Nerve-like myoid differentiation in sclerosing adenosis of breast. A diagnostic pitfall.

A surgically excised lesion from the breast of a 33 year old woman showed apart from cystic disease sclerosing adenosis with distinct myoid differentiation. The myoid bundles were wrapped around original ductules producing a misleading picture which simulated tangentially cut nerves, infiltrated by tumour glands. Immunohistochemically, actin positivity and S-100 protein negativity confirmed the nature of the lesion as sclerosing adenosis.