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Nevus lipomatosus cutaneous superficialis with perifollicular fibrosis

European Journal of Dermatology. Volume 13, Number 6, 584-6, November - December 2003, Clinical report

Summary

Author(s) : Hideki TAKASHIMA, Masahiko TOYODA, Yoko IKEDA, Masayori KAGOURA, Masaaki MOROHASHI , Department of Dermatology, Faculty of Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930‐0194, Japan. .

Summary : Nevus lipomatosus cutaneous superficialis (NLCS) is a rare hamartomatous skin lesion histopathologically characterized by the presence of mature fat tissue even within the upper dermis. Clinically, two types of NLCS can be distinguished\; a multiple type and a solitary type. We here report a 10‐month‐old girl showing multiple type NLCS as a collection of a nodule and papules on her right abdomen. Histological examination revealed that the lesion was composed of a lobular proliferation of fat tissue throughout the dermis and immature hair follicle‐like structures with perifollicular fibrosis. Histological alterations of the dermal connective tissue components were also seen, including thickening of collagen bundles and increased numbers of both fibroblasts and blood vessels. This is the first reported case of NLCS with perifollicular fibrosis.

Keywords : connective tissue nevus, nevus lipomatosus cutaneous superficialis, perifollicular fibroma.

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ARTICLE

Auteur(s) : Hideki TAKASHIMA, Masahiko TOYODA, Yoko IKEDA, Masayori KAGOURA, Masaaki MOROHASHI

Department of Dermatology, Faculty of Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194, Japan.

Article accepted on 11/8/03

Nevus lipomatosus cutaneous superficialis (NLCS) is a rare hamartomatous skin lesion that is usually seen at birth but that can arise at any other time within the first two decades of life. The first case to be identified as NLCS was reported by Hoffmann and Zurhelle in 1921 [1, 2]. Clinically, two types of NLCS can be distinguished, the multiple and the solitary. The multiple type shows groups of skin-colored or yellowish soft papules or nodules with smooth or wrinkled surfaces. This type tends to appear in the lumbar region, buttocks, and thigh [1]. The lesions are usually unilateral and sometimes occur in a linear, band-like, or zosteriform distribution. The solitary type, on the other hand, involves a single papule or nodule that usually appears not at birth but later within the first twenty years, and shows no favored location. There is no sexual predilection or hereditary trend. No abnormalities are associated with either type.
Perifollicular fibroma (PF) was first reported in 1925 by Burnier and Rejsek and in 1960 was defined as an entity by Zackheim and Pinkus [3]. PF is characterized by a hamartomatous proliferation of the pilar connective tissue sheath. One of its histological features is the presence of layers of cellular fibrous tissue in a perifollicular arrangement. PF occurs predominantly on the scalp, face, neck, or upper trunk and in either solitary or multiple form. Solitary PF can be either congenital or acquired, whereas multiple PF has been suggested to exhibit an autosomal dominant trait and has been associated with internal diseases such as colon cancer [4, 5]. It also has been suggested that multiple PFs may be identical to the Birt-Hogg-Dubé syndrome [6].
Histologically, NLCS is characterized by the development of lobules of mature fat tissue within the dermis. Histological abnormalities of the dermal connective tissue components, the epidermis, and the appendages have also been reported in some instances [1]. No cases have been reported of NLCS having perifollicular fibrosis similar to that occurring in perifollicular fibroma. We here report a case of multiple type NLCS histopathologically accompanied by perifollicular fibrosis.

Case report

A 10-month-old Japanese girl visited our university hospital with the complaint of a nodule on the abdomen that had been developing since several days after birth. According to her parents, the nodule was initially a single lesion but had developed, within the girl's first 3 months, into several papules on the right lateral side of the initial nodule. There was no known history of any minor trauma or repeated irritations to the affected site. Her family history was noncontributory.
Physical examination revealed a 15 mm soft, elastic, skin-colored nodule on the lateral side of the right lower abdomen. The nodule was dome-shaped and its surface was uneven (Fig. 1). Additionally, a number of tiny skin-colored papules were found adjacent to the right side of the nodule, and several normal skin- to brown-colored papules, measuring approximately 2 to 3 mm, were also seen 1 cm from the upper right side of the nodule. She had a small angioma on the scalp from birth. She was otherwise healthy and had no systemic complaints. The results of routine laboratory examinations were all within normal ranges. The tentative clinical diagnosis of the lesions was either epidermal nevus, connective tissue nevus, or a cutaneous appendageal tumor. The lesions were surgically excised under general anesthesia. No local recurrence has been noted in 17 months of follow-up.
Histologically, the nodule had slight papillomatosis. The characteristic features of the nodule were groups of fat cells embedded among the collagen bundles of the dermis and immature follicular structures surrounded by densely cellular fibrous tissue (Fig. 2, 3). The fat lobules were irregularly distributed in the reticular dermis, extending into the subpapillary dermis. There was continuity between the dermal and subcutaneous fat tissue. The fibroblasts within the lesion increased in number throughout the dermis, especially in the papillary dermis, perifollicular connective tissue areas, and collagen bundles surrounding ectopic fat tissue. The numbers of small blood vessels and capillaries were moderately increased in the papillary and upper reticular dermis. A few vessels surrounded by fat cells were seen in the subpapillary dermis (Fig. 4). Infiltration of inflammatory cells was sparse throughout the lesion. The small papules also had ectopic fat tissue in the dermis as well as follicular structures surrounded by dense layers of fibrous connective tissue. Immunohistochemical staining was strongly positive for vimentin in the papillary dermis and perifollicular connective tissue areas. Alcian blue staining revealed a marked increase in the amount of mucopolysaccharides in the perifollicular connective tissue areas as well as the papillary dermis. An elastic van Gieson stain showed a marked decrease in elastic fibers in the perifollicular connective tissue areas.

Discussion

Clinically, our patient had a nodule and many papules confined to a circumscribed area of the abdomen. Histologically, the lesion had ectopic fat tissue in the dermis and immature follicular structures surrounded by dense proliferation of cellular connective tissue. From this clinical feature and the histology of ectopic fat tissue in the dermis, the lesion is considered to be almost entirely consistent with those of multiple type NLCS, although NLCS does not usually include perifollicular fibrosis. Except for the finding of ectopic fat tissue in the dermis, our case might be diagnosed as a localized form of multiple perifollicular fibromas. In PF, however, there were originally thought to be no special histological abnormalities except for its characteristic perifollicular fibrosis. Furthermore, although perifollicular fibrosis similar to PF could be observed in fibroma of tuberous sclerosis [8], fibrous papule of the face [9], and fibrofolliculoma [6, 10], our case is obviously different from these diseases. Therefore, we finally diagnosed our case as NLCS with perifollicular fibrosis.
In NLCS, histological abnormalities of the dermal connective tissue components, the epidermis, and the appendages have also been reported [1]. These include thickening of collagen bundles, alteration of elastic fiber, increased numbers of fibroblasts and blood vessels, infiltration of mononuclear cells around the capillaries, acanthosis, papillomatosis, abortive hair germ structures and dilated follicular ostia. However, pilosebaseous changes have not been histologically reported so far. There has been no reported case of NCLS with perifollicular fibrosisis, although there was one case report of NCLS with follicular papules and hypertrophic pilosebaceous units [11].
The pathogenesis of NLCS remains unknown. To date, it was presumed that the ectopic fat tissue in the dermis is derived from the perivascular mesenchymal tissue [1]. An electron microscopic study of NLCS [12] also supported this concept, as it revealed the close proximity of the fat cells to blood vessels and the differentiation of immature lipoblasts into mature fat cells. In our case, vessels surrounded by fat cells were seen in the subpapillary dermis. Therefore, it is tempting to speculate that at least some ectopic fat cells in our case may be derived from the perivascular mesenchymal tissue. As to PF, its pathogenesis was presumed to be either a fibroma representing adnexal tumors of the skin arising de novo by proliferation of the connective tissue sheath of the hair follicle, or a fibroblastic response to previous inflammation [3]. Because our case began almost from birth and grew progressively, and because there was no previous inflammation and little, histologically, in the way of inflammatory cell infiltration, we presumed that our case of perifollicular fibrosis was not a fibroblastic response to previous inflammation but rather was of nevoid origin. The immature hair follicle-like structure also suggested a nevoid origin.
In a broad sense, a connective tissue nevus is a hamartoma consisting of connective tissue components of the skin including not only the extracellular matrix but also other connective tissue components, such as fat tissue or cellular elements [13]. In fact, Pierard and Lapiere [14], in their classification of connective tissue nevus, included NLCS in a nevus of reticular connective tissue and PF in a nevus of adventitial connective tissue. According to this concept, our case may be one of connective tissue nevi with unique characteristics, including the excess of dermal fat and the perifollicular connective tissue. To the best of our knowledge, this is the first reported case of NLCS with perifollicular fibrosis. n

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