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

A Multicenter Study Validates the WHO 2022 Classification for Conjunctival Melanocytic Intraepithelial Lesions With Clinical and Prognostic Relevance

Several nomenclature and grading systems have been proposed for conjunctival melanocytic intraepithelial lesions (C-MIL). The fourth "WHO Classification of Eye Tumors" (WHO-EYE04) proposed a C-MIL classification, capturing the progression of noninvasive neoplastic melanocytes from low- to high-grade lesions, onto melanoma in situ (MIS), and then to invasive melanoma. This proposal was revised to the WHO-EYE05 C-MIL system, which simplified the high-grade C-MIL, whereby MIS was subsumed into high-grade C-MIL. Our aim was to validate the WHO-EYE05 C-MIL system using digitized images of C-MIL, stained with hematoxylin and eosin and immunohistochemistry. However, C-MIL cases were retrieved from 3 supraregional ocular pathology centers. Adequate conjunctival biopsies were stained with hematoxylin and eosin, Melan-A, SOX10, and PReferentially expressed Antigen in Melanoma. Digitized slides were uploaded on the SmartZoom platform and independently scored by 4 ocular pathologists to obtain a consensus score, before circulating to 14 expert eye pathologists for independent scoring. In total, 105 cases from 97 patients were evaluated. The initial consensus diagnoses using the WHO-EYE04 C-MIL system were as follows: 28 benign conjunctival melanoses, 13 low-grade C-MIL, 37 high-grade C-MIL, and 27 conjunctival MIS. Using this system resulted in 93% of the pathologists showing only fair-to-moderate agreement (kappa statistic) with the consensus score. The WHO-EYE05 C-MIL system (with high-grade C-MIL and MIS combined) improved consistency between pathologists, with the greatest level of agreement being seen with benign melanosis (74.5%) and high-grade C-MIL (85.4%). Lowest agreements remained between pathologists for low-grade C-MIL (38.7%). Regarding WHO-EYE05 C-MIL scoring and clinical outcomes, local recurrences of noninvasive lesions developed in 8% and 34% of the low- and high-grade cases. Invasive melanoma only occurred in 47% of the cases that were assessed as high-grade C-MIL. This extensive international collaborative study is the first to undertake a comprehensive review of the WHO-EYE05 C-MIL scoring system, which showed good interobserver agreement and reproducibility.

Conjunctival Melanocytic Lesions

CONTEXT.—

Conjunctival melanocytic lesions consist of a variety of neoplastic and nonneoplastic conditions. These include benign processes such as primary intraepithelial hypermelanosis and melanocytic hyperplasia, secondary forms of intraepithelial hypermelanosis and melanocytic hyperplasia, melanocytic nevi, melanocytic proliferations with malignant potential, and melanoma.

OBJECTIVE.—

To provide a concise yet comprehensive resource regarding the histopathologic diagnosis of conjunctival melanocytic lesions. We aim to detail and clarify the numerous classification schemes that exist for junctional melanocytic proliferations of the conjunctiva (known as primary acquired melanosis or PAM; also termed conjunctival melanocytic intraepithelial neoplasia or C-MIN). Although not uniformly adopted, C-MIN is classified by using a numeric system based on a defined set of criteria. A less complex scheme (conjunctival melanocytic intraepithelial lesion or CMIL) has recently been proposed by the World Health Organization. Additionally, we aim to update the reader regarding molecular features and prognostic indicators.

DATA SOURCES.—

Peer-reviewed literature and archived cases for illustration.

CONCLUSIONS.—

Accurate histologic classification is essential, as PAM/C-MIN/CMILs that have a significant potential to progress to invasive melanoma may be clinically indistinguishable from low-risk lesions. Conjunctival melanoma (CM) more closely resembles cutaneous melanoma in terms of its pathogenesis and molecular features, compared to melanoma arising at other mucosal sites or to uveal melanoma. Depth of invasion and ulceration status, among other factors, have emerged as important prognostic indicators in CM. Sentinel lymph node biopsy may provide further prognostic information. Lastly, integration of pathologic and clinical findings is essential at this anatomically sensitive location to determine appropriate clinical management.

Primary acquired melanosis/melanoma: utility of conjunctival map biopsy

AIM

To assess the role of map biopsy in patients with conjunctival primary acquired melanosis (PAM)/melanoma.

METHODS

Retrospective case series of 400 conjunctival biopsy samples of 51 unique patients in a tertiary referral centre.

RESULTS

Each patient underwent one diagnostic biopsy and several additional map biopsies (range 2-7) providing a total of 400 samples for the analysis (55 diagnostic biopsies, 345 map biopsies). The median age was 63 years old (range 20-88) with women representing 67% of the cases. Histopathological findings were graded as negative for melanosis/normal (grade 0), melanosis without atypia (grade 1), melanosis with mild atypia (grade 2), melanosis with severe atypia (grade 3) or invasive melanoma (grade 4). Clinicopathologic concordance was observed in the majority of the map biopsies (313, 91%) (positive: clinical+/path+ (57,17%), negative: clinical-/path- (256, 74%)). Three discordant samples (clinical-/path+) represented PAM sine pigmento. The histopathological spectrum of atypia was absent (40, 73%) or limited (11, 20%) in the majority of cases with tendency to cluster as low-grade or high-grade atypia. Map biopsy led to the identification of six patients (11%) with severe atypia, requiring topical mitomycin (MMC). Similarly, in 29 cases, periodic observation without topical MMC was recommended. One case of invasive melanoma transformation occurred in the MMC-treated group.

CONCLUSIONS

Map biopsy enhances overall assessment of the anatomic and pathologic extent, impacting use of adjuvant topical chemotherapy. In absence of map biopsy, it would be impossible to diagnose PAM sine pigmento. Additional corroborative work is needed to validate our observations.

Immunohistochemical Profiling of Conjunctival Melanocytic Intraepithelial Lesions, Including SOX10, HMB45, Ki67, and P16

PURPOSE

To determine the usefulness of melan-A, SOX10, HMB45, and p16 immunohistochemical stains in the distinction between the low-grade and high-grade conjunctival melanocytic intraepithelial lesions, either independently or as components of an immunohistochemical panel.

DESIGN

Retrospective observational case series.

METHODS

Institutional pathology records between 2014 and 2018 were searched for all patients with conjunctival melanocytic intraepithelial lesions. Biopsies without supporting clinical history or tissue available for review and immunohistochemical analysis were excluded. Clinical, histopathologic, and immunohistochemical (p16, SOX10, HMB45, and Ki-67) findings were recorded.

RESULTS

Thirty-one patients underwent 47 biopsies for conjunctival melanocytic lesions between 2014 and 2018. Pathologic diagnoses were low-grade conjunctival melanocytic intraepithelial lesion (n = 18, 38%) and high-grade conjunctival melanocytic intraepithelial lesion/melanoma in situ (n = 29, 62%). The addition of melan-A and SOX10 immunohistochemical stains resulted in an upgrade of conjunctival melanocytic intraepithelial lesion from low-grade to high-grade in 2 (4%) of 47 cases. The addition of melan-A and SOX10 immunohistochemical stains did not downgrade any of the histomorphologically high-grade lesions. In a clinical-pathologic multivariable model, the parameters most predictive of high-grade melanocytic intraepithelial lesion/melanoma in situ were involvement of the caruncle (odds ratio [OR] = 19, confidence interval [CI] 1.6-212; P = .02] and p16 cytoplasmic H-score >30 (OR = 81, CI 2.7 to >999; P = .01) CONCLUSION: Although the stains for melanocytic markers melan-A and SOX10 facilitate assessment of melanocytic intraepithelial lesions, the current immunohistochemical panels have limited value in distinction between the low-grade and high-grade intraepithelial melanocytic proliferations and need to be used judiciously.

Immunohistochemical analysis of benign and malignant melanocytic lesions of the conjunctiva using double-staining

OBJECTIVE

To implement a double-staining technique to identify the most sensitive and specific combinations of melanoma antigen recognized by T cells (Melan-A), microphthalmia-associated transcription factor (MITF), human melanoma black 45 (HMB45), and Ki67 aiming to assist in the diagnosis of atypical melanocytic conjunctival lesions that are more prone to malignant progression.

METHODS

Eight specimens of conjunctival melanoma and of primary acquired melanosis with moderate to severe atypia were double-immunostained with a combination of a cytoplasmic marker (anti-Melan-A or anti-HMB45), and a nuclear marker (anti-MITF or anti-Ki67). Eight specimens of normal conjunctiva and of conjunctival nevi served as controls. The specimens were processed using 3,3-diaminobenzidine substrate for nuclear stains and the fast-red substrate for cytoplasmic stains. Each slide was analyzed by light microscopy and provided a percent scale and a 0 to 4+ score for each nuclear and cytoplasmic component.

RESULTS

Melan-A and MITF were strongly positive markers for all melanocytic cells, whereas Ki67 and HMB45 provided a variable response for identifying potentially proliferative or aggressive cells. HMB45 and MITF proved to be the best combination for differentiating between atypical and benign lesions on a percent scale and a 0 to 4+ scale (p = 0.0004), with the 3 other combinations providing mainly confirmatory diagnostic information (p < 0.05).

CONCLUSIONS

Our study used an immunohistochemical double-staining approach to differentiate between atypical and benign melanocytic lesions of the conjunctiva. Our findings should aid in a more complete immunohistopathological diagnosis of conjunctival melanocytic lesions, particularly in diagnostically difficult cases.

[Focus on clinical and pathological management of conjunctival melanocytic tumors]

Conjunctival-pigmented tumors are rare, but they are one of the most commonly encountered by the pathologist working with the department of ophthalmology. Nevus and melanoma can be encountered and have some histological difference compared to their cutaneous counterpart. Primary acquired melanosis (PAM) is a conjunctival specific entity. This clinical term includes several histological lesions ranging from benignity to melanoma precursor lesion. Histologic examination determines the therapy and the risk of progression to melanoma. We present here a histopathological, clinical and therapeutic synthesis of conjunctival-pigmented lesions, emphasizing the importance of a good understanding between clinicians and pathologists.

Update on conjunctival pathology

Conjunctival biopsies constitute a fairly large number of cases in a typical busy ophthalmic pathology practice. They range from a single biopsy through multiple mapping biopsies to assess the extent of a particular pathological process. Like most anatomical sites, the conjunctiva is subject to a very wide range of pathological processes. This article will cover key, commonly encountered nonneoplastic and neoplastic entities. Where relevant, sections will include recommendations on how best to submit specimens to the ophthalmic pathology laboratory and the relevance of up-to-date molecular techniques.

Traumatic iridial extrusion mimicking a conjunctival melanocytic neoplasm

Conjunctival melanoma is a rare malignant tumour of the eye. Its diagnosis represents a challenge for general pathologists due to low exposure to ocular biopsies and a broad differential diagnosis. In addition, conjunctival samples are often small and are associated with a high frequency of artefacts due to their processing. Here, we present the first case to date of a traumatic iridial extrusion masquerading as a conjunctival melanocytic neoplasm. An 83-year-old Asian man presented with a conjunctival-pigmented nodule surrounded by an area of diffuse pigmentation. Histopathology revealed in the nodule a well-demarcated lesion composed of spindle shaped melanocytes with thick-walled blood vessels. At higher magnification, the blood vessels were composed of thick walls with collagen fibres in an onion-skin-like arrangement. The histological findings were consistent with extruded iridial tissue. The map biopsies of the flat, pigmented lesion showed melanocytic cell proliferation with dendritic processes restricted to the lamina propria without any epithelial involvement, consistent with ocular melanocytosis. The diagnosis of conjunctival melanocytic lesions is challenging, and non-neoplastic conditions should always be included in the differential diagnosis. Pathologists should correlate clinicopathological findings and be familiar with the normal histology in order to achieve the correct diagnosis.

Conjunctival Primary Acquired Melanosis: Is It Time for a New Terminology?

PURPOSE

To review the diagnostic categories of a group of conditions referred to as "primary acquired melanosis."

DESIGN

Literature review on the subject and proposal of an alternative diagnostic schema with histopathologic and immunohistochemical illustrations.

METHODS

Standard hematoxylin-eosin-stained sections and immunohistochemical stains for MART-1, HMB-45, microphthalmia-associated transcription factor (MiTF), and Ki-67 for calculating the proliferation index are illustrated.

RESULTS

"Melanosis" is an inadequate and misleading term because it does not distinguish between conjunctival intraepithelial melanin overproduction ("hyperpigmentation") and intraepithelial melanocytic proliferation. It is recommended that "intraepithelial melanocytic proliferation" be adopted for histopathologic diagnosis. Atypical proliferations are characterized either by bloated dendritic melanocytes with enlarged cell components (dendrites, cell bodies, and nuclei) or by epithelioid melanocytes without dendrites. Atypical polygonal or epithelioid pagetoid cells may reach higher levels of the epithelium beyond the basal layer. Immunohistochemistry defines the degree of melanocytic proliferation or the cellular shape (dendritic or nondendritic) (MART-1, HMB-45) or identifies the melanocytic nuclei (MiTF). Intraepithelial melanocytic proliferation without atypia represents increased numbers of normal-appearing dendritic melanocytes (hyperplasia or early neoplasia) that generally remain confined to the basal/basement membrane region. Intraepithelial nonproliferative melanocytic pigmentation signifies the usually small number of conjunctival basal dendritic melanocytes that synthesize increased amounts of melanin that is transferred to surrounding keratinocytes.

CONCLUSION

All pre- and postoperative biopsies of flat conjunctival melanocytic disorders should be evaluated immunohistochemically if there is any question regarding atypicality. This should lead to a clearer microscopic descriptive diagnosis that is predicated on an analysis of the participating cell types and their architectural patterns. This approach is conducive to a better appreciation of features indicating when to intervene therapeutically. An accurate early diagnosis should forestall unnecessary later surgery.

Current appraisal of conjunctival melanocytic tumors: classification and treatment

Conjunctival melanocytic tumors represent a spectrum of pigmented tumors that include benign, premalignant and malignant tumors. Conjunctival nevi are the most common pigmented tumors and are typically found in the interpalpebral bulbar conjunctiva. These lesions usually contain fine clear cysts on slit lamp biomicroscopy. Primary acquired melanosis includes lesions from increased melanin pigmentation without proliferation of melanocytes to melanoma in situ. In the new classification system, the idea is to use the term 'primary acquired melanosis' only as a clinical description, highlighting the fact that the biologic behavior of acquired melanotic lesions cannot be predicted solely based upon clinical grounds without histopathologic examination. Conjunctival melanoma represents only 5% of all melanomas arising in the ocular region and is associated with a high mortality rate. The management of primary acquired melanosis, nevi and conjunctival melanomas involves various modalities used either alone or concomitantly depending on the size and extent of the lesion.

Ophthalmic pterygium: a stem cell disorder with premalignant features

Pterygia are common ocular surface lesions thought to originate from limbal stem cells altered by chronic UV exposure. Traditionally regarded as a degenerative condition, pterygia also display tumor-like features, such as a propensity to invade normal tissue and high recurrence rates following resection, and may coexist with secondary premalignant lesions. This study was initiated to determine the rate of concurrent ocular surface diseases in patients with pterygia recruited from the practice of a single surgeon operating in a Sydney metropolitan hospital. One hundred pterygium specimens were histopathologically reviewed and selected cases were immunohistochemically assessed to confirm diagnosis. Along with previously documented typical features including epithelial proliferation, goblet cell hyperplasia, angiogenesis, inflammation, elastosis, stromal plaques, and Bowman's membrane dissolution, we identified five cases of ocular surface squamous neoplasia, six cases of primary acquired melanosis, two compound nevi (one suspect invasive melanoma), and one dermoid-like lesion. In 18 specimens, clusters of basal epithelial cells that coexpressed cytokeratin-15/-19 and p63-α were identified at the head of the pterygium, coinciding with clinical observation of Fuchs' flecks. Our data show that significant preneoplastic lesions may be associated with pterygium and that all excised pterygia should undergo histological examination. The presence of p63-α-positive epithelial cell clusters supports the hypothesis that pterygia develop from limbal epithelial progenitors.

Melanocytic Lesions of the Conjunctiva

Context—Melanocytic proliferations are among the most common neoplasms of the conjunctiva. They often represent challenging lesions for pathologists unfamiliar with unique histologic features of melanocytic proliferations in this location and with nomenclature used by ophthalmologists.

Objective—To comprehensively review clinical aspects, pathologic features, and management of melanocytic proliferations of the conjunctiva.

Data Sources—Review of the literature and personal experience of the authors.

Conclusions—Classification, state of the art, and practical aspects of pathology of melanocytic proliferations of the conjunctiva are discussed.

Recurrent primary acquired melanosis with atypia involving a clear corneal phacoemulsification wound

PURPOSE

To report a case of corneal primary acquired melanosis (PAM) with atypia after cataract surgery.

METHODS

Retrospective case report with literature review.

RESULTS

Excision of an elevated pigmented conjunctival lesion was performed at the time of cataract extraction by clear corneal phacoemulsification by an outside surgeon. Histopathologic examination revealed PAM with atypia. Three months after the initial surgery, recurrent melanosis involving the peripheral corneal epithelium was noted, with extension of pigment into the corneal stroma through the paracentesis site. Excision of the involved corneal epithelium and the adjacent conjunctiva was performed, and microscopically recurrent PAM with atypia was confirmed. Adjuvant cryotherapy was applied at the time of surgery, and topical mitomycin C was given postoperatively. Repeat biopsies revealed no remaining malignancy, and the intrastromal pigment has disappeared during 18 months of follow-up.

CONCLUSION

We present this case to illustrate the importance of complete evaluation and treatment of potentially atypical melanocytic conjunctival lesions before proceeding with elective intraocular surgery.

Boston Ocular Surface Prosthesis for persistent epitheliopathy after treatment of conjunctival melanoma

PURPOSE

To report two cases of persistent epitheliopathy after treatment of conjunctival melanoma and review management options for this condition.

METHODS

Case report and literature review.

RESULTS

Persistent epitheliopathy, presumably resulting from limbal stem cell deficiency, is an uncommon complication of treatment of conjunctival malignant melanoma with surgical excision, cryotherapy, and mitomycin C. The Boston Ocular Surface Prosthesis was successful in improving vision, comfort, and epithelial status in our patients.

CONCLUSION

Persistent epitheliopathy is a rare complication of treatment of conjunctival melanoma. The Boston Ocular Surface Prosthesis is a viable treatment option in this situation.

[Suspicious conjunctival lesions]

The main conjunctival tumors are represented by (i) conjunctival melanoma, ocular surface squamous neoplasia, and conjunctival lymphoma, which are malignant tumors, and (ii) conjunctival nevus, papilloma, and choristoma, which are benign. In usual practice, ophthalmologists need to know how to differentiate conjunctival melanomas and carcinomas from the other conjunctival tumors by clinical examination. Indeed, the therapeutic approach to these two malignant diseases presents a number of particularities such as the need for surgery under general anesthesia, if possible, to minimize the risk of local dissemination and further local recurrence, and detailed information on the tumor location and measurements before surgery (Figures, diagram, sizes) to precisely define the irradiation field during complementary radiotherapy. The clinical signs and main therapeutic principles of conjunctival tumors are reviewed in this article.

Ocular surface tumors

Tumors of the conjunctiva and cornea comprise a large and varied spectrum of conditions. These tumors are grouped into two major categories of congenital and acquired lesions. The acquired lesions are further subdivided based on origin of the mass into surface epithelial, mucoepidermoid, melanocytic, vascular, fibrous, neural, histiocytic, myxoid, myogenic, lipomatous, lymphoid, leukemic, metastatic and secondary tumors. Ocular surface tumors include a variety of neoplasms originating from squamous epithelium, melanocytic tumors and lymphocytic resident cells of the conjunctival stroma. In this review, we highlight clinical features of these lesions, important diagnostic and investigative tools and standard care of management.