By Dr. Marcus Judge

OSCE

During any examination in an OSCE it is important to understand the pathology and reasoning behind each of the signs and symptoms elicited, even if the patient being examined is 'normal'. This article explains how to examine a pigmented skin lesion (a spot or patch of skin that is darker than the skin around it) and the key findings you should look for. It shows you what each sign means and what conditions it may indicate.

The central aim of this examination is to decide whether a pigmented lesion is reassuringly benign or whether it carries features suspicious for malignant melanoma, the most dangerous of the skin cancers. Benign examples are a melanocytic naevus (an ordinary mole) and a seborrhoeic keratosis (a harmless, warty, stuck-on growth). A structured, reproducible approach lets you describe any lesion clearly and apply recognised risk tools such as the ABCDE criteria and the 7-point checklist.

Contents

  1. Introduction
  2. General Inspection
  3. Close Inspection of the Lesion
  4. Palpation
  5. Dermatoscopy
  6. Regional Lymph Node Examination
  7. Completing the Examination
  8. Quiz

Introduction

Wash your hands and don personal protective equipment if appropriate.

Introduce yourself to the patient and ensure to mention your grade e.g. 3rd year medical student/junior doctor/consultant.

Confirm the patient's details taking 3 points of identification, usually the patient's full name, date of birth and NHS or hospital number.

Obtain consent for the examination, ensuring to explain what the examination will entail. Dermatological examination often involves close inspection of the skin and may require the patient to undress, so a clear explanation and a chaperone (an impartial observer present during the examination) are particularly important.

Expose the patient appropriately. Although you will focus on the lesion of concern, malignant skin lesions can be multiple and can arise anywhere. Be prepared to inspect a wide area of skin in good lighting. Ensure the patient is positioned comfortably and that privacy is maintained.

Ask the patient if they have any pain or tenderness before you begin. Also ask whether the lesion itches, bleeds or has changed, as these are important parts of the history that guide your examination.

General Inspection

Begin with a general inspection of the patient from the end of the couch. Note whether they appear well or unwell. Then look for clues that may relate to skin cancer risk, such as evidence of chronic sun exposure (weathered, wrinkled skin and multiple solar lentigines, which are flat brown sun-induced spots), fair skin, red or blond hair and numerous moles. These features are all associated with an increased risk of melanoma.

Scan the visible skin for the overall number, distribution and variety of pigmented lesions. A patient with many naevi (moles) that all look broadly similar is reassuring. A single lesion that stands out as different from all the others is described as the 'ugly duckling' sign. It warrants close attention, as melanomas frequently look unlike a patient's other moles.

The pattern of distribution is itself informative. Lesions concentrated on sun-exposed (photodamaged) sites such as the face, ears, forearms and lower legs reflect cumulative ultraviolet damage. Lentigo maligna melanoma (a melanoma that arises in sun-damaged skin) favours these sites, but melanoma can occur anywhere on the body, not only in areas that get a lot of sun. Strong sun exposure every now and then, such as on holiday, carries more melanoma risk than regular exposure does. Lesions on acral skin (palms, soles and digits) deserve particular care because melanoma here is easily overlooked. In contrast, lesions over the trunk in younger people are the more typical sites for new naevi. Noting where the lesions sit helps you weigh the likelihood of malignancy.

It is also worth noting the patient's skin phototype. Individuals with Fitzpatrick type I or II skin burn easily and tan poorly. They accumulate more ultraviolet-induced DNA damage and are at higher risk of melanoma and non-melanoma skin cancer than those with darker skin.

Look around the bedside for relevant objects such as a wide-brimmed hat, sun cream, dressings over a biopsy site, or a dermatoscope (a handheld magnifying light), which may give clues to the clinical context. Note any obvious scars from previous skin surgery, which may suggest a history of skin cancer. Also note any signs of immunosuppression (a weakened immune system, for example in a transplant patient taking anti-rejection drugs), as immunosuppressed individuals are at markedly increased risk of skin malignancy.

Close Inspection of the Lesion

Move to a close inspection of the lesion of concern. Examine it in good lighting and, where available, with magnification. First record the site and the number of lesions, then describe the lesion systematically. A widely used framework is site, size, shape, colour, morphology and margin, which ensures nothing is omitted.

  • Site: document the anatomical location precisely. Some sites carry particular significance; for example, melanomas on the sole, palm or under a nail (acral lentiginous melanoma) are easily missed and are the most common subtype in people with darker skin. A pigmented band running the length of a nail that extends onto the surrounding skin fold (Hutchinson's sign) raises concern for subungual melanoma (melanoma under the nail) and should never be dismissed as a bruise.
  • Size: measure the lesion in millimetres rather than estimating. A diameter greater than 6 mm is one of the recognised warning features for melanoma, although small melanomas certainly occur.
  • Shape: note whether the lesion is round, oval or irregular. Asymmetry, where one half does not mirror the other, is a concerning feature, as benign naevi tend to be symmetrical.
  • Colour: benign moles are usually a uniform shade of brown. Variation in colour within a single lesion (combinations of brown, black, blue, red, white or grey) reflects melanocytes (the pigment-producing cells) proliferating at different depths and is highly suggestive of melanoma.
  • Morphology: describe whether the lesion is a macule (flat), a papule or nodule (raised), or a plaque. Be aware that elevation alone is not a reliable guide: most early melanomas are flat (superficial spreading type) and most raised pigmented papules are benign moles. It is a new nodular or ulcerated component that is worrying, as nodular melanoma can grow vertically and metastasise early.
  • Margin: benign lesions tend to have a well-defined, regular border. An irregular, notched or poorly defined border suggests uncontrolled growth of malignant cells into surrounding skin.

Try to decide whether the lesion is truly pigmented (melanocytic) or simply thickened, keratotic skin, because several benign lesions can look like melanoma on the ABCDE features described below. The classic mimic is the seborrhoeic keratosis, which has a 'stuck-on' appearance, a greasy or warty surface, and on closer inspection a brain-like (cerebriform) pattern with blackhead-like plugs and tiny pale cysts filled with keratin (the tough protein of the outer skin). Recognising these features should reassure you.

Conversely, a small minority of melanomas are amelanotic, appearing pink or skin-coloured with little or no pigment. These are easily mistaken for a benign lump or even a pyogenic granuloma (a fast-growing, red, easily bleeding nodule), so any persistent, growing or bleeding nodule deserves the same suspicion even when it is not dark.

The most familiar tool for assessing a pigmented lesion is the ABCDE criteria, which formalises many of the features above:

  • A – Asymmetry: the two halves of the lesion are not symmetrical.
  • B – Border: the edge is irregular, blurred or notched.
  • C – Colour: there are two or more colours within the lesion.
  • D – Diameter: the lesion is greater than 6 mm across (the 7-point checklist below uses a slightly different cut-off, 7 mm or more).
  • E – Evolution: the lesion has changed in size, shape, colour or symptoms over time, or is new.

The E for evolution is arguably the single most important feature, because a lesion that is changing is far more concerning than one that has been stable for years. This is why taking a focused history alongside the examination is essential.

Melanoma compared with a benign mole using the ABCD rule SimpleMed

Image - The ABCD features contrasting melanoma (left of each pair) with a benign mole (right): asymmetry, irregular border, colour variation and a diameter greater than 6 mm

Public domain source by the National Cancer Institute [Public domain]

In UK primary care the weighted 7-point checklist is often used to decide whether to refer a lesion under the suspected cancer pathway. Major features (2 points each) are a change in size, an irregular shape and an irregular colour. Minor features (1 point each) are a largest diameter of 7 mm or more, inflammation, oozing and a change in sensation such as itch. A total score of 3 or more prompts a suspected cancer pathway referral (urgent referral to dermatology). NICE also advises the same referral if dermoscopy suggests melanoma, and advises considering it for a lesion that suggests nodular melanoma.

Malignant melanoma pigmented skin lesion SimpleMed

Image - A malignant melanoma showing asymmetry, an irregular notched border and marked variation in colour within a single lesion

Public domain source by the National Cancer Institute [Public domain]

Palpation

Before touching the lesion, don gloves if there is any risk that it is infected. Also wear gloves if you may be exposed to blood or other bodily fluids, for example if the lesion is bleeding or crusted.

Gently palpate the lesion, comparing it to the surrounding normal skin. Assess the following:

  • Surface texture: note whether the lesion feels smooth (as in a benign naevus) or rough and warty. A 'stuck-on', greasy, warty surface is characteristic of a benign seborrhoeic keratosis, a common mimic of melanoma in older patients.
  • Elevation: determine whether the lesion is flat, raised or depressed. A new or growing raised nodule within a previously flat lesion is concerning.
  • Crust: if a crust is present, note whether it lifts to reveal intact or ulcerated skin beneath. A recurrent crust over a pigmented lesion may signal repeated minor bleeding.
  • Temperature: compare the lesion with adjacent skin. Increased warmth points to inflammation or infection rather than an inactive mole.
  • Consistency: describe whether the lesion is soft, firm or hard. A hard, indurated (abnormally firm) lesion is more worrying than a soft one and may reflect dermal invasion (spread into the dermis, the deeper layer of skin).
  • Fluctuance: gently press on opposite edges to test for a fluid-filled centre. Fluctuance suggests a cyst or abscess rather than a solid pigmented tumour.
  • Mobility: assess how freely the lesion moves over the deeper tissues. A lesion that has become tethered or fixed to underlying structures is a worrying sign of invasion, whereas benign lesions usually move with the skin.
  • Tenderness: note any pain on palpation, watching the patient's face. New tenderness in a previously asymptomatic lesion is a change worth documenting.

A related clue is the 'wobble sign', which uses the dermatoscope (the handheld magnifier described under Dermatoscopy below). When the dermatoscope is pushed gently from side to side, a warty-surfaced (papillomatous) intradermal naevus (a mole whose cells lie in the dermis, the deeper layer of skin) wobbles, whereas a seborrhoeic keratosis does not. The sign helps to tell these two benign lesions apart.

Take care to assess whether the lesion bleeds on gentle contact, as spontaneous bleeding or ulceration is a red-flag feature of malignancy. Ulceration reflects loss of the protective epidermis (the outer layer of skin) as the tumour outgrows its blood supply. Under the microscope (on histology), it is an independent marker of poorer prognosis. Always palpate gently to avoid causing discomfort or trauma to a potentially fragile lesion.

Dermatoscopy

A dermatoscope is a handheld device combining magnification with a polarised light source. By reducing surface reflection it allows visualisation of pigment patterns and vascular structures beneath the stratum corneum (the outermost layer of the skin) that are invisible to the naked eye. Used by trained clinicians, dermatoscopy is more accurate than inspection with the naked eye alone for distinguishing benign from malignant pigmented lesions.

In an OSCE you would offer to examine the lesion with a dermatoscope and explain how it works and what you would look for, rather than necessarily performing a full analysis. Reassuring benign patterns include a symmetrical, regular pigment network (an even lattice of brown lines). Features that raise suspicion of melanoma include an atypical (irregular) network, irregular streaks and irregular dots and globules (small dark dots and round clods that vary in size, shape or spread). A blue-white veil (a milky blue-grey haze over part of the lesion) and a regression structure (white, scar-like or grey areas where the lesion has partly faded) also raise suspicion. Simple screening tools such as the three-point checklist (asymmetry, atypical network and blue-white structures) help non-experts decide which lesions to refer.

Dermatoscope used to examine pigmented skin lesions SimpleMed

Image - A dermatoscope, which combines magnification with polarised light to reveal subsurface pigment and vascular patterns

Public domain source by Northerncedar [Public domain]

Regional Lymph Node Examination

If you identify a lesion that is suspicious for melanoma, you must examine the regional lymph nodes that drain the affected area. Melanoma classically spreads first via the lymphatics to the nearest nodal basin (the group of lymph nodes that drains that area of skin), so palpable lymphadenopathy (enlarged lymph nodes) in the relevant territory may indicate metastatic disease and significantly alters staging (how far the cancer has spread) and prognosis.

Palpate the lymph node group that drains the site of the lesion, for example:

  • The cervical nodes for lesions on the head, face and neck.
  • The axillary nodes (armpit) for lesions on the arm, upper trunk and breast.
  • The inguinal nodes (groin) for lesions on the leg, lower trunk and perineum (the area between the genitals and the anus).

Note any nodes that are enlarged, hard, fixed or matted, as these features suggest malignant infiltration rather than reactive change. You should also feel along the line between the lesion and its draining nodes for any in-transit or satellite deposits. These are smaller skin or subcutaneous metastases lying along the lymphatic pathway.

The clinical nodal examination is only the bedside step. If melanoma is confirmed and no nodes are palpable, NICE advises considering a sentinel lymph node biopsy when the Breslow thickness (how deep the melanoma has grown, in millimetres) is greater than 1.0 mm, or 0.8 mm to 1.0 mm with other high-risk features such as ulceration. Sentinel lymph node biopsy is not offered for stage IA melanoma. The procedure samples the first node draining the tumour to detect microscopic spread. Mentioning this in an OSCE shows you understand how the examination feeds into staging.

Cervical Lymph Node Levels SimpleMed

Image - The cervical nodal levels. Knowing the drainage territory of a lesion tells you which nodal basin to examine for spread

SimpleMed original

Completing the Examination

Thank the patient and ensure they are comfortable and re-dressed. Wash your hands.

Summarise your findings, describing the lesion using the site, size, shape, colour, morphology and margin framework and stating whether the ABCDE or 7-point checklist features raise concern.

To complete the examination, state that you would:

  • Perform a full skin examination, checking the entire skin surface for any other suspicious lesions, as people who have had one melanoma are at higher risk of a second, separate melanoma (a second invasive melanoma occurs in about 5 to 10 in every 100 people with melanoma).
  • Examine the nails, scalp, hair, soles, palms and mucous membranes, as these less obvious sites can harbour melanomas that are easily overlooked.
  • Take a focused history to judge the risk and any change over time. Ask about the duration and evolution of the lesion, symptoms such as itching or bleeding, sun exposure and sunburn, use of sunbeds, and any personal or family history of skin cancer.
  • Document the lesion with clinical photography and accurate measurement to allow monitoring of change over time. A typical set comprises a locating image showing where the lesion sits on the body, a close-up macro image, and a dermatoscopic image.
  • Take swabs or skin scrapings where infection is suspected, sending them for microbiology (bacterial culture), virology (viral testing) or fungal culture as appropriate.
  • Refer suspicious lesions urgently to dermatology under the suspected cancer pathway (often still called the 2-week-wait pathway), which aims to give a diagnosis or rule out cancer within 28 days.
  • Arrange definitive diagnosis through the specialist skin cancer team, by excision biopsy: the whole lesion is removed with a small (around 2 mm) clear margin. A partial biopsy of a possible melanoma is best avoided, but may be considered when complete excision is not feasible, for example in a large lesion. The specimen is sent for histology (examination under the microscope) including Breslow thickness (how deep the melanoma has grown, in millimetres), the key prognostic measurement that guides any subsequent wide local excision (a second operation that removes a wider margin of normal skin around the biopsy scar).

Quiz

Preview the Pigmented Skin Lesion OSCE Examination quiz

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