Irritated seborrheic keratosis with coarse keratohyalin granules

The viral etiology of certain types of seborrheic keratosis (SK) has been a controversial subject in literature, with different molecular results. On the contrary, to the molecular approach, some have suggested that certain types of SK are indeed warts, due to their morphologic features. We decided to investigate the presence of coarse keratohyalin granules in cases of irritated SK.

We examined the last 60 cases with such a diagnosis in our Service of Anatomic Pathology and found these granules in eight cases (7.5%). The granules were evidenced in squamous eddies in four cases, while they were seen in foci of hypergranulosis from the top part of the epidermis in five cases. These granules were evidenced in a few foci in three cases while they were seen in multiple foci in five cases. In these eight cases, we also looked for other morphologic signs suggesting a viral origin, such as papilated, exo-endophytic configuration, parakeratosis at the tips of digitations, dilated vessels in the papillae and koilocytes. While six cases presented at least any of these other features, in two of the eight cases (25%), the only clue suggesting a viral origin was the evidence of the thick granules of keratohyalin.

We discuss the meaning of such a finding as described in literature, and conclude that it should be a specific feature to look out for, in cases of irritated SK, in order to exclude a diagnosis of verruca vulgaris.