Fine-needle aspiration of apocrine hidrocystoma--a potential mimic of papillary neoplasms metastasizing to the skin.

We report the cytologic features of a histologically confirmed apocrine hidrocystoma as seen in fine-needle aspirates. The main cytologic features were the presence of sparse pseudopapillae with mild to moderate atypia in a background of an amorphous navy blue material reminiscent of that seen in aspirates of colloid nodules of the thyroid gland. The pseudopapillae were mistaken for malignant metastatic deposits. It is suggested that the presence of pseudopapillae in aspirates obtained from cutaneous nodules might be a clue for a tentative diagnosis of benign tumors of epidermal adnexae, with the proviso that a primary malignant tumor be ruled out first.