Cytological features of breast peri-implant papillary synovial metaplasia.

Synovial metaplasia is a peculiar form of metaplasia seen in the inner lining of the fibrous capsule that surrounds breast implants. Since the description of breast-implant associated anaplastic large cell lymphoma it is increasingly common to receive periprosthetic breast fluid collections for pathologic analysis. We describe a case of breast-implant papillary synovial metaplasia that showed remarkable cytologic findings. A review of the medical literature revealed one previous cytologic description. The patient, A 53-year-old woman underwent surgery because of capsular contracture of textured, silicone breast implants. During surgery, 5 ml of peri-implant fluid collection fluid and the fibrotic capsules were submitted for pathologic analysis. The fluid was dense and smears showed abundant mucoid material that distributed on the background as a thick layer showing a wrinkled, "plastic food wrap" pattern. Numerous ball-like, three-dimensional spherical structures with a very well-defined contour were present. At low power magnification they created a worrisome cytologic image. Spherules consisted of cells embedded in a fibrous extracellular matrix. Cells showed round to oval nuclei with no pleomorphism. In the outer part of the spherules oval to spindle nuclei, parallel to the surface were evident. Histology of the resected capsules revealed remarkable papillary synovial metaplasia in addition to fibrosis and silicone deposition. In our opinion the spherules observed on cytology correspond to detached papillary fragments of synovial metaplasia. Their cytologic features are characteristic enough to permit a specific recognition avoiding misinterpretations. Pathologists must consider this diagnostic possibility whenever evaluating breast peri-implant fluid accumulations.