Limbal schwannoma: Clinicopathological study of a case with review of literature.

Schwannomas involving the perilimbal conjunctiva is an extremely rare clinical entity and has been reported scantily in literature. In this case, a 27-year-old healthy female presented with a pinkish smooth globular mass involving the limbus in the superonasal quadrant of the left eye. The mass was completely excised and histopathology revealed an encapsulated tumor, with cells displaying elongated nuclei, bland chromatin, and few Verocay bodies with palisaded nuclei, suggestive of schwannoma. Immunohistochemistry showed strong S100 positivity. This case thus highlights schwannoma as a differential diagnosis of limbal masses. Copyright:

Introduction

Limbal masses are of various histological types, the most common being dermoids, epitheliomas, papillomas, and nevi. Tumors of the limbus more commonly involve the squamous epithelium. The substantia propria of the conjunctiva contains various vascular, fibrous, neural, and myogenic elements. Although rare, the limbus may be affected by benign and malignant growths arising from these structures. Neural tumors involving the limbus are neurofibromas, neurilemmomas (schwannomas), and granular cell tumors. Schwannomas involving the orbit are more common from an ophthalmological point of view, although rarely intraocular schwannomas may arise from the ciliary nerves within the uvea and sclera. Conjunctival schwannomas are extremely rare. We report a case of conjunctival schwannoma with the review of literature.

Case Report

A 27-year-old female presented with a history of a limbal mass involving the left eye [Figure 1a]. The mass had gradually been increasing in size over the duration of 1 year. There was no history of pain, dimness of vision, antecedent trauma, any other systemic illness, or any similar episode in the past affecting either eye. There was no significant family history.

Figure 1

(a) External photograph showing a smooth globular pinkish mass at the limbus in the superonasal quadrant, (b) histopathological section showing Verocay bodies, and (c) fascicles of bland spindle cells

On examination, best-corrected visual acuity was 6/6 in both the eyes. Lids and periocular skin was normal. A solitary, globular pinkish mass of 5 mm × 5 mm, with regular margins and smooth surface, was noted in the limbal region in the superonasal quadrant. The mass was soft in consistency and it encroached upon the cornea for approximately 1 mm. Few prominent conjunctival vessels were present in the surrounding bulbar conjunctiva which were seen converging toward the mass. The intraocular pressure and ocular movements were normal. The cornea was otherwise clear, anterior chamber was of normal depth, and pupillary reactions and fundus were within normal limits. Systemic examination was normal.

Ultrasound biomicroscopy showed no infiltration into the anterior chamber angle. Hemogram was within normal limits.

Excision biopsy was done and histopathological reports showed an encapsulated tumor composed of alternating hypercellular and hypocellular areas. The tumor cells displayed elongated nuclei, bland chromatin, indistinct nucleoli, and moderate amount of cytoplasm. Few Verocay bodies with palisaded nuclei were also seen [Figure 1b and c]. The findings were suggestive of schwannoma. There was no evidence of malignancy. Immunohistochemistry showed diffuse strong cytoplasmic positivity for S100 [Figure 2] and was negative for cytokeratin, smooth muscle actin, desmin, and HMB45.

Figure 2

The tumor cells show diffuse strong cytoplasmic positivity for S100. (a) S100: low-power view, (b) S100: high-power view, and (c) MIB-1 labeling index of ~1%

At follow-up, the wound healed well and the patient had no further complaints.

Discussion

Schwannoma of the conjunctiva is a benign tumor that may arise from the bulbar, forniceal, or palpebral conjunctiva.[1] It is an encapsulated tumor found in isolation or in association with von Recklinghausen disease. The tumor arises due to proliferation of Schwann cells of the peripheral nerve sheath and is composed of spindle cells in Antoni A or Antoni B pattern. Immunohistochemistry is helpful in diagnosing certain cases, with the tumor staining positively for S100. Anti-neurofilament antibody and HMB-45 staining is negative in schwannoma. Treatment involves complete surgical excision with the capsule.

Dabezies and Penner reported a case in a Caucasian woman of 50 years age.[2] The mass located in the bulbar conjunctiva in the upper temporal quadrant of the left eye was first noticed by the patient at 11 years, which then increased in size gradually. The mass was surgically excised. Le Marc'hadour et al. described a case of conjunctival schwannoma in a 37-year-old male patient.[3] The tumor was located in the left eye and on ultrastructural analysis was composed of Schwann cells showing S100 positivity. Another report suggestive of schwannoma located lateral to the caruncle has been reported in a 12-year-old girl by Vincent and Cleasby.[4] The mass underwent excision without recurrence.

Only a single case of conjunctival schwannoma was reported in a 61-year-old male in a review of 2455 conjunctival tumors by Grossniklaus et al.[5]

Charles et al. reported three cases of conjunctival neurilemmomas of presumed ciliary nerve origin.[1] The first was a 19-year-old female with a pedunculated mass in the inferior fornix of left eye. The second case was a 26-year-old female with an asymptomatic epibulbar mass located at 6'o clock position in the right eye. In the third case, a 72-year-old female presented with a painless mass in the left upper eyelid, which led to eversion of the eyelid. The mass was 10 mm × 10 mm in size and involved the tarsal conjunctiva. Surgical excision was performed in all three cases with an uneventful postoperative course.

Andreoli et al. in their report described a perilimbal mass, provisionally diagnosed as a pingueculum, in a 68-year-old male patient.[6] The mass was located in the left eye at 3'o clock position. Excision was performed with no evidence of scleral extension. Histology revealed regions suggestive of Antoni A and B patterns. The tumor cells were S100 positive and HMB-45 negative.

Ohshima et al. reported a temporal palpebral mass in the left eye of a 10-year-old female patient.[7] The mass underwent excision with tumor cells showing S100 positivity.

Demirci et al. described an epibulbar mass in the superonasal quadrant in the left eye of a 17-year-old boy.[8] The mass underwent excision and cryotherapy applied to surrounding conjunctiva. Immunohistochemistry showed S100 positivity.

Nair et al. documented a nontender conjunctival mass in a 12-year-old boy.[9] The mass was located at 5'o clock position of the left eye and was prominent on dextroelevation. The mass was excised and cryotherapy applied. Antoni A and Antoni B areas and “picket fence pattern” nuclear arrangement with S100 positivity were seen.

Alam et al. reported a painless epibulbar mass in a 17-year-old Indian male patient located in the left inferotemporal bulbar conjunctiva.[10] The mass was excised and the conjunctiva was apposed by electrocautery. Spindle cells with Verocay bodies and strong S100 positivity were noted.

Literature review thus describes schwannomas over a wide range of age groups, with no gender predilection. Involvement of the perilimbal area has been described on only two occasions earlier by Andreoli et al. and Charles et al. Hence, although rare, schwannoma may present as a perilimbal conjunctival mass, and a complete surgical excision, without grafting, may be sufficient treatment, as in our case.

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Conflicts of interest

There are no conflicts of interest.