Fine-needle aspiration cytology of subcutaneous fat necrosis of the newborn: the cytology spectrum with review of the literature.

Subcutaneous fat necrosis of the newborn is a rare, transient panniculitis of full-term infants. Diagnosis is usually made clinically; however, a biopsy is sometimes required. Fine-needle aspiration biopsy (FNAB) offers an alternative to biopsy. The cytology shows a spectrum of changes ranging from clumped lobules of fat with opaque cytoplasm to necrotic aspirates with dispersed fat cells with opaque cytoplasm, foamy macrophages, multinucleated giant cells, lymphocytes, and neutrophils. Radially orientated, refractile, needle-shaped crystals are visible in the cytoplasm of the fat cells and loose lying in the necrotic background. FNAB offers an alternative to biopsy with good results.