(1)
Department of Pathology, University of Manitoba Max Rady College of Medicine, Winnipeg, MB, Canada
Keywords
AngiosarcomaEpithelioid hemangioendotheliomaKaposiform hemangioendotheliomaKaposi sarcomaVascular lesion s are primarily composed of the endothelial cells that line the arteries , veins , or lymphatics (Fig. 10.1a–c). Given the ubiquitous nature of these circulatory elements within the human body, it should come as no surprise that vascular neoplasms can arise in numerous anatomic locations.
Fig. 10.1
(a) Flat endothelial cells lining an arteriole (arrow). (b) Endothelial cells lining a vein (arrow). (c) Endothelial cells lining a lymphatic space (arrow)
Benign vascular lesions include numerous entities such as vascular malformations, reactive vascular proliferations, and hemangiomas. As multidisciplinary musculoskeletal groups tend to focus on the more aggressive vascular tumors in daily practice, this chapter will primarily discuss vascular tumors that are intermediate or malignant in behavior.
10.1 Kaposi Sarcoma
Kaposi sarcoma is a malignant vascular tumor that was frequently encountered in North America during the HIV epidemic . It can arise in multiple locations, such as the skin, lymph nodes, or gastrointestinal tract. This tumor is associated with the human herpes virus 8 (HHV-8 ) infection and is subcategorized based on clinical presentation.
In AIDS-related Kaposi sarcoma , the lesions occur in the skin, mucosal surfaces, andinternal organs in patients with advanced HIV. In endemic (African) Kaposi sarcoma , the tumor presents in young African males as multiple enlarged lymph nodes. In classic Kaposi sarcoma, patients are typically men of African, Eastern, or Middle European descent that present with multiple blue cutaneous lesions. Iatrogenic (transplantation-related) Kaposi sarcoma can be seen in renal transplant patients [1].
Pathology
The microscopic appearance of Kaposi sarcoma depends on the stage of clinical progression. In the earliest (patch) stage of Kaposi sarcoma, the features are extremely subtle, with the skin showing a vague increase in dermal vascular spaces lined by bland endothelial cells and mild associated chronic inflammation. As this lesion progresses to the plaque stage, this neoplasm encompasses most of the dermis with the endothelial cells displaying a spindled appearance and a vaguely fascicular architecture (Figs. 10.2 and 10.3). Associated scattered round eosinophilic globules and chronic inflammatory cells can be seen (Fig. 10.4) [2].
Fig. 10.2
Spindle cells of a Kaposi sarcoma arranged in a fascicular architecture
Fig. 10.3
The spindle cells of this Kaposi sarcoma do not show extensive atypia
Fig. 10.4
Kaposi sarcoma has prominent chronic inflammation. Rare eosinophilic globules can also be identified (arrow)
Ancillary Studies
Kaposi sarcomas are positive for endothelial cell markers such as CD31, CD34, and ERG.
Latency-associated nuclear antigen (LANA-1 ) is associated with HHV-8 infection. Positive immunohistochemical staining for this protein in an endothelial lesion is both sensitive and specific for Kaposi sarcoma (Fig. 10.5) [3].
Fig. 10.5
Endothelial cells of Kaposi sarcoma are positive for LANA-1, consistent with HHV-8 infection
Differential Diagnosis
Angiosarcoma
Spindle cell hemangioma
Comment
- 1.
The spindling nature of Kaposi sarcoma can be confused for angiosarcoma or spindle cell hemangioma. HHV-8 staining distinguishes Kaposi sarcoma from these other vascular tumors.
- 2.
Appropriate suspicion based on the patient’s clinical presentation (e.g. organ transplant, HIV) is helpful in assuring appropriate morphologic assessment and use of the HHV-8 stain.
- 3.
If left untreated, AIDS-associated Kaposi sarcoma has a mortality rate of 90% [4].
- 4.
In patients who have an intact immune system, Kaposi sarcoma has a mortality rate of approximately 10–20%.
- 5.
Systemic therapy is used for persistent, metastatic, or systemic disease [4].
- 6.
Kaposi sarcoma arising in HIV can be appropriately treated with HAART therapy. After the introduction of this treatment regimen, the incidence of AIDS and Kaposi sarcoma in North America has dramatically decreased [5].
10.2 Epithelioid Hemangioendothelioma
Epithelioid hemangioendothelioma is a malignant vascular tumor that often presents as a painful mass associated with a vessel. These occur in adults (median age of 50 years) and frequently arise in the extremities, head and neck, trunk, and mediastinum. Other sites of occurrence include the lung, bone, and liver [2, 6].
Pathology
Microscopically, these tumors are composed of round to ovoid cells arranged in strands and sheets in the background of myxoid or hyalinized stroma (Fig. 10.6). These cells can obstruct and circumscribe a vascular space (Fig. 10.7). Intracellular lumens containing erythrocytes are often seen (Fig. 10.8) [7].
Fig. 10.6
Neoplastic endothelial cells of epithelioid hemangioendothelioma in a myxoid and hyalinized background
Fig. 10.7
Vein obstructed by tumor cells (arrow) of an epithelioid hemangioendothelioma
Fig. 10.8
Occasional erythrocytes are present in the intracellular lumens of this epithelioid hemangioendothelioma (arrow)
Ancillary Studies
Immunohistochemically, the tumor cells are positive for endothelial markers such as CD31, ERG, and CD34.
Epithelioid hemangioendotheliomas show characteristic WWTR1-CAMTA1 or YAP1-TFE3 fusion transcripts.
Epithelioid hemangioendotheliomas are often positive for an anti-CAMTA1 antibody [8].
Differential Diagnosis
Epithelioid angiosarcoma
Carcinoma
Epithelioid hemangioma
Comment
- 1.
Epithelioid hemangioendothelioma can be mistaken for other epithelioid neoplasms such as epithelioid angiosarcoma, carcinoma, or epithelioid hemangioma.
- 2.
Epithelioid angiosarcoma shows greater nuclear atypia and mitosis than epithelioid hemangioendothelioma. A positive anti-CAMTA1 antibody can be helpful in distinguishing the two lesions.
- 3.
Epithelioid hemangioendotheliomas can focally stain for keratin stains such as AE1/AE3. However, carcinomas are virtually never positive for CD34 or other vascular markers.
- 4.
Epithelioid hemangiomas typically have associated inflammation and lack the hyalinized or myxoid background seen in epithelioid hemangioendothelioma.
- 5.
Overall, 20–30% of epithelioid hemangioendotheliomas metastasize, usually either to the lung or lymph node.
- 6.
Consequently, these tumors are now considered malignant and have an overall 5-year survival rate of 80%.
- 7.
However, tumors with less than three mitoses per 50 high power fields (hpf) and less than 3 cm in size demonstrate a 5-year disease-specific survival rate of 100% [9].
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