Trichoblastoma of the eyelid: Rare or underdiagnosed!

INTRODUCTION

Trichoblastoma (TBL) is a rare benign, slow-growing tumor of the skin and adnexa. It was first described by Headington in 1970^[1] and was further classified by Ackerman et al.^[2] It is asymptomatic, slow-growing and found mostly in the head-and-neck region. The eyelid and adnexa are rare sites for the tumor. The main differential diagnosis for the same is basal cell carcinoma (BCC), as the treatment modalities for the two differ. Hence, differentiation between the two based on histopathology becomes important. Here, we present a TBL of the lower eyelid seen in a 65-year-old male.

CASE REPORT

A 65-year-old male presented to the eye department with complaints of a slow-growing mass over the left lower eyelid for the past 1 year. It was gradual in onset, painless, and progressive in nature and not associated with any sudden increase in size. He did not give a history of any other similar swelling in the past or in any other part of the body. He is a known diabetic on oral hypoglycemic agents.

On examination, there was a well-defined firm nodular mass below the left lower eyelid measuring around 4 mm in diameter. The nodule was pigmented, ulcerated, and non-umbilicated, with well-defined margins [Figure 1]. It was non-tender. The rest of the eye examination was within normal limits. The nodular mass was excised under local anesthesia using Radiofrequency cautery and was sent for histopathological evaluation. Postoperatively, the wound was healthy and healed with minimal scarring [Figure 2].

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Figure 1: Preoperative photograph showing a nodular left lower eyelid mass.

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Figure 2: Postoperative photograph following lid mass excision.

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Histopathological examination revealed a well-demarcated dermal tumor with normal overlying epidermis. The lesion predominantly comprised epithelial cells arranged in nests with peripheral palisading. The individual cells contained eosinophilic cytoplasm and regular basophilic nucleus with inconspicuous nucleoli. Mild cellular pleomorphism was noted. Moderately dense lymphocytic infiltrate was present along with melanophages [Figure 3]. No evidence suggestive of invasive pathology in the form of atypia or mitosis was seen. The features were suggestive of a benign adnexal tumor of follicular differentiation. Based on the above findings, a diagnosis of TBL was made.

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Figure 3: Histopathological image of lesion with hematoxylin and eosin stain at 10x magnification.

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DISCUSSION

TBLs are slow-growing, benign tumors which originate from follicular germinative cells. They were first described by Headington in 1970.^[1] It was Ackerman who further differentiated it to include all follicular neoplasms.^[2] The exact incidence and prevalence of TBL worldwide are not known. They are seen mostly in middle-aged adults with a predominance in males.

The tumor is well circumscribed, sporadic, frequently solitary and arises from the hair follicle. They are generally <2 mm in diameter. However, sizes between 5 and 8 mm have been seen.^[3] The skin overlying the mass is hyperpigmented, ulcerated, and alopecic. They have commonly been seen in the head-and-neck region. TBL in the periocular region is very rare and underdiagnosed.

Very few case reports of TBL of the periocular region have been reported to date.^[3-9] There is one large retrospective case series involving 15 patients reported by Chowdhury et al.^[10] The salient features of the cases reported are shown in Table 1.

Out of the eight reported cases, only two have been reported in the Indian population. The age group of the patients ranges from 40 to 79 years. Of the eight cases, 5 have been reported in females and 3 in males. The lesions have been localized to the upper or lower eyelid or the inner canthus.

The main differential diagnosis to be considered in these cases is BCC. BCC originates from basal cells of the epidermis. However, there are rare subtypes such as infundibulocystic BCC, which are derived from hair follicle-derived cells.^[11] BCC is a locally invasive tumor, whereas TBL rarely undergoes a malignant transformation into trichoblastic carcinoma.

Histologically, BCC shows clefts between the epithelium and stroma in contrast to TBL, where the clefts are within the periepithelial stroma and the surrounding dermal collagen. BCC, being an invasive tumor, shows mitoses, apoptotic bodies, mucinous stroma, or amyloid deposits. Immunohistochemistry can also be used to differentiate the two in cases of a diagnostic dilemma. TBL has B-cell lymphoma 2 expression in the basaloid keratinocytes in the outermost layer. However, BCC shows diffusive staining. Cluster of Differentiation 34 (CD) and CD10 are expressed only in the peritumoral stromal cells in the case of TBL, while intraepithelial staining is a feature of BCC. However, in this case, histology was sufficient to confirm the diagnosis and further immunochemistry studies were not performed.

CONCLUSION

TBL is a rare and underdiagnosed eyelid lesion which needs to be differentiated from the more invasive BCC. Hence, clinicians need to be aware of this entity. Furthermore, histopathological diagnosis becomes very important in these cases to decide the line of management. Complete surgical excision prevents further chance of recurrence. This case highlights a rare eyelid lesion which has been reported from a peripheral center with limited diagnostic facilities.