Calcium oxalate crystals in benign cyst fluid from the breast. A case report.

BACKGROUND: Two types of calcification have been observed in breast lesions. The more common is composed mostly of calcium phosphate and is detected in routine histologic tissue sections of frequently malignant lesions. The rare type is calcium oxalate and is found exclusively in benign cysts. CASE: In a 47-year-old female, strongly birefringent polyhedral crystals of calcium oxalate were detected in benign breast cyst fluid. CONCLUSION: Calcium oxalate is not clearly visible on routine histologic sections, and examination of the cytologic specimens under polarized light reveals them. Awareness of this potential pitfall might lead to conservative management.