A choroidal nevus is best described as which type of lesion?

C A choroidal nevus is a benign melanocytic proliferation, classically a flat or minimally elevated slate-grey lesion 2 mm thick or less.

Which pair of findings over a choroidal melanocytic lesion is most reassuring for a benign nevus?

A Drusen and a halo are signs of chronicity and strongly favour a benign nevus; their absence is itself counted among the TFSOM risk factors.

In the TFSOM risk factors, what thickness of a choroidal melanocytic lesion counts as high risk?

D The T in TFSOM stands for thickness greater than 2 mm; a typical benign nevus measures 2 mm or less.

Which surface pigment over a choroidal lesion is a TFSOM risk factor for melanoma?

B Orange pigment, which is lipofuscin, is the O of TFSOM and appears as bright hyper-autofluorescence on fundus autofluorescence.

How close to the optic disc must a lesion margin be to count as a TFSOM risk factor?

C The M of TFSOM refers to a lesion margin lying within 3 mm of the optic disc.

Which ultrasonographic feature is included among the TFSOM risk factors for choroidal melanoma?

D Ultrasonographic hollowness is the UH of TFSOM-UHHD, and serial B-scan also measures thickness, where increasing values strongly suggest malignancy.

Which imaging test is the most sensitive way to detect subretinal fluid over a choroidal nevus?

A OCT detects subretinal fluid more sensitively than any other modality, and subretinal fluid is the F of the TFSOM risk factors.

What is the simplest way to prove or exclude growth of a choroidal melanocytic lesion over time?

D Widefield colour photography documents lesion margins and size, and serial images provide the simplest objective comparison for growth.

How should a choroidal melanocytic lesion with three or more TFSOM risk factors be managed?

C Three or more risk factors, or documented growth, mark a high-risk lesion carrying a substantial risk of growth into melanoma and require prompt ocular oncology referral.

Which treatment is used for a confirmed small choroidal melanoma?

B Confirmed small melanomas are treated with plaque brachytherapy or another globe-conserving therapy, and early treatment carries a far better prognosis than thick tumours.

Choroidal Nevus vs Melanoma: TFSOM Risk Factors

A pigmented spot in the choroid is one of the commonest incidental findings in the fundus, and one of the most anxiety-provoking.

Most are benign choroidal nevi that will never cause harm, yet a small number are early melanomas that can metastasize and kill.

The whole clinical skill lies in telling a harmless choroidal nevus from a small melanoma before it grows.

Fortunately, the decision is not a guess: a set of validated risk factors, remembered by the mnemonic TFSOM, turns a vague worry into a structured judgement.

Knowing these features tells you which lesions can be photographed and watched, and which need urgent referral to an ocular oncologist.

What Is a Choroidal Nevus?

A choroidal nevus is a benign proliferation of melanocytes in the choroid.

Typical, reassuring features are:

A flat or minimally elevated, slate-grey lesion
Thickness of 2 mm or less
Overlying drusen and a surrounding halo
No subretinal fluid, orange pigment, or symptoms

Drusen and a halo are signs of chronicity and strongly favour a benign nevus.

What Is a Small Choroidal Melanoma?

A small choroidal melanoma is a malignant melanocytic tumour, often indistinguishable from a nevus at a glance.

Worrying features include:

Increasing thickness, usually beyond 2 mm
Subretinal fluid and visual symptoms
Orange pigment (lipofuscin) over the lesion
A margin touching or near the optic disc
Documented growth over time

The more of these features a lesion shows, the more likely it is to be a melanoma rather than a nevus.

Test your knowledge 10 questions from this article

The TFSOM Risk Factors

The risk factors for growth of a small melanocytic lesion are captured by the mnemonic TFSOM-UHHD: “To Find Small Ocular Melanoma – Using Helpful Hints Daily.”

Letter	Risk factor
T	Thickness greater than 2 mm
F	Subretinal Fluid
S	Symptoms (vision loss)
O	Orange pigment
M	Margin within 3 mm of the optic disc
UH	Ultrasonographic Hollowness
H	absence of Halo
D	absence of Drusen

Risk rises with the number of factors: a lesion with none behaves like a nevus, whereas three or more features carry a substantial risk of growth into melanoma.

Diagnostic Evaluation

Multimodal imaging documents the lesion and detects the risk factors objectively.

Ultrasonography

B-scan measures thickness and detects acoustic hollowness
Increasing thickness on serial scans is a powerful sign of malignancy

OCT and Autofluorescence

OCT is the most sensitive way to detect subretinal fluid
Fundus autofluorescence highlights orange pigment as bright hyper-autofluorescence

Photographic Surveillance

Widefield colour photography documents the margins and size for comparison
Serial images are the simplest way to prove or exclude growth

Objective imaging turns a subjective impression into a documented, comparable record.

Differential Diagnosis

Other pigmented or elevated choroidal lesions can enter the differential:

Choroidal melanocytoma — typically jet-black, often juxtapapillary
Congenital hypertrophy of the RPE — flat, well-defined, with lacunae
Choroidal metastasis — often creamy and multifocal
Peripheral exudative haemorrhagic chorioretinopathy — a haemorrhagic peripheral mimic
Congenital or reactive RPE hyperplasia

Applying the TFSOM factors alongside this differential keeps both over- and under-diagnosis in check.

Management

Management follows directly from the risk assessment.

Low-risk nevi (no risk factors) are photographed and reviewed periodically
Intermediate lesions warrant closer follow-up with imaging
High-risk lesions (three or more factors, or documented growth) need prompt referral to an ocular oncology service
Confirmed small melanomas are treated with plaque brachytherapy or other globe-conserving therapy

The safest rule is to refer any lesion whose features or growth raise genuine concern.

Prognosis

Outcomes depend heavily on early recognition.

The vast majority of choroidal nevi remain stable for life
Small melanomas detected and treated early have a far better prognosis than thick tumours
Delay allows growth, metastatic risk, and loss of the eye

In practice, the value of the TFSOM factors is catching the rare dangerous lesion while it is still small and treatable.

References

Shields CL, Shields JA, Kiratli H, et al. “Risk Factors for Growth and Metastasis of Small Choroidal Melanocytic Lesions.” Ophthalmology. 1995;102(9):1351–1361.
Shields CL, Furuta M, Berman EL, et al. “Choroidal Nevus Transformation Into Melanoma: Analysis of 2514 Consecutive Cases.” Archives of Ophthalmology. 2009;127(8):981–987.
Singh AD, Kalyani P, Topham A. “Estimating the Risk of Malignant Transformation of a Choroidal Nevus.” Ophthalmology. 2005;112(10):1784–1789.
Shields CL, Dalvin LA, Yu MD, et al. “Choroidal Nevus Transformation Into Melanoma Per Millimeter Increment in Thickness Using Multimodal Imaging.” Retina. 2019;39(10):1852–1860.
American Academy of Ophthalmology. “Choroidal Nevus.” EyeWiki.

Test yourself

A few questions straight from this article.

1 / 10

Question
A choroidal nevus is best described as which type of lesion?
Tap to reveal

Answer
C

A choroidal nevus is a benign melanocytic proliferation, classically a flat or minimally elevated slate-grey lesion 2 mm thick or less.
Question
Which pair of findings over a choroidal melanocytic lesion is most reassuring for a benign nevus?
Tap to reveal

Answer
A

Drusen and a halo are signs of chronicity and strongly favour a benign nevus; their absence is itself counted among the TFSOM risk factors.
Question
In the TFSOM risk factors, what thickness of a choroidal melanocytic lesion counts as high risk?
Tap to reveal

Answer
D

The T in TFSOM stands for thickness greater than 2 mm; a typical benign nevus measures 2 mm or less.
Question
Which surface pigment over a choroidal lesion is a TFSOM risk factor for melanoma?
Tap to reveal

Answer
B

Orange pigment, which is lipofuscin, is the O of TFSOM and appears as bright hyper-autofluorescence on fundus autofluorescence.
Question
How close to the optic disc must a lesion margin be to count as a TFSOM risk factor?
Tap to reveal

Answer
C

The M of TFSOM refers to a lesion margin lying within 3 mm of the optic disc.
Question
Which ultrasonographic feature is included among the TFSOM risk factors for choroidal melanoma?
Tap to reveal

Answer
D

Ultrasonographic hollowness is the UH of TFSOM-UHHD, and serial B-scan also measures thickness, where increasing values strongly suggest malignancy.
Question
Which imaging test is the most sensitive way to detect subretinal fluid over a choroidal nevus?
Tap to reveal

Answer
A

OCT detects subretinal fluid more sensitively than any other modality, and subretinal fluid is the F of the TFSOM risk factors.
Question
What is the simplest way to prove or exclude growth of a choroidal melanocytic lesion over time?
Tap to reveal

Answer
D

Widefield colour photography documents lesion margins and size, and serial images provide the simplest objective comparison for growth.
Question
How should a choroidal melanocytic lesion with three or more TFSOM risk factors be managed?
Tap to reveal

Answer
C

Three or more risk factors, or documented growth, mark a high-risk lesion carrying a substantial risk of growth into melanoma and require prompt ocular oncology referral.
Question
Which treatment is used for a confirmed small choroidal melanoma?
Tap to reveal

Answer
B

Confirmed small melanomas are treated with plaque brachytherapy or another globe-conserving therapy, and early treatment carries a far better prognosis than thick tumours.

Choroidal Nevus vs Small Melanoma: Applying the TFSOM Risk Factors