[Cutaneous apocrine mixed tumor with follicular differentiation]. / Apokriner kutaner Mischtumor mit follikulärer Differenzierung.

An 85-year-old man presented with a firm, papillomatous nodule on the upper lip, which had been growing slowly for 30 years. Histopathologic examination revealed an apocrine mixed tumour with follicular differentiation. Mixed tumours of the skin are rare benign neoplasms, which are composed of different tissue components, e.g. epithelial and glandular elements and myxoid or chondroid components. Mixed tumours with apocrine differentiation can be discriminated from mixed tumours with eccrine differentiation. Criteria for apocrine differentiation are: decapitation secretion, elongated gland-like and duct-like structures lined with two rows of epithelial cells and branching of tubular structures. Follicular structures are another clue to the apocrine differentiation of neoplasms. The designation mixed tumour is preferable to chondroid syringoma, because most mixed tumours show apocrine differentiation. The differential diagnosis of apocrine mixed tumour includes fibroadenoma, hidradenoma, mucinous adenocarcinoma, adenoid cystic carcinoma, and rare soft tissue tumours like the myxoid chondrosarcoma.