Aims: Complex or composite adnexal tumours of the skin (CATS) are unusual neoplasms composed of two or more histopathologically distinct subtypes of appendageal neoplasms coexisting in a single cutaneous lesion. The authors report three examples of CATS, review literature and discuss their probable histogenesis.
Methods and results: Of the three tumours described, one tumour showed a mixture of a proliferating pilar tumour and syringocystadenoma papilliferum, the second lesion was composed of a proliferating pilar tumour and tubulopapillary hidradenoma and the third tumour exhibited a syringocystadenoma papilliferum and tubulopapillary hidradenoma in combination.
Conclusions: CATS are rare tumours. The authors reported three unique cases in addition to the 10 other reported cases. These three cases further strengthen the hypothesis of a 'folliculosebaceous apocrine' unit as the most likely point of origin of CATS.