Nevus Lipomatosus Superficialis in a Serous Inflammatory Capsule: A Case Report.

BACKGROUND Nevus lipomatosus superficialis (NLS) is a rare benign hamartomatous lesion characterized by adipocyte infiltration into the dermal layer of the skin. Clinically, there are 2 types of NLS lesions: the classical type and the solitary type. The solitary type of NLS is significantly more common in women, typically presents after age 30 years, and occurs most often in the inner thighs. This lesion is often mistaken for similar cutaneous lesions, including but not limited to acrochordons, fibrolipoma, neurofibromatosis, and lymphangioma. There is limited information in the literature on unique presentations of this rare lesion. CASE REPORT We present a case of a 26-year-old woman worried about a pedunculated papule in a fluid-filled capsule on her right inner thigh. She reported that the lesion doubled in size within 48 h prior to presentation. The lesion was biopsied in the clinic and pathology showed lobules of adipose cells in the dermis surrounded by collagen fibers and vascularity consistent with a diagnosis of inflamed NLS. Upon follow-up 2 weeks later, there were no signs of recurrence. CONCLUSIONS It was hypothesized that the unique presentation of a fluid-filled capsule surrounding a nevus lipomatosus superficialis occurred acutely following torsion of the pedunculated lesion. In addition to the patient's history of frictional rub between the thighs, histologic signs of lymphocytic infiltration in the dermis and edematous stroma supported the claim of torsional origins. The unique presentation of NLS in a fluid-filled capsule is not often discussed in the literature, and we hope this report will aid providers in identifying such lesions in the clinic.