Reappraisal of breast hamartomas. A morphological study of 41 cases.

Mammary hamartomas are breast disorders currently underestimated and not well recognized. Forty-one hamartomas diagnosed among 5,834 breast biopsies, histologically examined during the last 7 years, are reported. Hamartomas accounted for 1.2% of benign lesions and 4.8% of benign breast tumors. Clinically, hamartomas were revealed by breast palpable lump, usually painless. Typically, but inconsistently, mammography showed sharply circumscribed density, separated from adjacent normal breast by a thin radiolucent zone. Macroscopically, hamartomas were slightly larger and softer than common adenofibromas, were well limited, whitish, pinkish and fleshy, with yellow islands of fat tissue. Histologically, hamartomas exhibited pushing borders with a pseudoencapsulation, and consisted of a combination of variable amount of stromal and epithelial components. Stromal components mainly consisted in a prominent fibrohyalin feature usually associated to small islands of adipose tissue and edematous changes. Epithelial structures showed variable features of benign breast disease. The overall architecture was lobulated but not nodular. The histological diagnosis was mainly a diagnosis of exclusion and hamartomas diagnosis relies on clinical, radiological and pathological criteria. Hamartomas result more from breast dysgenesis than from tumorous process.