Atlas of Dermatopathology
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
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
. 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.
. Val-Bernal JF, González-Vela MC. Cutaneous lipomatous neurofibroma: characterization and frequency 2005;32 (4):274–279.
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. Solam L, Hana B, Ku AS. Liponeurofibroma: clinicopathological features and histogenesis. J Dermatol 2018;45 (4):416–424.