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Atlas of Dermatopathology

Liponeurofibroma

Shao, Ya-Kun; Chang, Jian-Min

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International Journal of Dermatology and Venereology: June 2022 - Volume 5 - Issue 2 - p 119-120
doi: 10.1097/JD9.0000000000000175
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Histopathology

A liponeurofibroma is a dermal neurofibroma (NF) with an infiltration of abnormal fat cells. Under HE staining, the liponeurofibroma lesion is a well-circumscribed and nonencapsulated tumor mass located in the dermis. Spindle-shaped tumor cells with wavy cytoplasm and elongated nuclei are scattered in the tumor mass. Fatty change is clearly seen inside the tumor, replacing the S- shaped cells. Round fat cells with vacuolated cytoplasm and thin nuclei are larger than the surrounding cells and may gather and fuse into clusters, while some adipocytes have intraluminal flap-like structures (Fig. 1). Compared with deep subcutaneous fat cells, tumor adipocytes are smaller, fewer in number, and vary in size. Liponeurofibromas are classified as focal infiltrating (5.6%) and diffuse infiltrating (1.3%, regularly interspersed).1 The incidence of such fatty changes range from 6.9% to 24.6%.2-3

F1
Figure 1:
Histopathological examination of cutaneous liponeurofibroma. (A) A well-circumscribed and nonencapsulated tumor mass located in the dermis. The center of the tumor contains scattered fatty tissue (HE staining, 40 ×). (B) Round fat cells with vacuolated cytoplasm and thin nuclei are larger than the surrounding cells. Some adipocytes have intraluminal flap-like structures (HE staining, 100 ×). (C) Fatty change replaces some of the S-shaped and spindle-shaped tumor cells (HE staining, 200 ×).

Clinical features

Dermal NF is a benign peripheral nerve sheath tumor that presents as a solitary tumor in 90% of cases (Fig. 2). The remaining 10% of lesions are found in persons with an autosomal dominant genetically inherited disease called neurofibromatosis, sometimes accompanied by milk-coffee spots, acoustic neurilemomas, and intellectual abnormalities.1 Skin lesions can grow along nerve trunks. Initially, a solitary NF lesion usually occurs as a hard pimple and then gradually enlarges to a nodule with a smooth surface. The lesion varies from mung bean-sized to egg-sized, with varying degrees ofpigmentation. Some skin lesions have pedicles protruding over the peripheral skin surface. The skin lesions have a rubbery texture and remain soft, without causing pain or pruritus. Previous studies have reported some differences between liponeur-ofibroma and classic NF. Liponeurofibroma generally occurs in older patients than classic NF, while NF is more common in females and frequently develops in the head and neck area.1

F2
Figure 2:
Clinical appearance of cutaneous liponeurofibroma. A dome-shaped, well-circumscribed, and tender cutaneous nodule protruding over the peripheral skin surface. The nodule is light red in color and measures approximately 6 cm × 4 cm, without pedicles.

References

[1]. Muir D, Neubauer D, Lim IT. Tumorigenic properties of neurofibromin-deficient neurofibroma Schwann cells. Am J Pathol 2001;158 (2):501–513. doi: 10.1016/S0002-9440(10)63992-2.
[2]. Val-Bernal JF, González-Vela MC. Cutaneous lipomatous neurofibroma: characterization and frequency 2005;32 (4):274–279.
[3]. Solam L, Hana B, Ku AS. Liponeurofibroma: clinicopathological features and histogenesis. J Dermatol 2018;45 (4):416–424.
Copyright © 2022 Hospital for Skin Diseases (Institute of Dermatology), Chinese Academy of Medical Sciences, and Chinese Medical Association, published by Wolters Kluwer, Inc.