Dermoscopic features of epidermoid cyst beyond punctum
How to cite this article: Behera B, Kumari R, Thappa DM, Gochhait D. Dermoscopic features of epidermoid cyst beyond punctum. Indian J Dermatol Venereol Leprol 2022;88:404-8.
Epidermoid cyst, also called sebaceous cyst, is the most common benign cutaneous cyst encountered during clinical practice. It usually presents as an asymptomatic slow-growing, spherical, smooth, elastic and dome-shaped keratin-filled cyst. Due to variable size, colour, and consistency, it often resembles various benign adnexal and non-adnexal tumours clinically. The dermoscopic examination is primarily aimed at demonstrating the punctum, which facilitates the diagnosis.
All our patients were skin phototypes IV and V. None of them presented with punctum either clinically or dermoscopically. Table 1 lists the clinical and dermoscopic (Heine Delta 20, under non-polarised mode) details of our patients [Figures 1–7]. Each diagnosis was confirmed by histopathology. Neither patient showed any feature of rupture, secondary bacterial infection, or calcification. All lesions were successfully excised without any recurrence.
|Cases||Age/gender||Location||Morphology||Differential diagnosis||Dermoscopic features|
|1||16/M||Chin||Yellowish nodule with telangiectasia||Non-Langerhans histiocytosis||Yellowish-white homogeneous area with arborising vessels|
|2||46/M||Lower back||Macro comedone||Dilated pore of Winer Pilar sheath acanthoma||Brown keratotic plug surrounded by bluish-white homogeneous area|
|3||24/M||Shoulder||Bluish cyst with telangiectasia||Sebaceous cyst Hidrocystoma||White homogeneous area with arborising vessels|
|4||40/M||Abdomen||Light blue firm nodule||Sebaceous cyst||Bluish-white homogeneous area|
|5||60/F||Arm||Hyperpigmented keratotic papule||Keratoacanthoma||Central brown-black keratotic area surrounded by bluish-white homogeneous area|
|6||45/F||Elbow||Skin-coloured cyst Sebaceous cyst||Phaeohyphomycosis||Skin coloured to white homogeneous area
Focal hairpin vessels
Peripheral ridge and groove area
|7||50/M||Abdomen||Reddish-brown nodule||Aneurysmal or haemosiderotic
|Grey-to-grey-white homogeneous area
Pigment network and rings
Linear irregular crypts
Diagnosis of epidermoid cyst is essentially clinical. A cystic consistency with central punctum is usually diagnostic. However, diagnostic dilemma arises when the cystic consistency becomes firm or hard with or without tenderness which may be secondary to bacterial infection, inflammation, and calcification. Additionally, lack of punctum and colour variation, especially in darker skin, may result in misdiagnosis.
In this series, the clinical differentials were diverse due to following reasons: morphological variation ranging from cyst, nodule, open macro-comedone to keratotic papule and heterogeneous colour such as skin coloured, yellow and blue to reddish-brown.
Dermoscopic examination is a useful supplementary tool in diagnosing various cutaneous cysts and tumours. In epidermoid cysts, demonstration of a punctum, called the pore sign, facilitates the diagnosis.1 Other features include white, yellow, and blue homogeneous areas and arborizing vessels.2-4 Dermoscopy revealed the punctum in almost 60% cases, even when clinically invisible.1 In our experience, the pore sign helps in differentiating facial and scalp epidermoid cysts from trichilemmal cyst, another common cystic lesion. Likewise, in acral areas, the pore sign helps in ruling out phaeohyphomycosis and myxoid cyst. A recent study reported that pore sign, blue-white veil and arborizing vessels were associated with unruptured epidermoid cyst while red lacunae and peripheral branched linear vessels indicated ruptured epidermoid cysts.5
In the present series, we included patients who did not reveal any punctum, either clinically or dermoscopically. We observed seven dermoscopic patterns, which are mentioned in Table 2 along with relevant differential diagnoses.
|Patterns||Dermoscopic features||Dermoscopic differentials|
|Pattern 1||Yellow-white homogeneous area with arborising vessels||• Non-Langerhans cell histiocytosis|
|Pattern 2||Brown keratotic plug surrounded by bluish-white homogeneous area||• Dilated pore of Winer|
|Pattern 3||White homogeneous area and arborising vessels||• Non-pigmented basal cell carcinoma|
|• Solitary apocrine hidrocystoma|
|Pattern 4||Bluish-white homogenous area||• Chondroid syringoma|
|• Solitary apocrine hidrocystoma|
|Pattern 5||Central brown-black keratotic area surrounded by bluish-white homogeneous area||• Keratoacanthoma|
|Pattern 6||Skin coloured to white homogeneous area||• Neurofibroma|
|Pattern 7||Grey-to-grey-white homogeneous area with linear irregular crypts||• Neurofibroma|
The white homogeneous areas represent keratin, the yellow colour results from mass effect of concentric layers of laminated keratin, brown homogeneous areas occur due to increase epidermal melanin and the bluish colour may be attributed to Tyndall effect, as described in apocrine hidrocystoma.
In conclusion, we describe some diverse and unreported dermoscopic features of epidermoid cysts without punctum, in seven patients with skin of colour. Additionally, grey homogeneous areas, pigment networks and rings may be observed in such patients. Thus, an epidermoid cyst without dermoscopic pore sign may mimic various appendageal tumours, and a pathological examination is necessary for accurate diagnosis.
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Conflicts of interest
There are no conflicts of interest.