Verrucous trichoadenoma - presenting as discharging sinus on face.

Sir,

Trichoadenoma is a slowly growing follicular tumor, which is rare, benign, well differentiated and solitary. It was first described by Nikolowski in 1958.[1] It occurs equally in men and women. The lesions present as a non-specific nodule. The commonest sites of appearance are face, buttocks.[2]

We want to discuss a case of 28-year-old female patient who presented with a swelling on right cheek with discharge since last 2 years [Figure 1]. Since then patient had been taking treatment for same in the form of antibiotics and anti-inflammatory drugs but there was no relief. She had even undergone incision and drainage few times for the same. On clinical examination there was a single nodular lesion measuring 2 cm × 1 cm with discharge on surface. Examination of buccal mucosa of same site did not reveal any lesion. We kept a differential diagnosis of lupus vulgaris, deep fungal granuloma.

Figure 1

Nodular lesion with scarring and discharge on right cheek

Routine laboratory blood investigations were normal. Mantoux test was non-reactive. Pus culture and examination did not reveal any growth either bacterial or fungal. AFB staining of pus was negative. Punch biopsy was taken and sent for histopathological examination.

Histopathological examination of the tissue showed epidermis with hyperplasia and keratotic plugging [Figure 2]. In the dermis many horn cysts were present surrounded by eosinophillic cells. Fibrous tissue around cysts was increased at few sites [Figure 3]. Infiltration by chronic inflammatory cells consisting of lymphocytes and plasma cells was seen. At few sites sebaceous differentiation was also seen. Based on above histological findings, a diagnosis of verrucous trichoadenoma was made and the lesion was excised surgically.

Figure 2

10X view of histopathological section showing hyperplastic 0epidermis and keratotic plugging [H & E, 10×]

Figure 3

40X view of section showing multiple horn cysts [H & E, 40×]

Trichoadenoma is a benign tumor of hair follicle, presenting as a solitary nodule on face (58%) or buttocks (25%), size may vary from 3 to 50 mm in diameter. Rarely it can be present on neck, arms, thighs, shoulder, and shaft of penis.[3] It may arise any time during adult life in both sexes equally.[2345] Few case reports of childhood and congenital onset has also been described.[6]

Microscopic study of trichoadenoma reveals multiple horn cysts throughout dermis, surrounded by eosinophillic epithelial cells. The central cystic cavity shows epidermoid keratinization and looks like the cross section of infundibular portion of pilosebaceous canal without any evidence of hair follicle formation. Solid epithelial islands of eosinophillic epithelial cells without central keratinization can also be seen.[257]

In morphological differentiation trichoadenoma is believed to be in between trichoepithelioma and trichofolliculoma, differentiating toward infundibular portion of pilosebaceous canal.

Trichoepithelioma is an autosomal dominant disorder; histologically, it is characterized by the presence of islands of basaloid cells with peripheral palisading and surrounded by dense fibroblastic stroma.[25]

At the other end, trichofolliculoma is a benign hamartomous lesion that can develop at any age. Histologically, trichofolliculomas consist of a centrally located, unilocular or multilocular keratin filled cystic cavity with hair shaft fragments, lined by infundibular squamous epithelium with prominent granular layer.[25]

In our case the clinical appearance of lesion with discharge was very misleading. Histopathological examination proved to be very helpful in diagnosing this case. The lesion had been excised completely without any recurrence so far.