Crystallizing galactocele. A case report

Galactoceles are benign cystic lesions that generally occur during pregnancy and postpartum lactation. Fine needle aspiration (FNA) yields milky fluid that is often both diagnostic and therapeutic. Cytologically, aspirates are generally noted to contain occasional foam cells and benign epithelium displaying lactational change with an abundant background of lipid micelles and proteinaceous material.

A 23-year-old, black female presented with a 1.0-cm, discrete, nontender nodule involving the upper middle area of the left breast. FNA showed crystals of varying size and shape, best viewed with Diff-Quik and demonstrating metachromasia, polarization and birefringence. They were also positive with periodic acid-Schiff stain and both alizarin red S and von Kossa stain for calcium. Scanning electron microscopy revealed angulated, well-defined geometric crystals often with scalloped edges and smooth surfaces. The internal structure of the crystals consisted of electron-lucent material without periodicity or lattice formation, as observed by transmission electron microscopy and x-ray diffraction. Electron probe microanalysis identified small quantities of calcium, chlorine, potassium and sulphur within the crystals.

We think that in this case the crystals represented precipitation of inspissated lactational secretions. There are several possible mechanisms of precipitation. The differential diagnosis includes other breast lesions with acellular amorphous components that may be confused with crystallizing galactocele in FNA biopsy specimens.