Module 13: Nonmelanocytic Lesions -- Vascular Lesions

Vascular lesions are broadly divided into two categories:

Congenital vascular lesions:

• Hemangiomas -- benign vascular proliferations with hyperplasia of blood vessels (e.g., infantile hemangiomas)
• Vascular malformations -- vascular ectasia from progressive dilation of pre-existing vessels (e.g., port-wine stain / nevus flammeus)

Acquired vascular lesions:

Category	Lesion Types
Benign	Cherry angiomas, angiokeratomas, lymphangioma circumscriptum, pyogenic granuloma, targetoid hemosiderotic hemangioma
Malignant	Kaposi sarcoma, cutaneous angiosarcoma

• Lacunae (lagoons): Round to oval or angulated, well-defined areas corresponding histologically to dilated blood-filled vessels in the papillary dermis. The single most important structure in vascular dermoscopy.
• Septae: Fibrous dividers separating individual lacunae; correspond to connective tissue stroma between dilated vessels.
• Whitish veil: An ill-defined structureless area creating a "ground glass" appearance, corresponding to hyperkeratotic and acanthotic epidermis overlying the vascular proliferation.
• Hypopyon sign: Two-tone lacunae showing a transition from dark to light color, representing blood sedimentation (cellular components settling to the bottom, serum rising to top).
• White rail lines: White streaks intersecting a vascular lesion, corresponding to fibrous septae surrounding capillary tufts.
• White collarette: A ring-shaped squamous structure at the periphery of a lesion, corresponding to hyperplastic adnexal epithelium.
• Rainbow-like pattern: Circumscribed structureless areas demonstrating multiple colors similar to a rainbow, correlated histologically with spindle-like cells in bundles interweaving through vascular spaces.

The dermoscopic evaluation of vascular lesions relies on the recognition of:

1. Color of vascular structures
2. Morphology of vascular structures
3. Arrangement of vascular structures
4. Additional clues such as scale, ulceration, and whitish veil

Correct interpretation of these features prevents unnecessary biopsies of benign lesions while detecting patterns that deviate from benign presentations and require biopsy to rule out amelanotic/hypomelanotic malignant tumors such as melanoma or Merkel cell carcinoma.

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Clinical Features

Infantile hemangiomas:

• Appear within the first days to months of life
• Some newborns show a telangiectatic patch as a premonitory sign
• Characterized by rapid growth/proliferation followed by slow involution
• Present as bright red to violaceous papules, plaques, or tumors of varying size

Cherry hemangiomas (cherry angiomas / Campbell de Morgan spots):

• Common cutaneous capillary proliferations in adults
• Small red to violaceous papules
• Commonly found on the trunk
• Increase in number with age

Dermoscopic Features

Both infantile and cherry hemangiomas share similar dermoscopic characteristics.

Lacunae (the archetypal structure):

• Round to oval or angulated, well-defined areas
• Variable in size
• Tightly clustered or scattered throughout the lesion
• Often separated by fibrous septae

Color variation by depth and thrombosis:

Condition	Color	Histologic Correlate
Superficial (papillary dermis involvement)	Bright red	Dilated blood-filled vessels in superficial papillary dermis
Deeper location	Darker, bluish-purple hue	Deeper vessel dilation with overlying tissue filtering
Partial thrombosis	Focal blue-black color	Thrombosed blood within vessels
Complete thrombosis	Jet-black (entire lesion)	Complete thrombosis of all dilated vessels

Clinical pitfall: Hemangiomas with partial thrombosis can acquire a focal blue-black color and clinically resemble melanoma. Fully thrombosed angiomas present with a jet-black color that may be alarming.

Additional vascular structures:

• Isolated dilated vessels
• In small, early lesions: one or more dilated interconnecting thin-walled vascular channels in the dermal papillae
• In older lesions: loss of rete ridges, atrophy of the superficial epidermis, polypoid lesions composed of dilated communicating channels with scant intervening connective tissue

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Clinical Features

• Port-wine stain (PWS) / nevus flammeus is the most common vascular malformation of the skin
• Capillary malformation of post-capillary venules and dermal capillaries in the papillary and reticular dermis
• Blanchable pink to red patches, usually unilateral or segmental in distribution
• Persistent lesions that may become darker, thicker, and eventually nodular over time
• Clinical appearance depends on vessel depth and size:
• Bright red: superficial ectatic vessels
• Fainter pink: smaller and deeper ectatic vessels
• Purplish: larger and deeper vessels

Dermoscopic Features

Two main structures are observed:

1. Red globules -- represent superficial, vertically oriented capillaries within the papillary dermis
2. Red linear vessels -- represent deeper, ectatic horizontal capillaries within the reticular dermis

Clinical Pearl: This dermoscopic distinction has therapeutic implications. Superficial PWS (red globules pattern) are more responsive and amenable to laser treatment compared to deeper PWS (linear vessel pattern).

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Check Your Understanding

What are the key dermoscopic vascular patterns that help classify vascular lesions?

The key patterns include red-blue lacunae (hemangioma), red-blue to dark homogeneous areas (thrombosed hemangioma), comma-shaped vessels (dermal nevi), crown vessels (sebaceous hyperplasia), and red-purple homogeneous color (angiokeratoma with dark lacunae). The specific vascular architecture is the primary tool for differential diagnosis.

Clinical Scenario

A 52-year-old woman presents with a 4 mm red papule on the upper trunk that has been stable for years. Dermoscopy reveals multiple well-demarcated, round to oval red-to-purple structures (lacunae) arranged in clusters and separated by whitish septae. No pigment network, vessels, or other dermoscopic structures are identified outside the lacunae.

What is your diagnosis and key dermoscopic findings?

Cherry angioma (hemangioma)

Red-to-purple lacunae separated by whitish septae are the hallmark dermoscopic pattern of hemangioma. Lacunae correspond histopathologically to widely dilated, thin-walled vascular spaces in the papillary dermis. The whitish septae correspond to the intervening connective tissue stroma between the dilated vessels. In the Prediction without Pigment algorithm, this "clods-only" pattern (red clods without linear vessels) is one of the four benign monomorphous vessel patterns consistent with a benign diagnosis. However, any apparent hemangioma with vessels seen within the red or purple clods should be excised.

Key Takeaways

• Lacunae (well-demarcated round-to-oval red, red-blue, or black structures) are the defining dermoscopic feature of hemangiomas, corresponding to dilated vascular spaces in the dermis.
• Color within lacunae reflects blood oxygenation state: red (oxygenated), dark red-blue (deoxygenated), and black (thrombosed).
• The red-blue-black color combination is characteristic of vascular lesions and helps distinguish them from melanocytic lesions.

Clinical Features

• Acquired benign vascular proliferations from dilation of pre-existing blood vessels
• Solitary or clustered, red to violaceous, nonkeratotic papules (2-10 mm)
• Progress to dark red/blue-colored, more firm lesions with scaly or verrucous surface

Clinical variants:

Variant	Typical Presentation
Solitary	Lower extremities; may occur anywhere
Multiple	Lower extremities; may occur anywhere
Fordyce spots (vulvar/scrotal)	Multiple, red-to-purple, small papules (<5 mm)
Angiokeratoma of Mibelli	Dorsal/lateral fingers and toes in children and teenagers
Angiokeratoma corporis diffusum	Multiple papules in bathing trunk distribution (trunk and buttocks)
Angiokeratoma circumscriptum	Childhood; grouped or confluent papules on trunk, arms, or legs

Clinical mimics: Melanocytic nevi, Spitz nevi, melanoma, pigmented basal cell carcinoma, seborrheic keratoses, dermatofibromas.

Histology: Dilated blood vessels in the papillary dermis with epidermal changes including acanthosis and varying degrees of overlying hyperkeratosis.

Dermoscopic Features

All clinical variants share similar dermoscopic findings due to similar histopathology.

Two most common dermoscopic structures:

1. Dark lacunae -- Color varies from red and purple to maroon and black depending on depth of ectatic blood vessels
2. Whitish veil -- An ill-defined structureless area giving a whitish "ground glass" film appearance; histologically corresponds to the hyperkeratotic and acanthotic epidermis

Diagnostic performance: The combination of dark lacunae plus whitish veil has a sensitivity of 84% and specificity of 99% for angiokeratomas.

Additional dermoscopic structures:

• Peripheral erythema (suggestive of inflammation)
• Hemorrhagic crusts (suggestive of bleeding)

Differentiating Angiokeratoma from Melanoma

Both melanoma and angiokeratoma can share the blue-black sign (combination of blue and black-pigmented areas involving at least 10% of the lesion surface).

Features favoring angiokeratoma over melanoma:

• Clearly identifiable lacunae separated by septae
• No vessels within the lacunae themselves
• Whitish veil (ground glass pattern from hyperkeratosis)

Features raising concern for melanoma:

• Lacunae-like structures that are irregular
• Not clearly separated by septae
• Containing atypical vessels
• Multicomponent pattern with other melanoma-specific structures (shiny white structures, ulceration)

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Clinical Features

• Benign hamartomatous malformation of dilated lymphatic channels or cysts lined by lymphatic endothelial cells
• May be present at birth or develop in first few years of life
• Clusters of small translucent vesicle-like lesions filled with lymphatic fluid ("frogspawn" appearance)
• May also show sero-hematic or hemorrhagic papules due to blood inclusion

Dermoscopic Features

Most common dermoscopic structures:

• Lacunae
• Vascular structures
• White lines
• Scales
• Hypopyon sign

Lacunae color variation by content:

Lacunae Color	Content
White to yellow	Lymphatic fluid
Pink to red	Blood cells present in dilated lymphatic channels
Dark red to violaceous	Partially or completely thrombosed lacunae

The hypopyon sign (two-tone lacunae) -- the key differentiating feature:

• Displays a transition from dark to light color within a single lacuna
• Represents blood sedimentation: cellular components settle at the bottom, serum rises to the top
• Can be used to differentiate LC from hemangiomas when the lesions are clinically indistinguishable

Two dermoscopic patterns of LC:

1. Pattern A: Yellow lacunae separated by pale septae
2. Pattern B (most common): Yellow to pink lacunae with alternating reddish-blue lacunae representative of hematic content

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Check Your Understanding

How does dermoscopy help distinguish a hemangioma from an amelanotic melanoma?

Hemangiomas show well-demarcated red, red-blue, or dark-blue lacunae (round to oval structures) that may resemble a cluster of grapes. Amelanotic melanoma shows polymorphous vessels (dotted, linear-irregular, and milky-red globules), white shiny structures, and often an irregular arrangement. The regular lacunar pattern of hemangioma versus the polymorphous vasculature of melanoma is the critical distinction.

Clinical Features

• Also known as telangiectatic granuloma or lobular capillary hemangioma
• Benign vascular tumor of skin and mucous membranes
• Suggested to result from hyperplastic, neovascular response secondary to angiogenic stimulus (trauma, infection, drug, pregnancy)
• May occur at any age and site; commonly affects hands, face, and oral mucosa of children and young adults
• Solitary, smooth or lobulated, red papule, often with a collarette of scale
• Usually undergoes rapid growth, stabilizing in size (rarely exceeds 1 cm)
• Friable surface prone to profuse bleeding and potentially ulceration

Dermoscopic Features

Structure	Sensitivity	Specificity	Histologic Correlate
Red homogeneous areas	96.7%	37.1%	Numerous proliferating vessels in a myxoid stroma
White collarette	73.8%	90.7%	Hyperplastic adnexal epithelium at the periphery
White rail lines	45.1%	81.4%	Fibrous septae surrounding capillary tufts
Ulceration	--	--	Surface disruption

Additional findings:

• Vascular structures appreciated in 45% of PGs
• 31% are in the form of serpentine vessels

Characteristic combination: A homogeneous red area separated by white rail lines surrounded by a white collarette is highly characteristic of pyogenic granuloma.

Critical caveat: No individual structure is considered an isolated criterion. Histopathological confirmation is always recommended because pyogenic granulomas may mimic amelanotic melanoma.

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Key Takeaways

• Angiokeratomas show lacunae with a dark-red to black surface crust and surrounding whitish veil, corresponding to thrombosed dilated vessels with overlying hyperkeratosis.
• Pyogenic granuloma shows a homogeneous red structureless area with a collarette of scale and white rail lines; vascular morphology helps distinguish it from amelanotic melanoma.
• Kaposi sarcoma displays a multicolored pattern (rainbow pattern) with structureless areas of blue, red, and brown, reflecting the complex vascular and spindle-cell proliferation.

Clinical Scenario

A 44-year-old man presents with a rapidly growing, red, dome-shaped nodule on the right index finger that bleeds easily with minor trauma. The lesion appeared 3 weeks ago after minor injury. Dermoscopy reveals a homogeneous reddish area covering most of the lesion, a peripheral white collarette, and white rail lines dividing the lesion into sections. Ulceration is present on the surface.

What is your diagnosis and key dermoscopic findings?

Pyogenic granuloma (lobular capillary hemangioma)

Red homogeneous areas (96.7% sensitivity) correspond to numerous proliferating vessels in a myxoid stroma. The white collarette (73.8% sensitivity, 90.7% specificity) corresponds to hyperplastic adnexal epithelium at the periphery and is a highly specific feature. White rail lines (45.1% sensitivity, 81.4% specificity) correspond to fibrous septae surrounding capillary tufts. The history of rapid growth and easy bleeding is characteristic. Importantly, pyogenic granuloma must be distinguished from amelanotic nodular melanoma, which can present similarly. If any atypical dermoscopic features are present (irregular vessels, atypical pigmentation), histopathologic examination is mandatory.

Clinical Features

• Malignant angioproliferative neoplasm of lymphatic endothelial cell origin
• Linked to co-infection with human herpes virus 8 (HHV-8) in all cases
• Characterized by angiogenesis, inflammation, and spindle cell proliferation

Four clinical variants:

Variant	Context
Classic	Elderly patients, especially of Mediterranean/Eastern European descent
Endemic (African)	African populations
Epidemic (HIV-AIDS associated)	Immunocompromised HIV-positive patients
Iatrogenic	Immunosuppressed patients (organ transplant recipients)

Dermoscopic Features

There are no specific dermoscopic patterns exclusive to KS, but the most common and suggestive structures include:

1. Blue-red pigmentation -- the most commonly observed dermoscopic finding
2. Rainbow-like pattern -- circumscribed structureless areas demonstrating multiple colors similar to a rainbow

• Histologically correlated to spindle-like cells formed into bundles interweaving through vascular spaces of various sizes and shapes
• Only visualized in papular or nodular KS (not in macular or bullae-like KS)

1. Scaly surface

Important limitation: The rainbow pattern is not specific for KS. It can also be seen in: dermatofibromas, pyogenic granuloma, melanoma, stasis dermatitis, scars, angiomas, lichen planus, and others.

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Clinical Features

• Rare, aggressive neoplasm of endothelial origin with poor prognosis
• Three clinical variants:

1. Classic angiosarcoma (AS) -- face, neck, and scalp
2. Lymphedema-associated angiosarcoma (LAS)
3. Radiation-induced angiosarcoma (RAS)

• Early lesions: ill-defined violaceous to blue-colored spots (deceptively benign-appearing, leading to diagnostic delay)
• Advanced lesions: violaceous nodules that can ulcerate and bleed easily

Dermoscopic Features

The dermoscopic features of angiosarcoma are not completely understood due to its rarity.

Classic angiosarcoma (AS):

• Various color gradations within the tumor -- a characteristic feature that helps differentiate AS from purpura and ecchymosis
• Pink areas: histologically correlate with pleomorphic cells with minimal luminal differentiation
• Dark red to purple areas: represent organizing thrombus, hemorrhage, and/or secondary dilated vascular structures
• "Steam-like areas" -- white central region with increased intensity in color around the lesion periphery
• White lines -- corresponding to fibrous septae between enlarged neoplastic vascular spaces
• Notably LACKS vascular structures under dermoscopy (vessels and lacunae/lagoons), unlike most other vascular lesions
• This absence may be attributed to the indiscriminate proliferation of cancerous cells, precluding the formation of standard vessels
• Additional features: regions of linear or ring-shaped erythema, skin-colored perifollicular areas, whitish veils

Radiation-induced angiosarcoma (RAS):

• Colors of lower intensity compared to classic AS
• More homogeneous pink-white pattern under dermoscopy
• May also show color gradations, white lines, and strengthening of color at the lesion margin

Lymphedema-associated angiosarcoma (LAS):

• Dermoscopic features have not been specifically described to date

Key diagnostic insight: The paradoxical absence of vascular structures (lacunae, typical vessels) is itself a clue to angiosarcoma. While it appears clinically vascular, dermoscopy reveals a homogeneous pattern with mixed colors (whitish, pink, red, bluish, purple) but without the organized lacunar structures expected in benign vascular lesions.

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Key Takeaways

• Nodular melanoma can mimic thrombosed hemangioma; any dark nodule with blue-white veil, irregular vessels, or white shiny structures should be biopsied.
• The key differentiator for vascular lesions is that structures are composed of blood-filled spaces (lacunae) rather than pigment (melanin), which can be confirmed by pressure blanching.
• Subcutaneous vascular lesions may appear entirely blue and structureless, entering the differential for blue nevus and nodular melanoma.

Clinical Features

• Benign vascular malformation of lymphatic origin confined to the dermis
• Classic description: single, small, violaceous, targetoid papule surrounded by a thin pale area and ecchymotic rim
• The surrounding halo may expand into the periphery over time until it disappears spontaneously, leaving only a central papule
• Clinical appearance is often variable, depending on the stage of its cyclical changes
• Histology: biphasic growth pattern with dilated vessels lined by prominent hobnail endothelial cells in the superficial dermis and narrow neoplastic vessels dissecting collagen in deeper parts

Dermoscopic Features

Most common dermoscopic pattern:

• Central red and/or dark lacunae
• Peripheral red-brownish homogeneous area (rim pattern)

Differential diagnosis caveat: This pattern may also be seen in angiokeratomas and thrombosed hemangiomas. Due to the potential for indistinct, nontargetoid, and atypical clinical and dermoscopic presentations, diagnosis should be confirmed by histology to rule out similarly appearing lesions such as amelanotic/hypomelanotic melanoma.

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Key Takeaways

• A systematic approach to vascular lesions starts by identifying lacunae, then assessing color (red, blue, black), surface changes (scale, crust), and associated features (collarette, white veil).
• When a lesion appears entirely vascular but shows atypical features (asymmetry, polymorphous vessels, white structures), biopsy should not be deferred.
• Dermoscopic pressure testing (pressing the dermatoscope to blanch vessels) can help confirm a vascular origin but does not exclude malignancy.

One of the most critical differential diagnoses in dermoscopy is distinguishing benign vascular lesions from amelanotic/hypomelanotic melanoma (particularly nodular melanoma). Several vascular lesions can clinically and dermoscopically mimic melanoma:

Scenario	Key Distinguishing Features
Thrombosed hemangioma vs. melanoma	Hemangioma: well-defined lacunae separated by septae, no vessels within lacunae. Melanoma: irregular lacunae-like structures, atypical vessels, multicomponent pattern
Angiokeratoma vs. melanoma	Angiokeratoma: dark lacunae + whitish veil (sensitivity 84%, specificity 99%). Melanoma: blue-black sign without clear lacunar-septal architecture, shiny white structures, ulceration
Pyogenic granuloma vs. amelanotic melanoma	PG: red homogeneous area + white collarette + white rail lines. Melanoma: polymorphous vessels, irregular pattern. Always confirm PG histologically
Angiosarcoma vs. hemangioma	AS: lacks lacunae/vascular structures, shows color gradations and steam-like areas. Hemangioma: well-defined lacunae with septae
THH vs. melanoma	THH: central lacunae + peripheral homogeneous rim. Always confirm histologically for atypical presentations

General principle: When a clinically vascular-appearing lesion shows dermoscopic features that deviate from recognized benign vascular patterns -- particularly irregular structures, atypical vessels, multicomponent patterns, or shiny white structures -- biopsy is indicated to rule out malignancy.

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