Apocrine acrosyringeal keratosis in association with syringocystoadenoma papilliferum

We report the clinical and histopathological features of a keratosis that developed in association with syringocystadenoma papilliferum. This tumour shows a pinkish, pedunculated, spherical nodule with a cerebriform surface and visible keratinous plugs. In addition to the typical features of syringocystadenoma papilliferum, the tumour shows many hyperkeratotic columns surrounded by acanthotic epidermis with the characteristics of trichilemmal keratinization and keratohyalin granules. This keratosis seems to be derived from the middle to lower portion of the apocrine acrosyringium, based on the distribution of keratohyalin granules and the direct connection with the apocrine acrosyringium in an early lesion. Accordingly, we propose to identify this rare keratosis as apocrine acrosyringeal keratosis.