Fine-needle aspiration biopsy of subcutaneous fat necrosis of the newborn.

This report provides the first description of the fine-needle aspiration biopsy findings in a case of subcutaneous fat necrosis of the newborn. While initial interpretation of the aspirate smears was suspicious for a neoplastic process, subsequent incisional biopsy confirmed the benign nature of the lesion. Review of the cytologic material revealed rare, negatively stained, needle-shaped crystals within histiocytes and multinucleate giant cells. In the appropriate clinical setting, and given a mixture of lymphocytes, histiocytes, and multinucleate giant cells in the aspirate smears, we believe the finding of negatively stained needle-shaped crystals can strongly suggest the diagnosis of subcutaneous fat necrosis of the newborn.