Provisionally unclassified vascular anomalies
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# Overview
International Society for the Study of Vascular Anomalies (ISSVA) has now classified vascular anomalies into vascular tumors and vascular malformations with an unclassified category for lesions that show clinical and histological characteristics unique from disorders classified in vascular tumors and vascular malformations.

# Provisionally unclassified vascular anomalies

## Intramuscular hemangioma
- Intramuscular heamangioma is characterized by benign proliferation of vascular channels. Majority of lesions occur in subcutaneous adipose tissues, followed by muscles. Thigh and calf are most common sites of occurrence. Majority of the lesions are asymptomatic. Typical clinical presentation includes chronic pain and swelling, both may increase with exercise of affected muscle due to increased blood flow. Other clinical manifestations may include pulsations, discoloration over the lesion, lesion enlargement when in dependent position, increased temperature, muscle contracture, tenderness, and muscle weakness and fatigue.
- Intramuscular hemangiomas may be associated with Kasabach-Merritt syndrome characterized by thrombocytopenia and/or consumptive coagulopathy. This lesion may also lead to functional impairment, congestive cardiac failure due to arteriovenous shunting, pressure symptoms, skin necrosis and may also erode bone.
- Etiology and pathophysiology are not clearly defined but majority of the lesions are congenital while a one-fifth may be associated with trauma.
- MRI is the diagnostic study of choice although X-ray and ultrasound may be used as initial studies. Treatment is generally not indicated for asymptomatic lesions. Management options for symptomatic, complicated lesions and for cosmetic reasons may include laser ablation, systemic corticosteroids, cryotherapy, embolization, radiation, compression sclerotherapy, and surgical excision although surgical excision is usually treatment of choice in majority of the cases.

## Angiokeratoma
- Angiokeratoma is a  mucocutaneous vascular lesion with wart-like papular appearance characterized by dilated capillaries in the dermis and hyperkeratotis of the overlying epidermis. Clinically, it may manifest as solitary or multiple hyperkeratotic papules that may be localized or generalized, most typically on scrotum, thighs, lower extremity, abdomen, trunk, tongue, penis and labia majora. Majority of the lesions are asymptomatic but some may ulcerate and/or bleed.
- It may be classified into following entities:
Fordyces angiokeratoma (arising on the genitals)
Mibellis angiokeratoma (dorsum of toes and fingers)
Angiokeratoma circumscriptum naeviforme (unilateral large keratotic plaques)
Angiokeratoma corporis diffusum (ACD) (generalized lesions between umbilicus and the knee)
- Fordyces angiokeratoma (arising on the genitals)
- Mibellis angiokeratoma (dorsum of toes and fingers)
- Angiokeratoma circumscriptum naeviforme (unilateral large keratotic plaques)
- Angiokeratoma corporis diffusum (ACD) (generalized lesions between umbilicus and the knee)
- Angiokeratomas are more prevalent among males as compared to females. Increased venous pressure and radiation therapy have been cited as possible causes. Angiokeratomas have been associated with enzyme deficiencies such as  alpha-galactosidase A (Fabry disease), -fucosidase (fucosidosis), neuraminidase (sialodosis), aspartyl glycosaminase (aspartyl glucosaminuria), -mannosidase (- mannosidosis), -N-acetyl galactosaminidase (Kansaki disease), and -galactosidase (adult onset GM1 gangliosidosis).
- The diagnosis is mainly clinical but biopsy may be required. Associated enzyme deficiencies and systemic disorders must be ruled out. Treatment is generally not indicated but if so required then excision, electrocautery, cryotherapy, or laser ablations are the options.
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## Sinusoidal hemangioma
- Sinusoidal hemangioma is a variant of cavernous hemangioma characterized histopathologically by presence of dilated thin-walled vascular channels, that vary in size, exhibiting nodular proliferation with sinusoidal arrangement.  Pseudopapillary structures may also be present. Clinically majority of the lesions manifest in female adults as single, well-defined, painless, subcutaneous nodule with bluish color. Most frequent locations are trunk, extremities, and breasts. Painless swelling is the most common patient complaint.
- Abnormalities of vasculogenesis and angiogenesis have been proposed as possible pathogenesis but it is not well-established.
- Combination of clinical manifestations and histopathological features is used for diagnosis. Surgery (wide excision of tumor) is the treatment of choice if treatment is required.
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## Acral arteriovenous "tumour"
- Congenital or acquired lesion manifesting clinically as asymptomatic mass or may present with pulsatile swelling, headache, localized throbbing pain, tinnitus and bleeding. Histopathologically, they are characterized by arterio-venous connection without connecting capillary with or without intracranial component. The lesion derived its name from its acral distribution.
- Etiology can be classified as following: Congenital, traumatic, infectious and inflammatory and familial.
- Although diagnosis can be made clinically, angiography is the gold standard diagnostic modality to diagnose and define the extent of the lesion. Management regimen may include surgical excision, ligation of the supplying arteries, embolization, and intralesional sclerosing injection.

## Multifocal lymphangioendotheliomatosis with thrombocytopenia / cutaneovisceral angiomatosis with thrombocytopenia (MLT/CAT)
- Rare congenital disorder characterized by proliferation of vascular channels in multiple organs associated with thrombocytopenia of variable degree. Lesions may manifest themselves on skin, gastrointestinal tract, lungs, brain, bone, liver, spleen and muscles. Majority of cutaneous lesions present as multiple red to blue papules, plaques, nodules on trunk and extremities. Gastrointestinal bleeding due to multiple hemorrhagic lesions is the cause of mortality in majority of the patients. Similar lesions in brain and lungs may cause severe cerebral edema and pulmonary hemorrhage.
- Disease may manifest without cutaneous involvement or thrombocytopenia. Biopsy typically reveals proliferation of well differentiated vascular channels with intravascular papillary structure and thrombi, sometimes with hobnail appearance of lining endothelial cells.
- Biopsy followed by histopathological and immunohistochemical are required for diagnosis. Management is not well-established and disorder has a poor prognosis with high mortality. Recently sirolimus and bevacizumab have been used to treat this disorder with some success.

## Fibro adipose vascular anomaly (FAVA)
- Vascular disorder typically manifesting as infiltration of muscles by fibrofatty tissues, atypical venodilation associated with localized pain, and contracture of the affected muscles. Majority of the lesions involve calf muscles and may present as painful mass, contracture of the extremity, and decreased dorsiflexion at ankle joint. Skin is not typically involved. Histological studies demonstrates fibrous and adipose tissue and congregations of venous channels with abnormal lymphatic component.
- Somatic activating mutations in PIK3CA that encodes phosphatidylinositol 3-kinase (PI3K), an enzyme functioning in cell growth, proliferation, differentiation, and survival.
- Clinical and radiological findings are often sufficient to form the diagnosis. Inconclusive cases my require biopsy. Surgical resection is the often the preferred treatment and is more effective than sclerotherapy, the alternative therapy.