Vascular Lesions



Vascular Lesions


Daniel D. Miller

Alejandro A. Gru

Sheilagh M. Maguiness



Introduction and Classification

The field of vascular anomalies has grown at a rapid pace over the past decade. The International Society for the Study of Vascular Anomalies (ISSVA) was first established in 1976 by Drs John Mulliken and Anthony Young. Since then, ISSVA has developed and updated the classification schema for vascular lesions, building from the initial biologic classification proposed by Mulliken and Glowacki in 1982.1 The most recent classification for vascular anomalies was proposed in 20142 (Table 25-1). Genetic advances have led to an improved understanding of these conditions and paved the way for potential targeted therapies. Correct classification of vascular anomalies is of utmost importance, because although the lesions may clinically resemble one another, the prognosis and natural history of this heterogeneous group of conditions varies widely. Accurate and precise diagnosis is necessary and possible on the basis of the clinical appearance, natural history, imaging, and histopathologic features of the malformation or tumor. This chapter reviews the basic epidemiology, etiology, clinical manifestations, and histopathology for the most common pediatric vascular tumors and malformations.

Vascular tumors comprise a heterogeneous group of vascular lesions, many of which most commonly present during childhood. Table 25-2 lists the ISSVA basic classification of vascular tumors, of which infantile hemangioma is the most common, classic, pediatric vascular tumor.


INFANTILE HEMANGIOMA


Definition and Epidemiology

Infantile hemangiomas (IH) are present in about 4% of newborns.3 They are an extremely common type of vascular tumor that have a distinctive natural history.


Etiology

Risk factors for the development of IH are well characterized and include female gender, low birth weight, and Caucasian skin type. The etiology of IH remains incompletely understood; however, experts believe that a somatic mutation may be responsible.


Clinical Presentation

IH are typically not present at birth. Rather, they may exist initially as a premonitory mark/precursor lesion, such as an
area of pallor or telangiectasia; initially, they may resemble a bruise. Hemangiomas may occur anywhere on the body but may have a predilection for the head and neck. Hemangiomas grow rapidly over the first 5 to 7 weeks of life, ultimately growth stabilizes, and IH involute or regress slowly over the course of years.4 There are several clinical subtypes, including superficial, deep, mixed, and IH with minimal or arrested growth. All have a typical clinical appearance in the skin. Superficial IH are well-demarcated bright red vascular plaques. Deep IH are bluish-hued subcutaneous nodules. Mixed IH demonstrate both a red superficial component and a deeper underlying bluish tumor. IH with minimal or arrested growth tend to favor the lower body and are often flat or telangiectatic in their appearance, with proliferation occurring only in <20% of the lesion, most often at the periphery (Figure 25-1A-D clinical subtypes). IH may be solitary or multifocal in their presentation. When they appear to occupy a region or territory of the body, for example large facial hemangiomas on the frontotemporal area, they may be associated with underlying structural anomalies as seen in Posterior fossa anomalies, large facial Hemangioma, Arterial anomalies, Cardiac anomalies, Eye anomalies (PHACE).5








TABLE 25-1. Classification of vascular anomalies: basic overview2 (ISSVA, 2014)











Vascular Tumors


Vascular Malformations


Benign


Locally aggressive/Borderline


Malignant


Simple: CM, VM, LM, AVM, AVF (Table 25-3)


Combined: See Table 25-4


Associated with other anomalies: See Table 25-5


Abbreviations: AVF, arteriovenous fistulae; AVM, arteriovenous malformations; CM, capillary malformations; ISSVA, International Society for the Study of Vascular Anomalies; LM, lymphatic malformations; VM, venous malformations.









TABLE 25-2. Vascular tumors (ISSVA, 2014)

















Category


Specific Tumors


Benign




  • Infantile hemangioma



  • Congenital hemangiomas (RICH, NICH, PICH)



  • Tufted angioma



  • Spindle cell hemangioma



  • Epithelioid hemangioma



  • Pyogenic granuloma



  • Microvenular hemangioma


Locally Aggressive/Borderline Tumors




  • Kaposiform hemangioendothelioma



  • Retiform hemangioendothelioma



  • PILA, Dabska tumor



  • Composite hemangioendothelioma



  • Pseudomyogenic hemangioendothelioma



  • Kaposi sarcoma



  • Others


Malignant




  • Angiosarcoma



  • Epithelioid hemangioendothelioma



  • Others


Abbreviations: NICH, noninvoluting congenital hemangioma; PICH, partially involuting congenital hemangioma; PILA, papillary intralymphatic angioendothelioma; RICH, rapidly involuting congenital hemangioma.



Histologic Findings

In its proliferative phase, IH exhibits lobules and sheets of capillaries lined by plump endothelial cells arranged in “back-to-back” fashion, with little intervening stroma (Figure 25-2A and B). IH may be centered superficially, deep or both. Occasional mitoses and scattered mast cells may be observed.6,7 In the involutional phase, stromal fibrosis is increased between the vascular lobules. Endothelial cells are typically more flattened, basement membranes thicken, and mitotic activity is diminished. Biopsy of fully involuted IH demonstrates a “fibrofatty” residuum, with thinned epidermis, scar tissue (including loss of cutaneous appendages), and diminished dermal elastic fibers. The sparse remaining vessels appear small and “ghosted” with thickened basement membranes and often occluded lumens.6

The histopathologic differential diagnosis for IH includes congenital hemangiomas (see following paragraphs) and pyogenic granuloma; glucose transporter protein isoform 1 (GLUT1) immunostain readily distinguishes IH from other vascular anomalies, the majority of which exhibit negative staining. GLUT1 facilitates glucose transport across the cell membranes of erythrocytes and is widely expressed in fetal tissue.8 GLUT1 immunostain labels IH endothelial cells in all phases of its evolution.



CONGENITAL HEMANGIOMAS


Definition and Epidemiology

Congenital hemangiomas (CH) are an uncommon but benign type of vascular tumor that present fully formed at birth. They are distinct from IH in many ways, including their natural history and histopathologic features. CH occur much less frequently than IH in only 0.3% of newborns, according to one prospective study.3


Etiology

CH may occur anywhere on the body and have no clear gender predilection. They are typically solitary, although multifocal variants have been reported. Clinical variants of CH include rapidly involuting congenital hemangioma (RICH), noninvoluting congenital hemangioma (NICH), and partially involuting congenital hemangioma (PICH).9 These three subtypes share significant clinical and histopathologic overlap and also genetic etiology. Mutations in GNAQ and GNA11 have been reported in both RICH and NICH.10 Thus, many authors believe that these uncommon vascular tumors exist on a spectrum.







FIGURE 25-1. A, Superficial infantile hemangioma. B, Deep infantile hemangioma. C, Mixed, superficial, and deep infantile hemangioma. D, Infantile hemangioma with minimal or arrested growth.


Clinical Presentation

RICH is likely the most common variant. These tumors present right at birth as solitary, large, violaceous vascular tumors. They may be exophytic and often have a surrounding halo of vasoconstriction (Figure 25-3A). They are high-flow vascular tumors and demonstrate high flow on Doppler evaluation. Usually, they are asymptomatic, although rarely, ulceration, bleeding (much more high flow than an IH), or transient thrombocytopenia may occur. They involute rapidly over the first few months of life, leaving behind atrophic, anetodermalike plaques with prominent veins (Figure 25-3B).

NICH are less common. They typically present as round or oval plaques or nodules with a bluish hue and overlying venules and telangiectasias (Figure 25-4). They also demonstrate a surrounding halo of pallor/vasoconstriction and high blood flow on Doppler evaluation. NICH are generally asymptomatic, although because they persist over time, they may become more symptomatic or bothersome. Pain is sometimes reported, and lesions may expand or worsen during times of hormonal excess such as puberty or pregnancy.11


Histologic Findings

RICH is comprised of small, mostly similar-sized dermal lobules of capillaries. Endothelial cells are plump and surrounded by layers of pericytes. Prominent fibrous tissue is typically present, surrounding individual capillary lobules. Centrally, RICH often has near-absence of these lobules but instead shows dense fibrosis and large, thickened draining veins with irregular muscular walls. Aneurysmally dilated vessels, interstitial hemosiderin, and calcification are also commonly present. Extramedullary hematopoiesis may also be seen6,12 (Figure 25-5A and B).







FIGURE 25-2. Infantile hemangioma (IH). A, Lobulated clusters of small, thin-walled vessels with minimal intervening stroma are present in the dermis (H&E-stained section, 100× magnification). B, Glucose transporter protein isoform 1 immunostain, with a positive labeling of the endothelium of lesional vessels in IH.

NICH exhibits larger, varying sized lobules of capillaries that may coalesce into larger masses (Figure 25-5C). These capillaries are lined by plump endothelial cells with little cytoplasm; some lobules may contain more dilated capillaries lined by hyperchromatic small nuclei that often hobnail into the vascular lumen. Cytoplasmic eosinophilic globules are occasionally present. The main differential diagnosis for RICH and NICH includes IH and pyogenic granuloma. GLUT1 immunostain is highly effective in distinguishing between IH and congenital hemangioma, because the latter is consistently negative.






FIGURE 25-3. Rapidly involuting congenital hemangioma of the left leg (A) at 4 weeks (B) at 11 weeks.








FIGURE 25-4. Noninvoluting congenital hemangioma of the neck.






FIGURE 25-5. Histopathology of congenital hemangiomas. A, Rapidly involuting congenital hemangioma: Similar-sized lobules of capillaries fill and expand the dermis (H&E, 20× magnification). B, Partially involuting congenital hemangioma: Vascular lobules with intervening stromal fibrosis indicative of partial involution (100× magnification). C, Noninvoluting congenital hemangioma: Variably sized capillaries with hyperchromatic, occasionally hobnailing, endothelial cells (40× magnification).


PYOGENIC GRANULOMA (“LOBULAR CAPILLARY HEMANGIOMA”)


Definition and Epidemiology

Pyogenic granuloma (PG) is one of the most commonly acquired vascular tumors in children. It is a benign tumor with a male predilection that can occur at any site on the body at any age, although the vast majority occur in children.


Etiology

Recently, the majority of PGs have been shown to arise secondary to mutations in BRAF, and in a smaller subset, to mutations in RAS.13,14 In the case of the BRAF mutation, this is the same “hotspot” that is present in many human cancers, including melanoma, leading to a constitutive activation of RAS-MAPK signaling in mutated cells. Interestingly, PGs are also known to arise in the setting of treatment with BRAF inhibitors, which may represent a paradoxical activation of MAPK signaling in this setting.15,16







FIGURE 25-6. Pyogenic granuloma on the lower eyelid margin.


Clinical Presentation

Clinically, PG present as bright red, pedunculated papules varying in size from a few millimeters up to several centimeters, often with a surrounding collarette of scale (Figure 25-6). The overlying epidermis is often eroded or ulcerated. Thus, common complications include bleeding and infection. PGs may occur sporadically or arise secondarily. For example, there may be a history of antecedent trauma, such as an insect bite or scratch, hormonal or other factors involved. In addition, PGs are known to occur secondarily within several different types of vascular anomalies, including capillary malformations and arteriovenous malformations (AVMs), which may be directly related to their genetic etiology.17






FIGURE 25-7. Pyogenic granuloma (PG). A, An epidermal collarette is seen surrounding an upper dermal proliferation of small, thin-walled vessels arranged in lobules and separated by thin fibrous septae (H&E-stained section, 40× magnification). B and C, Intravascular PG: clusters of small vessels with a lobulated architecture filling a dilated, thin-walled vessel (20× and 40× magnification, respectively).


Histologic Findings

PG exhibits an exophytic, polypoid tumor predominantly within the upper dermis, often with central shallow ulceration and an adjacent epidermal collarette (Figure 25-7A). Clusters of capillaries and venules are lined by plump endothelial cells and are typically organized into discrete lobules by interlacing strands of fibrotic stroma. Dermal edema and lymphocytes are commonly present, as are neutrophils in cases of ulceration. A larger feeding arterial vessel may be present at the base of the tumor. PG with partial regression
demonstrates increased fibrosis and diminished vascular lobules. Deep dermal or subcutaneous presentations of PG are not uncommon and may be intravascular. Intravascular PG presents within the lumen of a vein or artery. Intravenous PG was originally described by Cooper et al. in 1979,18 as an intraluminal polyp comprised by lobules of capillaries lined by flattened or rounded endothelial cells (Figure 25-7B). A surrounding fibrous stroma is also usually observed.19,20

The primary differential diagnosis for PG in a neonate or infant is a superficially sampled IH. Negative GLUT1 immunostaining will confirm the diagnosis in this situation. Deep PG may resemble other benign vascular tumors such as tufted angioma; the characteristic lymphatic structures in tufted angioma aid in differentiation.



SPINDLE CELL HEMANGIOMA


Definition and Epidemiology

Spindle cell hemangioma (SCH) was originally described as a hemangioendothelioma, implying low-grade malignant potential.21 As it is now understood to have benign biologic behavior, it is classified as a hemangioma.22 SCH is one of the characteristic findings in Mafucci syndrome.






FIGURE 25-8. Spindle cell hemangioma. A, Well-circumscribed tumor with dense cellularity centrally and dilated thin-walled vessels peripherally (20× magnification). B, Sheets of spindled cells that may resemble nodular Kaposi’s sarcoma (200× magnification). Digital slides courtesy of Path Presenter.com.


Etiology

The majority of SCH are known to arise because of mutations in IDH1 or IDH2.23 This mutation is common both to sporadic SCH and those found in Maffucci syndrome. IDH mutations appear to be specific to this vascular tumor and have not been observed in other vascular anomalies.23


Clinical Presentation

SCH presents as red-brown to blue nodules in the dermis or subcutaneous tissue. SCH is often multifocal and occurs most frequently on the distal extremities.24 Lesions are often tender to palpation.


Histopathology

SCH is a tumor seen in both the dermis and the subcutis, which exhibits an admixture of thin-walled dilated venous channels, and nodules of spindled cells with extravasated erythrocytes, which resemble nodular Kaposi’s sarcoma (KS)21,22 (Figure 25-8). Microthrombi with organization may be seen within venous channels. A subpopulation of ovoid cells with readily visible cytoplasmic vacuoles may also be seen. This latter cell population and the presence of venous channels permit distinction from KS, as does negative HHV8 staining. Focal positivity with lymphatic immunostains including D2-40, Prox1, and Wilms tumor-1 (WT-1) in both the vascular structures and spindle cell population suggests a lymphatic origin.25




EPITHELIOID HEMANGIOMA


Definition and Epidemiology

Epithelioid hemangioma (EH) is a rare vascular tumor with highly variable histomorphology. Nonetheless, it is a distinctive vascular neoplasm displaying well-formed vascular channels lined by prominent epithelioid endothelial cells.26

EH has previously been described under numerous designations, including angiolymphoid hyperplasia with eosinophilia (ALHE), intravenous atypical vascular tumor, inflammatory angiomatous nodule, and histiocytoid hemangioma.27 In the past, this tumor was believed to arise primarily in the skin of the head and neck. However, it is now recognized that EH may occur anywhere on the body in any tissue or organ, particularly in the bone.28 Bony EH may lead to significant destruction, and thus, it is important to distinguish it from malignant vascular tumors or other neoplasms.


Etiology

Recently, FOS gene rearrangements have been observed in nearly one-third of EH in a variety of anatomic locations and histologic variants. Of note, bony EHs tended to harbor this rearrangement most frequently, whereas very few of the cutaneous ALHE-type EHs (ie, the head and neck-predominant variant) demonstrated this change.27






FIGURE 25-9. Epithelioid hemangioma (EH). A and B, Angiolymphoid hyperplasia with eosinophilia-type. Small vessels with epithelioid endothelial cells with vacuolated cytoplasm, and surrounding inflammation rich in eosinophils (100× and 200× magnification). C, Cellular EH variant that may mimic epithelioid hemangioendothelioma or angiosarcoma (200× magnification).


Clinical Presentation

Cutaneous variants of EH present as red-to-blue firm, round nodules or clustered papules that tend to itch; patients may also report a pulsatile sensation. As noted previously, the head and neck regions are the most common cutaneous locations, but EH may present at any anatomic site, including the penis.27


Histologic Findings

Cutaneous EH is typically centered within the dermis, with circumscribed borders and an often lobulated growth pattern. EH is composed of capillaries lined by epithelioid endothelial cells that are occasionally vacuolated (Figure 25-9A and B). These capillaries have patent lumens. The surrounding stroma contains a variably dense inflammatory infiltrate of eosinophils, lymphocytes, and occasionally plasma cells.

The differential diagnosis varies on the basis of EH presentation. ALHE-type lesions may be confused with Kimura disease; the latter tends to exhibit deeper tissue involvement and a predominantly inflammatory pattern (commonly with
lymphoid follicles) and a lesser vascular element. More cellular EH types may mimic malignant tumors such as epithelioid hemangioendothelioma (EHE) or even epithelioid angiosarcoma (AS) (Figure 25-9C). Immunohistochemistry and molecular studies such as fluorescent in situ hybridization (FISH) can be helpful in ruling in these malignant tumors, because 90% of EHE demonstrate a characteristic WWTR1-CAMTA1 fusion, which results from a t(1;3)(p36;q25) translocation,29 and many ASs demonstrate MYC amplification on FISH and/or MYC-positivity on immunohistochemistry.30



MICROVENULAR HEMANGIOMA


Definition and Epidemiology

Microvenular hemangioma is an uncommon, acquired benign vascular tumor; less than 100 cases have been reported in the medical literature. It typically presents as a solitary lesion in adulthood, with a slight female predominance and an average age of onset of 32, but occasionally may be seen in children.31,32 A patient as young as 16 months of age has been reported.31


Etiology

As a sporadic, typically solitary tumor of adult onset, the pathogenesis of microvenular hemangioma is not well understood. A single patient with POEMS syndrome (Polyneuropathy, Organomegaly, Endocrinopathy, Monoclonal protein, Skin changes) presenting with multiple microvenular hemangiomas has been reported33; all other reported patients with multiple lesions have had no identifiable comorbidities.34






FIGURE 25-10. Microvenular hemangioma. A and B, Interstitially arrayed small, thin-walled vessels dissecting between dermal collagen fibers (40× and 100× magnification). Digital slides courtesy of Path Presenter.com.


Clinical Presentation

Microvenular hemangioma presents in most cases as a solitary lesion, most commonly on the trunk or upper extremities, with a reddish brown papule or plaque less than 2 cm in diameter.31 Most are asymptomatic.


Histologic Findings

The characteristic microscopic finding is of many small, thinwalled vessels interstitially arrayed, dissecting between collagen fibers in the mid-dermis (Figure 25-10A and B). Adnexocentricity may present. Endothelial cells are bland in appearance, with a visible surrounding pericyte layer. Surrounding stromal collagen may be mildly sclerotic, and mild lymphoplasmacytic inflammation is often present. Lesional cells uniformly stain with CD31, CD34, and ERG, and are negative on D2-40.31 GLUT1 immunostaining is consistently negative.35



Tufted Angioma and Kaposiform Hemangioendothelioma


Definition and Epidemiology

Tufted angioma (TA) and kaposiform hemangioendothelioma (KHE) are classified according to ISSVA as vascular tumors with benign or aggressive characteristics, respectively. These lesions share many similar clinical and
histopathologic features and thus it is felt that they may exist together on a spectrum. On one end, TAs are considered benign and tend to be smaller in size, whereas KHE is locally aggressive and potentially life threatening. Both may be associated with a consumptive coagulopathy known as Kasabach Merritt phenomenon (KMP), which is the main source of mortality in the setting of KHE. This phenomenon does not occur in the more common entity of IH. KMP occurs because of platelet trapping within the aberrant vessels of these two unique tumors. In extensive, infiltrative lesions, more commonly with KHE, this leads to profound thrombocytopenia, hypofibrinogenemia, elevated D-dimer, and prolonged prothrombin time and activated partial thromboplastin time. Infants with KMP are at risk for life-threatening bleeding/hemorrhage.36






FIGURE 25-11. Tufted angioma on the left upper extremity in a 10-year-old female.






FIGURE 25-12. Tufted angioma. A, Rounded lobules of small, thin-walled vessels in the deep dermis, with minimal intervening stromal changes and absence of subcutaneous extension (H&E-stained section, 40× magnification). B, Crescentic lymphatic channels encircle individual lobules (H&E-stained section, 200× magnification).


TUFTED ANGIOMA


Clinical Presentation

TAs are rare vascular tumors that are usually limited to the skin and subcutis and may occur anywhere on the body. TA tends to grow slowly and is unlikely to be infiltrative. It is usually solitary, and may appear clinically as an indurated, violaceous plaque with overlying hypertrichosis or hyperhidrosis (Figure 25-11). In the case of very extensive lesions, TA may also be associated with KMP; however, this is less common in the setting of TA than in that of KHE. The clinical course for TA is variable; some lesions may regress spontaneously, whereas others persist.


Histologic Findings

TA exhibits well-defined lobules of closely apposed capillaries within the dermis and upper subcutis. Given their notably round, blue appearance at scanning magnification, these lobules are colloquially referred to as “cannonballs” (Figure 25-12A and B). Endothelial cells are often subtly spindled.37 Individual lobules exhibit a surrounding thin, crescentic lymphatic channel, which labels positively with lymphatic marker immunostains such as D2-40 and PROX-1. Spindled endothelial cells may demonstrate similar positivity, although most of the central portions of lobules are D2-40 negative.38


The primary differential diagnosis is KHE. KHE and TA exhibit many overlapping features; in addition to the abovementioned findings, both may also exhibit microthrombi, hemosiderin-laden endothelial cells, extravasated red blood cells, and a lymphatic immunoprofile. These overlapping features underscore the difficulty in conclusively differentiating TA and KHE on biopsy. Correlation with clinical and imaging features (deeper, multiplane involvement is more typical of KHE) is often required for definitive diagnosis between these two entities.


KAPOSIFORM HEMANGIOENDOTHELIOMA


Etiology

KHE is a rare, locally aggressive vascular tumor. In one study, the prevalence of KHE in New England was estimated at 0.91 cases per 100 000 children.39 In the same study, authors estimated that KMP is present in up to 71% of children or infants presenting with KHE.


Clinical Presentation

KHE has a predilection for occurrence on the extremities, but may also occur in the retroperitoneum, head and neck, trunk or groin.40 They present most commonly as a violaceous, indurated plaque or nodule in early infancy. Similar to TA, hypertrichosis or hyperhidrosis may be observed. As discussed earlier, KHE can develop into a KMP more commonly than in tufted hemangiomas. Rapid expansion, bruising, or purpura may be associated with lesions undergoing KMP (Figure 25-13). KHE are often deep and infiltrative; thus, if deep tissues such as muscle or fascia are involved, it may lead to fibrosis and chronic pain later in the course.






FIGURE 25-13. Kaposiform hemangioendothelioma in the inguinal region of an infant. Photo courtesy of Dr. Kristen Hook.


Histologic Findings

KHE demonstrates coalescent lobules of mostly poorly canalized vessels with rounded or spindled endothelial cells (Figure 25-14). Sheets and fascicles of spindled cells which form slit-like vessels resemble those seen in nodular KS. Clusters of cells with a glomeruloid appearance may be seen, similar to those in TA, although these tend to be larger and less circumscribed in KHE. Extension into the subcutis and deeper tissue planes is more common than in TA, and KHE tends to have a more infiltrating architectural pattern. Cytologic atypia is minimal, and mitotic figures are uncommon. Microthrombi are commonly present in capillaries, and hemosiderin may be seen within individual endothelial cells. The interlobular stroma of KHE commonly demonstrates fibrosis, edema, or mucin deposition.41 Lesional cells stain positively for lymphatic markers including D2-40/podoplanin, PROX-1, and other vascular markers such as CD31.41,42 As noted earlier, the differential diagnosis includes nodular KS, although HHV8 staining in KHE is consistently negative.43



PAPILLARY INTRALYMPHATIC ANGIOENDOTHELIOMA (FORMERLY DABSKA TUMOR)


Definition and Epidemiology

Papillary intralymphatic angioendothelioma (PILA or Dabska tumor) was first described in 1969 by Maria Dabska. This borderline malignant vascular tumor occurs almost exclusively in children and young adults.44 PILA tumors are quite rare, and usually involve only the skin and subcutis, although deeper infiltrative PILA tumors have also been described.44 Because of their rarity, their long-term behavior and overall prognoses are not understood. However, it should be noted that in some cases, regional lymph node involvement and at least one case of disseminated metastatic disease resulting in death have been reported.45







FIGURE 25-14. Kaposiform hemangioendothelioma. Tumor with lobulated zones that resemble those of tufted angioma, but also with increased interlobular vessels in a dissecting pattern similar to that of Kaposi’s sarcoma.


Clinical Presentation

Lesions present as ill-defined, erythematous to violaceous vascular plaques or nodules. There are several reports of PILA/Dabska tumors arising in the setting of an underlying lymphatic malformation (LM) or other vascular anomalies.


Histologic Findings

PILA demonstrates both slit-like and widely dilated vascular channels lined by hyperchromatic endothelial cells with prominent hobnailing (Figure 25-15). The characteristic finding is of intravascular papillary clusters (“tufts”) of endothelial cells surrounding a central hyaline core. These tufts may resemble glomeruli and can fill and occlude vascular channels. Dense lymphocytic inflammation may also be present adjacent to vascular structures.22 The differential diagnosis includes papillary endothelial hyperplasia (Masson’s phenomenon), retiform hemangioendothelioma, and the glomeruloid hemangioma associated with POEMS syndrome. The characteristic appearance of tufts in PILA, with eosinophilic cores and surrounding roundish endothelial cells, typically permits distinction.



COMPOSITE HEMANGIOENDOTHELIOMA


Definition and Epidemiology

Composite hemangioendothelioma, so named because it exhibits multiple histologically distinct components (originally described as demonstrating overlapping features of benign, low-grade, and malignant-appearing vascular tumors46), is considered to be a low-grade malignancy with frequent local recurrence and a low risk of lymph node or distant metastasis.47 The majority of cases present in adulthood, although childhood (and rarely congenital48) presentations are described. The overall incidence is unknown, but it is believed to be quite rare; fewer than 40 cases have been reported.49


Etiology

A molecular basis for this rare tumor has not been established. Most are reported to arise sporadically, without underlying comorbidities, although rare associations with vascular malformations, Mafucci syndrome, lymphedema, or prior irradiation have been described. An aggressive variant of composite hemangioendothelioma that expresses neuroendocrine markers has recently been reported.49


Clinical Presentation

Tumors present as slow-growing, nodular masses or zones of ill-defined soft tissue swelling, most commonly on the lower extremities, up to 6 cm in diameter.46 Patients may report pain. Surface skin changes may include purpura, a violaceous hue, or alopecia.50

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May 8, 2019 | Posted by in Dermatology | Comments Off on Vascular Lesions
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