A 70-year-old Caucasian man presented with a several-month history of a solitary, asymptomatic papule on the left eyebrow. Physical examination demonstrated a solitary 5-mm smooth, dome-shaped skin colored papule with subtle central erosion on the left eyebrow. No overlying telangiectasias were noted. A biopsy of the lesion was performed. The lesion was composed of plump spindle cells arranged in a plexiform pattern in the background of thick, keloidal collagen bundles. The lesional cells were NKI/C3-positive and S-100-negative. A diagnosis of cellular neurothekeoma was made.
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| Figure 1 |
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| Figure 1. A skin-colored papule is present on the left eyebrow. |
A 70-year-old Caucasian man presented with a several-month history of a solitary, asymptomatic lesion on the left eyebrow. His medical history included stage 1A lentigo maligna melanoma and multiple non-melanoma skin cancers. Physical examination demonstrated a solitary 5-mm smooth, dome-shaped skin colored papule with subtle central erosion on the left eyebrow (Fig. 1). No overlying telangiectasias were noted.
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| Figure 2 | Figure 3 |
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| Figure 2. Well-defined fasicles and nests of epithelioid tumor cells arranged in a plexiform pattern and set in a dense kelloidal
stroma are present (H&E, x400) Figure 3. High power examination showing the lesional cells are positive for NKI/C3, supporting the diagnosis of cellular neurothekeoma (x100). |
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A biopsy of the lesion was performed and stained with hematoxylin-eosin (Fig. 2), NKI/C3 (Fig. 3). Histopathologic examination of the skin biopsy specimen revealed a nodular dermal lesion with a surrounding epidermal collarette. The lesion was composed of plump spindle cells arranged in a plexiform pattern in the background of thick, keloidal collagen bundles. The spindle cells have abundant grey cytoplasm and round nuclei with focally prominent nucleoli. Cellular atypia and mitoses were not identified. Immunohistochemical stains show the lesional cells to be positive for NKI/C3 (Fig. 3) and negative for S100 and CD163 (unpublished observations). The lesion was excised.
Neurothekeoma, a term coined by Gallager and Helwig in 1980 [1], is a benign, cutaneous neoplasm first described by Harkin and Reed in 1969 as "nerve sheath myxoma" [2]. Since their initial description, it has been recognized that a histologic spectrum exists for these lesions. At one end of the spectrum is the classic nerve sheath myxoma, which shows true peripheral nerve sheath differentiation and is accordingly S100-positive. The cellular variant of neurothekeoma represents the other end of the spectrum and was described by Rosati et al. in 1986 and further defined in Barnhill and Mihm's 1990 case series [3, 4]. As the name suggests, they are hypercellular when compared to the myxoid variant. Further contrasting between the two, cellular neurothekeomas are S100-negative and remain to be fully defined with respect to their origin.
Data from the largest case series to date demonstrate that these lesions are most commonly skin-colored to erythematous papules or nodules typically measuring <2 cm in diameter, most commonly presenting on the extremities or in the head and neck region [5]. Classically, these lesions demonstrate a female predominance (ratio 1.8:1) and present during the first three decades of life (mean age 25 years), although a wide age range has been reported.
Histologically, cellular neurothekeomas are composed of epithelioid and somewhat spindled cells arranged in lobulated nests and fascicles in the dermis. The stroma may be thick and collagenized and, as seen in this case, may appear keloidal in nature. When these lesions show such a densely collagenized stroma, the term 'desmoplastic cellular neurothekeoma' has been proposed [6]. They can also mimic neural, fibrohistiocytic, or melanocytic neoplasms, including melanoma. Atypical histologic features such as nuclear pleomorphism, mitoses, vascular invasion, and subcutaneous extension may be present, although they have no prognostic significance. Cellular neurothekeomas are often positive by immunohistochemistry for NKI-C3 (100%), NSE (89%), and SMA (57%) and are consistently S100-negative [5]. This latter feature is of assistance in differentiating this lesion from the neural and melanocytic lesions in the morphologic differential diagnosis. The lack of an epidermal component also assists the distinction from a melanocytic process. Furthermore, melanocytic markers such as HMB-45 and Melan-A are negative in cellular neurothekeoma.
© 2009 Dermatology Online Journal