Neutrophil-rich subcutaneous fat necrosis of the newborn: A potential mimic of infection.

BACKGROUND: The inflammatory infiltrate seen in biopsy specimens obtained from patients with subcutaneous fat necrosis of the newborn (SCFN) has classically been described as consisting mostly of histiocytes. However, we encountered patients with SCFN whose biopsy specimens revealed mostly neutrophils, prompting infection to be an initial consideration.

OBJECTIVES: We sought to describe cases of SCFN in which neutrophils formed the majority of the infiltrate at our institution and in the literature.

METHODS: We performed a retrospective analysis of patients with SCFN reported at our institution and a literature review of SCFN.

RESULTS: Thirteen cases of SCFN were identified at our institution. In 2 of 13 cases, neutrophils composed >75% of the inflammatory infiltrate, and both lesions were 1 day old. From the literature review, neutrophils were mentioned as a component of the infiltrate in 10 of 124 cases, but in none were neutrophils described as forming the majority of the infiltrate.

LIMITATIONS: This study is limited by its retrospective nature and small sample size.

CONCLUSIONS: Neutrophils can comprise most of the inflammatory cells in patients with SCFN, especially early in the course of the disease. This variant of SCFN can be easily mistaken for infection.