Conjunctival Melanocytic Nevi


Conjunctival Nevus With Prominent Epithelial Cysts
Conjunctival melanocytic nevi (50%) can exhibit numerous epithelial-lined cysts image located within the lesion, as seen here under scanning magnification. This is a useful finding, supporting benignancy. Note the lymphohistiocytic infiltrate image hugging the lesion.



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Epithelial Cysts With Sulfur Granules
Higher power magnification shows the cysts to contain sulfur granules image and invoke a neutrophilic response image. The nested nevomelanocytes image, surrounding the infected cysts, are devoid any cytological atypia.

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Juvenile Conjunctival Nevus
At this scanning magnification, a hypercellular proliferation appears to occupy the subepithelium image underneath the conjunctival epithelium image. There is intralesional cystic degeneration image. There is a focus of intense lymphohistiocytic infiltrate image commonly seen in these lesions.

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Confluent Growth Pattern and Reverse Maturation
A higher magnification is shown from the same lesion. The subepithelial component does not appear to decrease in the nuclear:cytoplasmic ratio. This paradoxical maturation is an expected feature.


TERMINOLOGY


Abbreviations




• Conjunctival melanocytic nevus


Synonyms




• Acquired or congenital conjunctival nevi
• Primary acquired melanosis (PAM)

image Not secondary melanosis due to inflammation or systemic disease

image Should be distinguished from complexion-associated melanosis

– Which is found commonly in dark-skinned individuals and shows bilateral involvement


Definitions




• Benign melanocytic proliferation arising on conjunctiva

• Most common tumors of conjunctiva, accounting for up to 53% of all conjunctival neoplasms


CLINICAL ISSUES


Epidemiology




• Most common in young Caucasians, with mean age at presentation of ~ 32 years

• Juvenile conjunctival nevus occurs in children and adolescents

• PAM occurs in middle-aged or elderly Caucasians


Site




• Most commonly arise in bulbar conjunctiva, caruncle, or plica semilunaris

• PAM occurs on bulbar conjunctiva


Presentation




• Circumscribed flat to slightly raised macules or papules
image Presence of intralesional cysts

• Juvenile conjunctival nevi rapidly grow and can look clinically concerning, leading to biopsies

• PAM is acquired, usually unilateral, flat, pigmented lesion
image Melanosis can extend to skin if lesion involves palpebral conjunctiva

image Pigmentation in PAM may wax and wane and even disappear


Natural History




• Malignant melanoma can develop in less than 1% of conjunctival nevi


Treatment




• Surgical approaches
image Conjunctival nevi do not require treatment if clinically stable

• Excision or rebiopsy may be needed if there is change in size or color, or recurrence


Prognosis




• Conjunctival nevi have excellent prognosis

• PAM without atypia can recur in about 11% cases, but it does not progress to melanoma


MICROSCOPIC


Histologic Features




• Anatomic classification (similar to skin)
image Junctional: Nested but sometimes also lentiginous proliferations of type A or type B cells confined to epithelium

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Apr 24, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Conjunctival Melanocytic Nevi
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