Trichilemmoma Arising in the Nasal Vestibule: Report of Three Cases with Special Emphasis on the Differential Diagnosis

Abstract

Trichilemmoma is a benign cutaneous epithelial tumor with differentiation towards cells of the outer hair root sheath and usually presents as a small papule on the face of middle-aged or older adults. We herein report three cases of trichilemmoma located in the nasal vestibule, including two of the conventional type and one of the desmoplastic variant. To our knowledge, only one case of trichilemmoma arising in the nasal vestibule has been previously reported. Trichilemmoma must be included in the differential diagnosis of epithelial lesions arising in this location. This is particularly important in the case of the desmoplastic trichilemmoma, a tumor that resembles invasive carcinoma such as desmoplastic squamous cell carcinoma, sclerosing basal cell carcinoma, and trichilemmal carcinoma. The circumscription of the lesion, the architectural pattern of epithelial cell cords and small nests merging with a desmoplastic stroma in the central area of the tumor, the expression of CD34, and the lack of an obvious squamous differentiation or basaloid foci favor the diagnosis of desmoplastic trichilemmoma. All these features help to rule out the diagnosis of carcinoma with significant clinical implications.

Introduction

Trichilemmoma was first described by Headington and French [1] as a clear cell tumor with differentiation towards the outer hair root sheath. It consists of superficial lobules of glycogen-rich epithelial cells with peripheral palisading of columnar cells, surrounded by a thickened basement membrane. Trichilemmomas may be solitary or multiple. The solitary variant usually arises as a small, warty or smooth, skin-colored papule on the face of middle-aged or old adults [2]. Multiple trichilemmomas are associated with Cowden syndrome [3]. In 1990, Hunt et al. [4] described a histologic variant of trichilemmoma that contains an area of narrow irregular cords of epithelial cells entrapped in a dense eosinophilic hyaline stroma resembling invasive carcinoma. It was called desmoplastic trichilemmoma. As a manifestation of their differentiation towards the outer sheath of the hair root, trichilemmomas, both conventional and desmoplastic types express CD34, a feature that has been used in their differential diagnosis with other epithelial tumors [5–7].

Despite the frequent location of trichilemmoma on the skin of the nose, to our knowledge, only one case arising in the nasal vestibule has been published to date [8]. We hereby report three cases of trichilemmoma of the nasal vestibule. Its recognition is important for the differential diagnosis of epithelial lesions in this location.

Materials and Methods

Three cases with the diagnosis of trichilemmoma and located in the nasal vestibule were retrieved from the files of the Department of Pathology of the Hospital Universitario de Fuenlabrada. All specimens were shave biopsies. Hematoxylin-eosin, PAS and PAS-diastase stains were studied. Immunohistochemical evaluation was performed on paraffin-embedded tissue using the EnVision detection system (Dako, Glostrup, Denmark) and an anti-CD34 antibody (clone: QBend-10; dilution: 1/50; source: Dako).

Results

The clinical data are summarized in Table 1. All three patients were male. The ages at the time of the diagnosis ranged from 38 to 74 years. The lesions were noticed between 5 and 12 months prior to the first consultation. They presented as asymptomatic whitish papules in the nasal vestibule, except in Case 1, which reported occasional nose bleeding. All three lesions were located in the nasal vestibule, of which two were right-sided and one was left-sided. Their sizes ranged from 3 to 10 mm. The patients revealed no other cutaneous lesions. Clinical working diagnoses included angiofibroma, verruca vulgaris, and fibroma. Shave biopsy of the lesion was performed in all cases.

Table 1.

Case data

	Case 1	Case 2	Case 3
Age (years)	54	38	74
Gender	Male	Male	Male
Size (mm)	4	3	10
Clinical symptoms	Nose bleeding	Asymptomatic	Asymptomatic
Evolution time (months)	6	5	12
Clinical diagnosis	Angiofibroma	Verruca vulgaris	Verruca vulgaris/Fibroma
Pathological diagnosis	Trichilemmoma	Trichilemmoma	Desmoplastic trichilemmoma

Histopathologically, the tumors consisted of lobules of epithelial cells in continuity with the epidermis and the hair follicles (Fig. 1). The lobules showed pushing, well-demarcated margins (Fig. 2). The cells were polygonal and exhibited oval to round, uniform nuclei and clear, glycogen-rich cytoplasm (Figs. 3 and 4). A palisade of columnar cells limited the epithelial lobules, which were surrounded by a thickened, diastase-resistant, PAS-positive basement membrane (Fig. 5). In the central area of Case 3, the epithelial cells were arranged in small nests and cords embedded in an eosinophilic dense stroma (Fig. 6). The tumor cells expressed CD34 in the three lesions (Fig. 7). The epidermis showed hyperkeratosis with parakeratosis. The pathologic diagnosis was trichilemmoma in all cases, with Case 3 being called the desmoplastic variant (desmoplastic trichilemmoma).

Fig. 1.

Low magnification view of a trichilemmoma showing a tumor lobule connected to the epidermis (Case 2)

Fig. 2.

A trichilemmoma exhibiting its pushing and well-demarcated deep margin (Case 2)

Fig. 3.

High magnification of trichilemmoma revealing epithelial cells with oval, bland nuclei and clear cytoplasm (Case 1)

Fig. 4.

Tumor cells with numerous PAS-positive intracytoplasmic granules (Case 1) (PAS stain)

Fig. 5.

Intermediate magnification showing palisading of low columnar cells in the periphery of a tumor lobule, surrounded by a thickened basement membrane (Case 1)

Fig. 6.

Small tumor nests with irregular margins within a dense stroma in the center of a desmoplastic trichilemmoma (Case 3) (PAS-diastase stain)

Fig. 7.

Tumor cells of a trichilemmoma showing a diffuse cytoplasmic expression of CD34 (Case 1). Notice the CD34-positive endothelial cells in the adjacent dermal vessels

Discussion

Our cases met the diagnostic criteria of trichilemmoma. To our knowledge, only one trichilemmoma of the nasal vestibule has been previously reported. It was diagnosed in a 49-year-old male with a history of nasal congestion, snoring, nasal obstruction, and nose bleeds and consisted of a 1 cm, rubbery, non-tender, polypoid mass arising from the lateral aspect of the right nasal vestibule [8]. Trichilemmoma in this location is probably more frequent than may be inferred from the literature data. We think that it may be frequently misdiagnosed as another type of epithelial tumor. Its recognition is particularly important in the case of the desmoplastic variant, which simulates invasive carcinoma.

The differential diagnosis of trichilemmoma in the nasal vestibule includes verruca vulgaris, other benign hair follicle or epidermal tumors, and, in the desmoplastic variant, squamous carcinoma, sclerosing basal cell carcinoma, and trichilemmal carcinoma. The relationship between trichilemmoma and verruca vulgaris is controversial. In fact, verrucae are not rare in the nasal vestibule. In addition, trichilemmomas are often clinically diagnosed as verrucae and trichilemmoma-like areas may be sometimes histologically found in common warts. Some authors believe that trichilemmomas are merely old verrucae with trichilemmal differentiation [9]. However, most studies have failed to detect human papillomavirus in trichilemmomas [10, 11]. Several types of benign epithelial tumors with hair follicle or epidermal differentiation, such as trichofolliculoma [12], inverted follicular keratosis [13], keratoacanthoma [14], seborrheic keratosis [15] or condyloma acuminatum [16] have been reported in the nasal vestibule and must be included in the differential diagnosis. However, all of these present with distinctive architectural patterns and, unlike trichilemmomas, lack clear cells and a thick basement membrane.

More important is the distinction between desmoplastic trichilemmoma and several types of carcinoma. Trichilemmal carcinoma shows ill-defined margins and moderate to marked cytologic atypia, lacks the typical stroma of desmoplastic trichilemmoma and presents an architectural pattern reversed to that of desmoplastic trichilemmoma, with the invasive lobules located at the periphery of the tumor. Desmoplastic squamous carcinoma and sclerosing basal cell carcinoma lack the circumscription of desmoplastic trichilemmoma and present a random distribution of cell cords; moreover, the invasive nests lack a preference for the central area of the lesion as shown by desmoplastic trichilemmoma. In addition, the tumor cells of these carcinomas do not usually express CD34 [5, 6]. The presence of nests of conventional trichilemmoma and the absence of an obvious squamous differentiation and basaloid foci lend further support to the diagnosis of desmoplastic trichilemmoma.

In conclusion, we hereby present three cases of trichilemmoma of the nasal vestibule, one of them of the desmoplastic variant, a rarely documented lesion that must be included in the differential diagnosis of epithelial tumors in this location. Particularly important is to distinguish desmoplastic trichilemmoma from desmoplastic squamous cell carcinoma, sclerosing basal cell carcinoma, and trichilemmal carcinoma due to the clinical impact of these differential diagnoses.