Low-risk and High-risk Histologic Features in Conjunctival Primary Acquired Melanosis With Atypia: Clinicopathologic Analysis of 29 Cases

Abstract

The current World Health Organization classification of conjunctival melanocytic proliferations divides them into conjunctival nevi and invasive melanoma but, in contrast to other anatomic sites, does not recognize melanoma in situ. All atypical intraepithelial conjunctival proliferations are included in a heterogeneous category designated as primary acquired melanosis (PAM) with atypia. We performed clinicopathologic analysis of 29 cases of PAM with atypia. On the basis of histologic features and frequency of association with invasive melanoma and metastases, we were able to divide our cases into 2 histologic groups. The low-risk group (13 cases) included lesions composed of small to medium size melanocytes with high nuclear to cytoplasmic ratio and small to medium size hyperchromatic nuclei devoid of nucleoli showing predominantly single cell lentiginous growth pattern. Invasive melanoma occurred in only 2 cases from this group. None of these lesions metastasized. The second, high-risk group (16 cases), showed increased frequency of association with invasive melanoma (15/16 cases, 94%) and metastases (4/16 cases, 25%). These lesions were more heterogeneous architecturally but were all composed of melanocytes showing various degrees of epithelioid features such as abundant cytoplasm, vesicular nuclei, or prominent nucleoli. In 4 cases discrete areas showing high-risk and low-risk features were identified. All 4 lesions were associated with invasion. Our findings offer a practical approach for prognostically useful subclassification of PAM with atypia, which emphasizes cytologic features of intraepithelial conjunctival melanocytic proliferation.

Pathologie oculaire conjonctivale. Étude rétrospective sur dix ans au CHU de Toulouse-Rangueil et revue de la littérature

“…Quarante-quatre pour cent des lésions pigmentées enlevées sont des naevi et environ 36 % sont des mélanomes [2]. Cependant, il faut replacer ces pourcentages dans le contexte d'une extrême rareté des mélanomes conjonctivaux ; les mélanomes oculaires étant essentiellement uvéaux [9].…”

“…Les origines de cette classification remontent à Zimmerman en 1966, qui nota l'évolution indolente de nombreuses prolifé-rations mélanocytaires atypiques conjonctivales [9].…”

“…Les difficultés diagnostiques se concentrent sur les mélanoses acquises primitives (appelées primary acquired melanosis [PAM] par les anglo-saxons) [9,10] et sur les naevi, qui prennent un aspect particulier dans la conjonctive [8]. Devant une lésion pigmentée de la conjonctive, l'attitude de l'ophtalmologiste sera de réaliser des photographies (ou de comparer avec des photographies antérieures du patient), afin d'assurer le suivi de l'évolution de la lésion.…”

“…Les mélanoses acquises primitives sont constituées par une prolifération mélanocytaire intraépithéliale chez une personne d'âge moyen ou avancé, à l'exclusion des naevi et des mélanomes [9]. Elles peuvent avoir ou non des atypies et ces deux cas sont cliniquement indistingables [11].…”

Melanose primária adquirida associada a erosões epiteliais recorrentes da córnea

“…Responde por aproximadamente 20 a 35% dos tumores conjuntivais pigmentados e o envolvimento corneano pode ser observado em cerca de 23% dos casos (2)(3)(4) . Histologicamente a MPA é classificada em dois tipos: MPA sem atipia, proliferação benigna de melanócitos normais restrita à camada basal da conjuntiva; e MPA com atipia, condição pré-maligna onde há aumento no número de melanócitos grandes, com nucléolos proeminentes e citoplasma abundante, podendo envolver todas as camadas da conjuntiva (crescimento pagetóide) (4,5) . Aproximadamente 13% dos casos de MPA conjuntival que apresentam atipias intensas evoluem para melanoma e cerca de 75% dos melanomas da conjuntiva evoluíram a partir de um quadro inicial de MPA (3,4) .…”