Filaggrin immunoreactive composite keratohyalin granules specific to acrosyringia and related tumours.

The luminal cell layer of acrosyringia contains heterogeneous globular keratohyalin granules, some of which contain basophilic and eosinophilic components. Using immunoelectron microscopy we found that the majority of the granules, which are basophilic, are strongly reactive to an anti-filaggrin antibody, while the minority, which are eosinophilic, are not. Similar heterogeneous keratohyalin granules were observed in syringomas and in an eccrine syringofibroadenoma. Since such granules are not normally observed in other human cutaneous epithelia, it is suggested that these composite keratohyalin granules with partial filaggrin immunoreactivity might serve as a useful marker for acrosyringial differentiation in both normal and pathological material.