Local conjunctival metastases (LCMs) may represent under-recognized lesions arising from the dissemination of primary conjunctival melanoma via local vessels, suggest findings published in the British Journal of Ophthalmology.
Investigators Hardeep Mudhar (Royal Hallamshire Hospital, Sheffield, UK) and colleagues say that histopathologic detection of LCMs indicates a higher disease stage and may be a proxy indicator of the presence of non-conjunctival metastases, thus necessitating high-resolution radiologic imaging modalities or sentinel node biopsy.
The researchers retrospectively identified seven patients with 15 primary conjunctival melanomas who developed 19 LCMs during 2001-2010. Analysis of clinical data revealed that the LCM developed 8-102 months after the first primary melanoma, with non-conjunctival metastases developing 8-37 months after the first LCM among three patients.
LCMs showed some distinct histopathologic features, including that they were well defined, separated from the overlying epithelium by a Grenz zone, and were often multiple and associated with vessels and lymphocytic aggregates. While some appeared within the area of the vascular drainage territory of the primary melanoma, others did not.
Furthermore, the team notes that diffuse solid LCMs occurred mainly within the bulbar conjunctiva, while coalescing nodule LCM types were seen in the tarsal and forniceal conjunctivas.
The researchers stress that if conjunctival mapping biopsies do not reveal a primary conjunctival invasive melanoma, a search for a non-conjunctival primary melanoma should be undertaken.
"In our institution we see approximately 20 new cases of conjunctival melanoma per year, and so the question arises why LCM detection is very rarely reported in the literature… there is a possibility that previously reported melanomas of the conjunctiva with a nodular configuration may in fact be LCMs and therefore an under-recognized phenomenon," say Mudhar and team.
The researchers call for staining with Melan-A to examine for in situ melanoma or melanosis with atypia, as its absence should alert the pathologist to the possibility of a LCM.
"The presence of LCMs has staging implications and should be regarded as having N1 status in the TNM classification," conclude the authors.
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