in haphazard array accompanying lichenoid infiltrates of lymphocytes
Telangiectases and melanophages present often in the zone of altered bundles of collagen
Thinned and compactly orthokeratotic epidermis between columns of parakeratosis at the periphery of the lesion

Late

All the findings in a fully developed lesion, except inflammatory cells, which are absent

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