Apocrine hidrocystoma. A, Low-power photomicrograph shows a partially collapsed cyst that is lined by a double layer of epithelium (ie, an inner, low cuboidal layer and an outer, flattened myoepithelial layer). The lumen appears empty as the clear liquid contents are not visible on routine histologic examination. B, High magnification shows apocrine differentiation with cytoplasmic projections (snouts) on the inner surface (arrowheads) that are typical of decapitation secretion.