Inverted Mucoepidermoid Papilloma: A Case Report

Dear Editor,

Inverted mucoepidermoid papilloma is a rare benign epithelial tumor. There have been six cases reported worldwide and here, we would like to introduce the first case of the inverted mucoepidermoid papilloma of conjunctiva in Korea. Written informed consent for publication of the clinical images was obtained from the patient.

A 56-year-old man presented with right conjunctival mass found 2 months ago. He had no other underlying diseases except hypertension. His corrected visual acuity was 20/16 in both eyes. About 0.5 × 0.3-cm-sized pigmented and vascularized pedunculated mass was seen over the right inferior palpebral conjunctiva (Fig. 1A). The mass was soft and painless in nature.

Fig. 1

Photographs and histological images of the patient. (A) A pigmented, vascularized mass over the right inferior palpebral conjunctiva. (B) Histopathology of the mass revealed a single fragment lined by stratified squamous cells, with downward extension of conjunctival epithelium (H&E, ×40). (C) Cystic components in the lobules of nonkeratinizing squamous epithelium. Many goblet cells seen. No inflammation, dysplasia, and necrosis found (H&E, ×400). (D) Clear tarsal conjunctiva of the right lower lid after excisional biopsy.

An excisional biopsy was performed, and the brownish sample was measured 0.5 × 0.3 × 0.2 cm. Histopathologic examination showed a single fragment lined by stratified squamous cells, with downward extension of conjunctival epithelium (Fig. 1B, 1C). Cystic components were visible in the lobules of nonkeratinizing squamous epithelium. Many goblet cells were found. No definite evidence of inflammation, dysplasia, and necrosis was found. Heuring et al. [1] reported peripheral carcinomatous foci within the lesion in their case of inverted transitional cell papilloma, whereas there was no evidence of malignancy in this case. On follow-up examination, his tarsal conjunctiva of the right lower lid was clear without remaining pigmented lesion (Fig. 1D). No recurrence was reported in up to 6 months of follow-up.

Inverted papilloma is less common compared to exophytic papilloma in conjunctiva, with epithelium invaginating into the substantia propria endophytically. It is usually found in nasal cavity or paranasal sinuses, and there have been some case reports regarding local recurrence and malignant transformation of the tumor [2].

On histopathologic examination, inverted papilloma involving conjunctiva quite differ from inverted papilloma of other sites, featuring distinct cystic components within acanthotic lobules. Based on this finding, Jakobiec et al. [3] recommended the term inverted mucoepidermoid papilloma. Since inverted mucoepidermoid papilloma can be misdiagnosed as conjunctival nevus or malignant melanoma, definitive diagnosis should be made by histopathologic examination. There is no report on local recurrence or malignant transformation of inverted mucoepidermoid papilloma in conjunctiva, though there is no data on long-term follow-up of inverted mucoepidermoid papilloma over 5 years due to the rarity of the subtype [4].

In conclusion, we present a first case of inverted mucoepidermoid papilloma of conjunctiva in South Korea, which is an exceedingly rare neoplasm. Although inverted mucoepidermoid papilloma is extremely rare, it should be considered as a differential diagnosis of pigmented conjunctival mass.