Generally, endovascular papillary angioendothelioma presents as a slow-growing, painless nodule that is typically localized to the subcutaneous tissue of the extremities, dermis, and less commonly on the trunk, head, and neck.[11] Some cases have been reported in deeper locations such as the bone, brain, spleen, tongue, and testis.[8] Notably, no other primary sources were discovered in these instances, nor was lymph node involvement identified.[6]

Most cutaneous tumors come to medical attention when they are two to three centimeters in size.[15] However, much larger lesions have been reported, and have been seen up to 40 centimeters in diameter. The tumors may vary in appearance. Some are described as an ill-defined mass, a plaque, or a nodule with projections into the surrounding tissue. The overlying skin may be pink, blue, or violaceous in color with an atrophic dermis.

Symptomatology is also variable. Patients may complain of pain, ulceration, or bleeding from the affected site.[6] Though these lesions tend to be low grade, cases of regional nodal involvement and pulmonary metastasis have been reported in the literature.[16] Hence, it is essential for complete physical evaluation, including a metastatic workup.

The definitive diagnosis of EPA is made with a biopsy. As this is such a rare entity, protocols for disease involvement, surveillance, and follow-up have yet to be established. It is reasonable to consider obtaining a chest radiograph for any patient with pulmonary symptoms due to a reported case of a patient dying of pulmonary metastases. Lymph node examination may be performed if there is suspicion for involvement.[15]

Surgical excision is recommended. In general, the prognosis is favorable for Dabska tumors even with invasion into deeper structures. However, the malignant potential of this tumor should not be ignored, and close follow-up should be maintained.[6] Regional lymphadenectomy should be performed when those structures appear involved.[15]

In one case report, the authors chose to follow National Comprehensive Cancer Network (NCCN) practice guidelines in oncology for soft tissue sarcoma of extremity/trunk stage IIA (T1bN0M0G2), which recommends chest imaging (plain radiograph or chest computed tomography) every 3 to 6 months for 2 to 3 years, then every six months for two years, and then annually for ongoing monitoring.[6]

The differential diagnosis of this tumor is histologic, as many neoplasms display intravascular proliferation. The differential should include intravascular papillary endothelial hyperplasia (Masson tumor), epithelioid hemangioendothelioma, angiosarcoma, lymphangioma-like Kaposi sarcoma, and retiform hemangioendothelioma.[7]

The unique feature of EPA is the papillary structure lined by atypical columnar endothelial cells. A similar formation has been described extravascularly in the patch stage Kaposi sarcoma. Ordinary angiosarcomas may also show focal morphologic patterns of EPA, and in a study of 80 cases of angiosarcoma of soft tissue, 14% showed evidence papillary fronds.[16] Angiosarcoma, however, shows more significant endothelial atypia and diffuse growth outside of blood vessels.[7]

Organized thrombi cause the Masson phenomenon, showing papillary processes of the fibrous cores covered with a layer of endothelial cells. Unlike EPA, the Masson phenomenon is contained within blood vessels, and there are often visible intravascular thrombi. It lacks the presence of columnar endothelial cells and has a single endothelial cell layer surrounding hyalinized stromal cores.[7]

Epithelioid hemangioendothelioma display endothelial cells with eosinophilic vacuolated cytoplasm. The tumor cells arrange as cords, trabeculae, or sheets with myxoid or hyalinized stroma, and often spread outside of the blood vessel.[7]

Of note, there have been reports in the literature of benign acquired vascular proliferations displaying areas with Dabska features simulating malignancy. Therefore, the presence of atypical architectural features in an otherwise benign-looking acquired vascular proliferation should not lead to unnecessarily aggressive treatment.[17]

Currently, wide local excision remains the treatment of choice for these tumors.[16] In most of the patients, this treatment is sufficient without any recurrence. However, a few cases of lymph nodal involvement and pulmonary metastasis have been reported, thus advocating the need for close follow up and long term evaluation.[16]

Evidence for radiation therapy in these tumors is limited. Of the six patients reported by the Dabska et al. group, three received radiation therapy; of these, two received preoperative radiation while one received it after surgery.[14] Those who received preoperative radiation did not report any response; however, this could be due to the suboptimal dose delivered to these patients. The recommended radiation dose in the preoperative setting for sarcomas is around 50Gy, and the dose they received was around 30Gy. Currently, there are no recommendations for radiation therapy; however, due to deep invasion features observed, it may play a role in the recurrent setting.

Due to the rarity of these tumors, the benefit of radiation therapy in a randomized trial would be difficult to obtain. Hence it would be prudent to consider radiation in tumors showing features of a high risk of recurrences such as size > 5 cm, deep invasion, and positive margins based upon their behavior pattern similar to low-grade sarcomas.

Due to the rarity of these tumors, it is challenging to obtain level I evidence for treatment recommendations. Currently, the practice guidelines are obtained from published case series and reports.

Patterns of failure are yet to be determined for this rare tumor; meanwhile, it would be prudent to consider radiation in a post-operative setting for tumors exhibiting high-risk features for recurrence. Dose, technique, and volume delineation should be based on the principles of radiation therapy in sarcoma.

Based on the literature review, the role of systemic therapy remains yet to be established. Chemotherapy has shown response in angiosarcomas; there may be a role for chemotherapy in the metastatic setting.[18] It is highly recommended for institutions to report their experience with radiation therapy and systemic therapy, which will further add to the literature and guide others in treating these rare tumors with the best possible approach.

In general, endovascular papillary angioendothelioma are low-grade tumors with favorable outcomes managed with surgery alone. Long term review of originally described patients with Dabska tumors has reported excellent outcomes.[14] However, lymph node metastasis and pulmonary metastasis have been documented, so close follow up and evaluation is warranted.[16]

Endovascular papillary angioendothelioma are slow-growing tumors with favorable prognosis. However, there have been reports of pulmonary metastasis; hence these tumors are not to be underestimated and should be evaluated and treated in time.

Endovascular papillary angioendothelioma must be kept in the differential, especially for children presenting with slow-growing intradermal nodules and evaluated accordingly. Awareness among dermatologists is crucial, as most likely, they will be the primary providers to whom the children will present.

Endovascular papillary angioendothelioma, also known as Dabska tumor and papillary intralymphatic angioendothelioma, is a rare tumor of deeper skin. The diagnosis is made with a biopsy. Because of the vast differential for a painless skin lesion, the management should be by an interprofessional team that consists of a dermatologist, plastic surgeon, oncologist, and general surgeon.

Primary clinicians who are not familiar with the management of such lesions should refer the patient to an oncologist. EPA has an overall favorable prognosis, but it does have the potential for local recurrence and low-grade metastasis. Thus, long term follows up is required.