Primary melanocytic tumors of the central nervous system: a review with focus on molecular aspects

Primary melanocytic tumors of the central nervous system (CNS) represent a spectrum of rare tumors. They can be benign or malignant and occur in adults as well as in children, the latter often in the context of neurocutaneous melanosis. Until recently, the genetic alterations in these tumors were largely unknown. This is in contrast with cutaneous and uveal melanomas, which are known to harbor distinct oncogenic mutations that can be used as targets for treatment with small-molecule inhibitors in the advanced setting. Recently, novel insights in the molecular alterations underlying primary melanocytic tumors of the CNS were obtained, including different oncogenic mutations in tumors in adult patients (especially GNAQ, GNA11) vs. children (especially NRAS). In this review, the focus is on molecular characteristics of primary melanocytic tumors of the CNS. We summarize what is known about their genetic alterations and discuss implications for pathogenesis and differential diagnosis with other pigmented tumors in or around the CNS. Finally, new therapeutic options with targeted therapy are discussed.

Melanotic tumors of the nervous system are characterized by distinct mutational, chromosomal and epigenomic profiles

Melanotic tumors of the nervous system show overlapping histological characteristics but differ substantially in their biological behavior. In order to achieve a better delineation of such tumors, we performed an in-depth molecular characterization. Eighteen melanocytomas, 12 melanomas, and 14 melanotic and 14 conventional schwannomas (control group) were investigated for methylome patterns (450k array), gene mutations associated with melanotic tumors and copy number variants (CNVs). The methylome fingerprints assigned tumors to entity-specific groups. Methylation groups also showed a substantial overlap with histology-based diagnosis suggesting that they represent true biological entities. On the molecular level, melanotic schwannomas were characterized by a complex karyotype with recurrent monosomy of chromosome 22q and variable whole chromosomal gains and recurrent losses commonly involving chromosomes 1, 17p and 21. Melanocytomas carried GNAQ/11 mutations and presented with CNV involving chromosomes 3 and 6. Melanomas were frequently mutated in the TERT promoter, harbored additional oncogene mutations and showed recurrent chromosomal losses involving chromosomes 9, 10 and 6q, as well as gains of 22q. Together, melanotic nervous system tumors have several distinct mutational and chromosomal alterations and can reliably be distinguished by methylome profiling.

The WHO 2018 Classification of Cutaneous Melanocytic Neoplasms: Suggestions From Routine Practice

The "multidimensional" World Health Organization (WHO) classification 2018 of melanocytic tumors encompasses nine melanoma pathways (seven of which for cutaneous melanoma) according to a progression model in which morphologically intermediate melanocytic tumors are cosidered as simulators and/or precursors to melanoma. These "intermediates" can be subclassified into: i) a "classical" subgroup (superficial/thin compound: dysplastic nevus), which is placed within the morphologic and molecular progression spectrum of classical (Clark's and McGovern's) melanoma subtypes (superficial spreading and, possibly, nodular); and ii) a "non-classical" subgroup (thick compound/dermal: "melanocytomas") whose genetic pathways diverge from classical melanoma subtypes. Such a progression model is aimed at giving a conceptual framework for a histopathological classification; however, routine clinicopathological practice strongly suggests that most melanomas arise de novo and that the vast majority of nevi are clinically stable or even involuting over time. Clinicopathological correlation can help identify some severely atypical but benign tumors (e.g.: sclerosing nevus with pseudomelanomatous features) as well as some deceptively bland melanomas (e.g.: lentiginous melanoma; nested melanoma), thereby addressing some ambiguous cases to a correct clinical management. The recently available adjuvant therapy regimens for melanoma raise the problem of a careful distinction between severely atypical (high grade) melanocytoma and "classical" melanoma: conventional morphology can guide an algorithmic approach based on an antibody panel (anti-mutated BRAF, BAP1, PRAME, ALK, TRKA, MET, HRAS-WT, ROS; beta catenin; R1alpha; p16; HMB45; Ki67), a first-line molecular study (identification of hot spot mutations of BRAF and NRAS) and an advanced molecular study (sequencing of NF1, KIT, BRAF, MAP2K1, GNAQ, GNA11, PLCB4, CYSLTR2, HRAS; fusions studies of BRAF, RET, MAP3K8, PRKCA); as a final step, next-generation sequencing can identify melanocytic tumors with rare genetic signatures and melanocytic tumors with a high tumor mutation burden which should be definitely ascribed to the category of classical melanoma with the respective therapeutic options.

Melanocytomas of the central nervous system: a clinicopathological and molecular study

BACKGROUND

Melanocytomas of the Central Nervous System (CNS) are rare and benign lesions. These slow-growing tumours can behave aggressively, with local recurrence. Various genetic aberrations occur in malignant melanomas and raise possible new therapeutic options. However, little information is available regarding these characteristic genetic alterations in melanocytomas of the CNS. This study was designed to better understand the clinicopathological and molecular features of melanocytomas.

MATERIALS AND METHODS

Twenty cases of melanocytoma were studied by light microscopy, electron microscopy and immunohistochemistry. Clinical characteristics, therapeutic options and prognosis were analysed. BRAF, NRAS and KIT gene mutations were tested by direct DNA sequencing.

RESULTS

Fourteen of twenty patients had intracranial tumours including one associated with naevus of Ota and six were spinal. Histologically, these tumours contain fusiform and epithelioid cells with little or no cellular pleomorphism and rare mitoses. Immunohistochemical and ultrastructural findings confirmed the origin of tumour cells as melanocytic. None of the melanocytomas harboured BRAF, NRAS and KIT mutations. Patients with complete resection had no tumour recurrence. Moreover, patients with incomplete tumour resection followed by radiotherapy showed a higher local control (LC) rate than incomplete resection alone (P < 0·05).

CONCLUSIONS

BRAF, NRAS and KIT mutations appear to be rare, if not completely absent in melanocytomas of the CNS. The complete resection of the tumour or incomplete resection followed by radiotherapy should be considered as better therapeutic options to reduce the tumour recurrence.

Melanocytic Ophthalmic Neoplasms of the Domestic Veterinary Species: A Review

Melanocytic neoplasms in veterinary species occur in various ophthalmic locations including the eyelid, conjunctiva, cornea, sclera, anterior and posterior uvea, and orbit. Histology usually provides the definitive diagnosis for melanocytic ocular neoplasias. The degree of tissue invasiveness and anaplastic cellular characteristics are more reliable indicators of biological behavior than is mitotic index in most ophthalmic melanocytic tumors. Melanocytic neoplasias of the eyelid are predominantly benign in canines and equines, though in felines, there is the potential for metastasis, especially if the conjunctiva is involved. Limbal melanocytic tumors are predominantly benign in all the studied species, though there is a bimodal occurrence with this tumor type in canines, where those that appear in dogs younger than 4 years tended toward active growth, whereas those that appear in dogs older than 8 years tended to progress more slowly, and may not require therapy. The most common location for melanocytic ocular neoplasias in both canines and felines is the anterior uvea. Feline diffuse iris melanoma in particular has a higher incidence of metastasis than does canine nodular anterior uveal melanocytoma. In contrast, posterior uveal melanocytic tumors are rare in both canine and feline species and are considered benign. Orbital melanoma is rare in both canine and feline species; however, it generally carries a grave prognosis owing to its malignant nature. Knowledge of the general biological behavior and its variability among locations within the eye and between species is essential in therapeutic planning.

Orbital melanocytoma completely resected with conservative surgery in association with ipsilateral nevus of Ota: report of a case and review of the literature

BACKGROUND

Melanocytomas are rare pigmented primary lesions of the central nervous system arising from melanocytes of leptomeninges. They occur most frequently in the posterior fossa, Meckel's cave, or along the cervical and thoracic spinal cord. Orbital melanocytomas have been rarely reported. Nevus of Ota is a melanocytic lesion that can be associated with cutaneous and meningeal melanocytic neoplasms.

METHODS AND RESULTS

We describe a case of an orbital melanocytoma associated with ipsilateral Nevus of Ota. A 28-year-old man presented with proptosis and an ipsilateral congenital facial melanocytic lesion (Nevus of Ota). After imaging evaluation, a retro-orbital mass was discovered. A needle biopsy was performed and the diagnosis of melanocytoma rendered. The patient underwent complete surgical excision of the lesion.

CONCLUSION

In order to make the correct diagnosis and to choose the appropriate therapy, it is important to be aware of this rare presentation and its association with Nevus of Ota.

Canine melanoma diagnosis: RACK1 as a potential biological marker

Melanoma diagnosis in dogs can be challenging due to the variety of histological appearances of canine melanocytic neoplasms. Markers of malignancy are needed. Receptor for activated C-kinase 1 (RACK1) was found to characterize melanomas in other mammals. We investigated the value of RACK1 detection in the classification of 19 cutaneous and 5 mucosal melanocytic neoplasms in dogs. These tumors were categorized as melanocytomas or benign and melanomas or malignant after evaluation of their morphology, mitotic index, and Ki-67 growth fraction. Using immunofluorescence, we confirmed microphthalmia-associated transcription factor (MITF) as a marker of normal and transformed melanocytic cells in dog tissues. All control (n = 10) and tumoral (n = 24) samples stained positively for MITF (34/34, 100%). Whereas RACK1 was not detected in healthy skin melanocytes, melanocytic lesions were all positive for RACK1 signal (24/24, 100%). RACK1 cytoplasmic staining appeared with 2 distinct distribution patterns: strong, diffuse, and homogeneous or granular and heterogeneous. All melanoma samples (13/13, 100%) stained homogeneously for RACK1. All melanocytomas (11/11, 100%) stained heterogeneously for RACK1. Immunohistochemistry was less consistent than immunofluorescence for all labelings in melanocytic lesions, which were often very pigmented. Thus, the fluorescent RACK1-MITF labeling pattern helped to distinguish melanomas from melanocytomas. Furthermore, RACK1 labeling correlated with 2 of 11 morphological features linked to malignancy: cell and nuclear size. These results suggest that RACK1 may be used as a marker in dog melanomas.

Dermal melanocytic tumor with CRTC1-TRIM11 fusion: Report of two additional cases with review of the literature of an emerging entity

"Cutaneous melanocytic tumor with CRTC1-TRIM11 fusion" (CMTCT) is a newly described, potentially novel entity that typically presents as a dermal nodule on the head and neck, extremities, and trunk of adults. Histopathologically, it is reported as a nodular or multinodular tumor composed of epithelioid and spindle cells that are variably immunoreactive for S100-protein, SOX10, and MITF along with more specific melanocytic markers such as MelanA and HMB45. With only 11 cases reported in the English literature so far, the neoplasm appears to behave in a relatively indolent fashion. Nevertheless, in one case, local recurrence and synchronous distant metastasis were evident after 13 years. Additional cases with longer follow-up are essential to determine the neoplasm's biologic behavior with more accuracy. Herein, two cases of CMTCT, one arising on the lower back of a 65-year-old female and the other on the arm of a 33-year-old female in addition to a comprehensive literature review are reported.

Melanocytoma of the optic nerve head - a diagnostic dilemma

The clinical features, autofluorescence, B-scan ultrasonography, optical coherence tomography and fluorescein angiography of the lesion were described. Multiple investigation modalities are needed to confirm the benign nature of the lesion. Careful evaluation and follow-up is crucial to avoid misdiagnosis and erroneous management.

Melanocytoma of the optic disk: A review

Melanocytoma is a deeply pigmented variant of melanocytic nevus that classically occurs in the optic disk, sometimes with contiguous involvement of the adjacent retina or choroid. Historically, this tumor was often confused with malignant melanoma both clinically and histopathologically. Today, however, it is generally recognized by its typical clinical features that differ from most melanomas and erroneous enucleation is rarely done. Histopathologically, melanocytoma is composed of intensely pigmented round to oval nevus cells with benign features. Although traditionally believed to be a relatively stationary lesion, it is now known to exhibit minor enlargement in 10--15% of cases and can cause minor visual loss by a variety of mechanisms. In rare instance, it can induce severe visual loss due to spontaneous necrosis of the lesion or compressive optic neuropathy. More importantly, it can exhibit malignant transformation into melanoma in 1--2% of cases. Ophthalmologists should be familiar with melanocytoma of the optic disk and affected patients should be followed periodically.

Is it a primary or metastatic melanocytic neoplasm of the central nervous system?: A molecular based approach

Primary melanocytic neoplasms of the central nervous system (CNS) are uncommon and must be distinguished from metastatic lesions as patients with metastatic disease carry a worse prognosis. Therefore, tools to aid in the diagnosis of a primary CNS melanocytic neoplasm would be of clinical utility. Primary CNS melanocytic neoplasms, including uveal melanomas have frequent mutations in GNAQ and GNA11, but are rare in cutaneous and mucosal melanomas. Additionally, primary uveal melanomas often exhibit monosomy 3 conferring an elevated risk of metastasis. We present a 63 year-old male with a melanocytic neoplasm in the thoracic spinal cord. Molecular studies revealed the tumor contained a GNAQ mutation and four-color fluorescent in situ hybridization (FISH) composed of chromosome enumeration probes for 3, 7, 17 and a locus specific probe for 9p21/CDKN2A yielded a normal result (i.e. two copies per cell), favoring a primary versus metastatic melanocytic neoplasm of the CNS. We report a case in which the combination of mutational analysis and FISH aided in identifying the origin of the neoplasm.

Clinical imaging and high-resolution ultrasonography in melanocytoma management

Purpose:

To demonstrate the utility of high resolution 20 MHz ophthalmic ultrasound in serial follow-up of optic nerve head melanocytoma patients.

Methods:

This study is a retrospective review of 30 patients with melanocytoma of the optic nerve head studied with echography. All patients were evaluated with standard ophthalmic A-scan and B-scan ultrasonography and 10 (33%) underwent high-resolution ultrasound.

Results:

Sixty-two percent (62%) of patients had dome-shaped lesions on ultrasound, twenty-eight percent (28%) presented with mild elevations. The maximum elevation of any lesion was 2.6 mm. The vast majority (89%) of lesions had medium or high internal reflectivity and 89% demonstrated avascularity. Mean follow-up for all patients was nearly 7 years. High-resolution ultrasound enabled enhanced accuracy for detection of lesion dimensions and documentation of growth and possible malignant transformation.

Conclusions:

In this study, we demonstrate a new and important role for the use of ultrasound in this disease as a complementary tool in identifying and following patients with high-risk growth characteristics. These tumor characteristics can be accurately detected with 10 MHz ultrasound in conjunction with standardized A-scan and better differentiated with the 20 MHz technology. Use of these modalities can aid in distinguishing the melanocytomas that grow from choroidal melanomas and can prevent unnecessary treatments.

Autofluorescence imaging in the differential diagnosis of optic disc melanocytoma

PURPOSE

Optic disc melanocytoma (ODM) is a benign tumour that usually occurs on or adjacent to the optic nerve head. The aim of the study was to evaluate fundus autofluorescence (FAF) imaging as a diagnostic tool in ODM.

METHODS

Retrospective comparative case series study of six patients with ODM and a comparing group of four patients with juxtapapillary choroidal nevus (JCN) and four with juxtapapillary uveal melanoma (JUM). Clinical examination was supplemented with ultrasound B-scan examination and spectral-domain optical coherence tomography. FAF images were obtained with the 532-nm laser (Optomap P200Tx) from all patients.

RESULTS

Clinical examination in the ODM group revealed a dome-shaped, darkly pigmented tumour on or adjacent to the optic disc in all patients, with a mean tumour basal dimension 1.4 mm and mean tumour thickness by ultrasonography of 1.0 mm. FAF revealed a totally hypofluorescent mass with sharply demarcated, feathery edges. No hyperfluorescent changes due to orange pigment or subretinal fluid were seen. In contrast, patients with JCN and JUM manifested focal hyperfluorescence as well as larger hyperfluorescent areas at the tumour and its borders.

CONCLUSION

Fundus autofluorescence imaging is a non-invasive adjuvant tool in the differential diagnosis of ODM characterized by lack of hyperfluorescence compared to JCN and JUM.

Malignant Transformation of Optic Nerve Melanocytoma into Melanoma Associated with Ocular Ischemic Syndrome and Oculocardiac Reflex: Case Report and Review of the Literature

PURPOSE

To describe the clinical and pathological features of malignant transformation of an optic nerve melanocytoma over 25 years, associated with spontaneous extensive tumor necrosis, neovascular glaucoma, ocular ischemic syndrome, and oculocardiac reflex.

PROCEDURES

A 60-year-old Caucasian female presented with acute severe left ocular pain and glaucoma with an intraocular pressure of 80 mmHg and bradycardia (28-40 beats/min).

RESULTS

Histopathological examination of the enucleated eye showed features of malignant transformation of a spontaneously necrotic optic nerve melanocytoma associated with ocular ischemic syndrome and neovascular glaucoma.

CONCLUSIONS

Yearly follow-up and awareness of possible but well-documented malignant transformation, even over several decades, is recommended. This case presents malignant transformation of an optic nerve melanocytoma associated with the common complications described in the literature over the years. Of particular interest was the development of oculocardiac reflex in this patient.

The Use of Oncept Melanoma Vaccine in Veterinary Patients: A Review of the Literature

The Oncept melanoma vaccine is xenogeneic DNA vaccine targeting tyrosinase. It is USDA approved for treatment of stage II to III canine oral melanoma and is also used off-label for melanomas arising in other locations and in other species. While the vaccine appears safe, the published data is mixed as to whether it provides a survival benefit, and the use of the vaccine is somewhat controversial in the veterinary oncology community. In this paper, the published literature describing the use of Oncept is reviewed and evaluated.

Primary malignant melanoma of the pleura with rapid progression: A case report and literature review

A primary melanocytic lesion arising from the pleura is a rare occurrence. This is the case report of a 36-year-old female patient with a primary pleural melanocytic tumor. The positron emission tomography/computed tomography scan revealed multiple nodular soft tissue thickenings of the left hemipleura and a large amount of pleural effusion in the left hemithorax. The results of the histological examination confirmed the diagnosis of melanoma. The disease progressed 4 months following immunotherapy and chemotherapy and the patient succumbed to the disease 2 months later. This type of tumor appears to exhibit a highly aggressive biological behavior and responds poorly to immunotherapy and chemotherapy, which are characteristics similar to those exhibited by melanomas arising in other regions.

Intramedullary Melanocytoma of the Cervicothoracic Cord: Case Report and Review of Literature

Melanocytoma is rare pigmented tumor of the leptomeninges which arise from the neural crest. Intramedullary location of the tumor is extremely rare, and only a few case reports are available in the literature. We report a case of 35-year-old female with the entity who had a near total removal of the intramedullary tumor with good postoperative outcome. The available literature is reviewed.

Congenital uveal melanoma?

A 3-month-old infant with a white mother and Asian father presented with discoloration and prominence of the left eye since birth. Examination revealed a normal right eye. The left eye had hyperchromic heterochromia and an enlarged cornea (diameter, 13.0 mm) with intraocular pressure of 26 mm Hg. There were multiple areas of subconjunctival nodular pigmentation that extended posteriorly into the superior fornix. Fundus examination showed a large ciliochoroidal pigmented mass extending from 10:30 to 3:00 o'clock position involving the superior half of the choroid and adjacent ciliary body. The eye was enucleated, confirming the diagnosis of diffuse uveal melanoma with extraocular extension. Systemic surveillance (hepatic panel and ultrasonography of the liver) performed every 6 months for 5 years was has been negative for metastases. The tumor was investigated intensively for the panel of genes (BAP1, BRAF, NRAS12, NRAS61, GNAQ, Kit 9,11,13,17,18) implicated in pathogenesis of blue nevus, cutaneous melanoma, and mucosal melanomas with negative results. Moreover, germline BAP1 mutation could not be identified. This case possibly represents as yet unidentified uveal melanocytic proliferation rather than a true variant of uveal melanoma.

Intramedullary melanocytoma of thoracic spine: A rare case report

Melanocytomas are present in leptomeninges and arise from neural crest during early embryonic development. They are a rare entity and usually occur in the thoracic spine and infratentorial region. We report a 32-year-old female with meningeal melanocytoma of D9-10. Magnetic resonance imaging revealed an intramedullary spinal tumor at D9-D10. Intraoperatively, the tumor was greyish-black in color with moderate vascularity, and was adherent to the cord. The clinical differential diagnoses included cavernoma and melanocytoma. On microscopic examination, the lesion showed sheets of cells with marked pigment deposition, which was obscuring the cellular morphology. The pigment was confirmed to be melanin by Masson's Fontana stain. Immunohistochemistry was performed, which showed positivity for HMB-45, S-100, Vimentin and Melan-A. The cells were negative for cytokeratin, epithelial membrane antigen, Glial fibrillary acidic protein and neuron-specific enolase. Mib-1 labeling index was less than 1%. In view of the lack of nuclear atypia, mitoses, necrosis and low Mib-1-labeling index along with immunohistochemistry profile, the diagnosis of Melanocytoma was made. Melanocytomas are rare pigmented tumors of the spinal cord and posterior cranial fossa. They are benign in nature, but can also be locally aggressive. Melanocytic lesions of the nervous system are to be differentiated from metastatic melanomas and also tumors showing melanin pigment deposition like schwanomma, paraganglioma, medulloblastoma and various gliomas.

Cutaneous melanocytic tumor with CRTC1::TRIM11 fusion and prominent epidermal involvement: A case report

Cutaneous melanocytic tumor with CRTC1::TRIM11 fusion (CMCT) is a recently described entity with only 13 cases reported in the literature. Histopathologically, the neoplasm consists of atypical epithelioid to spindled cells that form a well-circumscribed nodule confined to the dermis and subcutis with cytological features including large vesicular nuclei with prominent nucleoli and abundant eosinophilic cytoplasm. Immunohistochemistry shows variable expressivity of melanocytic markers. Currently, there is limited data regarding long-term outcomes of this newly described entity. Most cases have done well, but there is one case reported with an adverse event. Hence, further studies are needed to accurately classify this tumor. Definitive diagnosis is made by laboratory evidence of CRTC1::TRIM11 fusion. Herein, we report the first case of CMCT with epidermal involvement in the youngest patient known to be affected to date.

Intraventricular melanocytoma diagnosis confirmed by gene mutation profile

Primary leptomeningeal melanocytic tumors (PLMTs) are rare. They usually arise along the spinal cord and at the skull base. Here we report on a patient with a very rare intraventricular melanocytoma. Histologically, a melanocytic tumor was clearly diagnosed. However, to make the uncommon diagnosis of an intraventricular melanocytoma, metastatic melanoma needed to be excluded. Next generation sequencing covering gene mutations that may occur in PLMTs and cutaneous melanoma was performed. The unique gene mutation profile detected, consisting of an activating CYSLTR2 L129Q mutation and EIF1AX G9R mutation and a lack of mutations in genes known to occur in metastatic melanoma (i.e. BRAF or NRAS) confirmed the diagnosis of an intraventricular melanocytoma. This case report is the second intraventricular melanocytoma published to date and demonstrates the value of applying novel genetic assays to make this diagnosis.

Melanocytic naevi, melanocytomas and emerging concepts

With the elucidation of the genetics of melanocytic tumours, new concepts have emerged. An important one is the identification of 'intermediate' melanocytic tumours, those with genetic progression events beyond those of melanocytic naevi but that are not fully malignant. Thus, melanocytic tumours exist on a genetic spectrum that likely corresponds to biological behaviour. There are multiple pathways to melanoma development with different initiating events and characteristic benign melanocytic neoplasms and the precise placement of tumours on these pathways remains to be established and the corresponding risks of progression quantified. In this review, I discuss the classification of melanocytic naevi based on clinical, histopathological and genetic features, as well as the concept of melanocytomas with discussion of specific recognisable subtypes.

Infrared autofluorescence, short-wave autofluorescence and spectral-domain optical coherence tomography of optic disk melanocytomas

AIM

To investigate the findings of infrared fundus autofluorescence (IR-AF) and spectral-domain optical coherence tomography (SD-OCT) in eyes with optic disc melanocytoma (ODM).

METHODS

IR-AF findings and those of other ophthalmologic imaging examinations, including short-wave autofluorescence (SW-AF), fluorescein angiography (FA), fundus color photography, and SD-OCT of 8 eyes of 8 consecutive cases with ODM were assessed.

RESULTS

The ODMs in all cases (100%) presented similar IR-AF, SW-AF, and FA findings. On IR-AF images, ODMs showed outstanding hyper-AF with well-defined outline. On SW-AF images, the area of ODMs presented as hypo-AF. FA images revealed the leaking retinal telangiectasia on the surface of the ODMs. On SD-OCT images in 8 cases (100%), the ODMs were sloped with highly reflective surface, which were disorganized retina and optic nerve layers. In 7 cases (87.5%), peripapillary choroids were involved. The melanocytomas of 8 cases (100%) presented as optically empty spaces. Vitreous seeds were found in one case (12.5%).

CONCLUSION

IR-AF imaging may provide a new modality to evaluate the pathologic features of ODMs, and together with SW-AF imaging, offers a new tool to study biological characteristics associated with ODMs. SD-OCT is a valuable tool in delimitating the tumor extension and providing morphological information about the adjacent retinal tissue.

Melanocytoma of the ciliary body misdiagnosed as iridodialysis

A 62-year-old female presented to our institution with dimness of vision in her right eye. On examination, her best corrected visual acuity was 20/100 in the right eye. The intraocular pressures were 14 mmHg in both eyes. Slit-lamp examination revealed nuclear sclerotic cataracts bilaterally and iridodialysis in her right eye. Seven days after the first visit, cataract surgery was performed without any complications. One year later, she presented to our institution with acute visual loss and ocular pain in the right eye. Best corrected visual acuity of the right eye was light perception and the intraocular pressure was 44 mmHg. Slit-lamp examination revealed a ciliary body mass with widespread pigment dispersion in the anterior segment. Due to no useful vision and uncontrolled pain, enucleation of the right eye was performed. Histopathologic examination revealed a melanocytoma of the ciliary body.

Choroidal melanocytic tumors in dogs: A retrospective study

OBJECTIVE

To describe clinical features of dogs diagnosed with choroidal melanocytic tumors at a veterinary teaching hospital.

ANIMALS STUDIED

Retrospective case series of 13 dogs (14 melanocytic tumors) with choroidal melanocytic tumors.

PROCEDURES

Medical records of dogs evaluated by the Cornell University ophthalmology service with a clinical diagnosis of a choroidal melanocytic tumor between 2008 and 2020 were reviewed. A choroidal melanocytic tumor was clinically defined as any well-demarcated, raised pigmented choroidal lesion underlying the retina. Histopathology results were consulted when available. Signalment and clinical features were recorded, including fundoscopic location, histopathologic findings, treatment, and outcome.

RESULTS

Choroidal melanocytic tumors were identified in 14 eyes of 13 dogs. The mean (±standard deviation) of dogs was 8.6 (±3.5) years. Seven different breeds were represented, with Labrador/Labrador mix being the most common. Ten of the 14 melanocytic tumors were diagnosed incidentally. Four dogs presented for vision loss and ocular discomfort, and diagnosis was made on histopathology examination following enucleation. Pulmonary metastasis was suspected in one dog with an incidentally found choroidal melanocytic tumor OD. Fundoscopic location was available for 8 melanocytic tumors, with 6 (75%) located in the tapetal fundus. Histopathologic diagnosis was melanocytoma for 3 and malignant melanoma in 1 globe, with optic nerve head invasion in 50%. Local recurrence was not seen in any orbit following enucleation.

CONCLUSION

Choroidal melanocytic tumors are uncommon in dogs. Metastasis appears to be rare and was only suspected in one dog, but intraocular tumor growth can lead to retinal detachment, glaucoma, and necessitate enucleation.