American Journal of Dermatopathology:
Letters to the Editor
Nevus Lipomatosus Superficialis With Dilated Hair Follicles: An Epithelial Component in Hamartomatous Nevoid Skin Anomalies
Lee, Woo Jin MD*; Park, Oun Jae MD†; Won, Chong Hyun MD, PhD†; Chang, Sung Eun MD, PhD†; Lee, Mi Woo MD, PhD†; Choi, Jee Ho MD, PhD†; Moon, Kee Chan MD, PhD†
*Department of Dermatology, The Armed Forces Hongcheon Hospital, Hongcheon, Korea
†Department of Dermatology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
The authors declare no conflicts of interest.
To the Editor:
Nevus lipomatosus superficialis (NLS) is a rare hamartomatous nevoid skin anomaly characterized by aggregates of mature, ectopic adipose tissue in the dermis. We describe 2 patients with NLS showing dilated hair follicles. These features are unique compared with typical clinical findings in patients with NLS.
A 20-year-old man presented with soft coalescing papules and nodules located on his left buttock and waist, first observed 10 years earlier. The lesions consisted of several soft, flesh-colored papules and nodules having coarse cerebriform surfaces, with some of the lesions having dilated hair follicle–like plugs (Fig. 1, bold arrow). Three months earlier, the patient noticed the development of soft subcutaneous nodules around preexisting coalescing papular lesions (Fig. 1, dashed arrow). A skin biopsy was taken from 2 lesions, an earlier papular lesion with a dilated hair follicle–like plug and a recently developed subcutaneous nodule. Histopathologic examination of the papular lesion showed aggregates of ectopic adipose tissue on the dermis, around the vessels and sweat glands, and between the collagen bundles (Fig. 2A). There was a cystically dilated hair follicle with infundibular keratinization lining, filled with keratin materials and connected with epidermal surface (Fig. 2B). There was no evidence of hyperplasia of the sebaceous gland or the pilosebaceous unit. Histopathologic examination of the subcutaneous nodule showed clumps of adipose tissue embedded within the collagen bundles of the papillary dermis (Fig. 2C). More than half of the reticular dermis was replaced by ectopic adipose tissue. Histopathologic examination of these 2 lesions established a diagnosis of NLS with dilated hair follicles.
A 21-year-old man visited our clinic with a slowly enlarging, flesh-colored plaque on his left lower back of 15-year duration. Physical examination revealed linearly distributed soft plaques containing confluent lobulated papules with a cerebriform surface and occupying a 10 × 8-cm-sized area (Fig. 3). The lesions were covered with dilated hair follicle–like plugs but without any inflammatory signs, such as purulent discharge or swelling. The patient did not complain of any discomfort related to the lesions. There were no neurological abnormalities or evidence of any systematic disease. Histopathologic examination showed an infiltration of ectopic adipose tissue around the capillaries and between collagen bundles (Fig. 4A). Infiltrated adipose tissue occupied approximately 10% of dermal tissue in the extracted specimen. The fat cells on the dermis showed no evidence atypia, although their size was uneven. The dermis contained a cystic space lined with infundibular keratinized squamous epithelial cells (Fig. 4B). There was no hyperplasia of the cutaneous appendages. Based on these clinical and histopathologic findings, the patient was diagnosed with NLS with dilated hair follicles.
Clinically, NLS is usually present at birth but may develop during the first 3 decades of life. Two subtypes, a solitary form and a classic or multiple form, have been reported since this entity was first described.1,2 The lesions in the classic form are usually flesh-colored or yellow, smooth-surfaced papules or nodules, with femoral or gluteal location and in a zonal or segmental arrangement.2,3
NLS has been found to have various clinical features, including a cerebriform shape,4,5 peau d'orange surface, and hairiness.2,3 In addition, NLS has been associated with other types of skin lesion, including folliculosebaceous cystic hamartoma, dermoid cyst,6 and connective tissue nevus.7 To our knowledge, there has been only one previous report of NLS presenting with dilated hair follicles or comedo-like plugs.8 A case of NLS with a folliculosebaceous cystic hamartoma showing cystically dilated hair follicles has been reported.9 However, there was no hyperplasia of the sebaceous gland in presenting cases. Although the exact mechanism underlying the formation of a dilated hair follicle in patients with NLS is not known, follicular keratinocyte may be a part of hamartomatous nevoid skin anomalies in patients with NLS. Dilated hair follicle may represent an epithelial component in NLS.
NLS with dilated hair follicles should be differentiated from nevus comedonicus, a rare developmental abnormality of the pilosebaceous apparatus, which presents as plaques consisting of aggregated dilated follicular orifices in a linear pattern.10 Differentiation between these 2 entities is important because nevus comedonicus can occur in combination with other systemic abnormalities, such as skeletal and neurological disorders.11 Skin biopsy is important in the differentiation between NLS and nevus comedonicus. In contrast to NLS, nevus comedonicus does not present with ectopic adipose tissue in the dermis. However, the proportion of dermal fat in NLS has been found to vary from less than 10% to more than 50% of the dermis.12 NLS with dilated hair follicles and little ectopic adipose tissue may be confused with nevus comedonicus.
In conclusion, we have described 2 patients with unique features of NLS, dilated hair follicles. An exact diagnosis with histopathology is important because NLS has a broad variety in the clinical feature.
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