Benign Florid Vascular Proliferation Mimicking Vascular Neoplasm

Etiology

Colonic florid vascular proliferation is most commonly associated with intussusception and colonic obstruction. The literature review has also demonstrated the association of florid vascular proliferation with mucosal prolapse, lipomas, human immunodeficiency virus, cytomegalovirus, and Meckel diverticulum.[6][7]

Epidemiology

Florid vascular proliferation usually involves middle-aged and older adults, but there have been some cases in infants with cytomegalovirus infection.[5][3] The most common site for occurrence is the colon, followed by the small intestine, appendix, and Meckel diverticulum.[8][9][3]

Pathophysiology

The possible mechanisms for florid vascular proliferation include, continued mechanical forces on the bowel wall as encountered in intussusception; or maintained stresses on a chronic ulcer, which in turn leads to bowel hypoperfusion and/or ischemia and ultimately reactive vascular proliferation.[5]

Histopathology

Histologically, florid vascular proliferation demonstrates granulation tissue-type florid proliferation of small vascular channels in a lobular arrangement. The vascular channels' lining is plump endothelial cells involving the entire thickness of the bowel wall, expanding from the submucosa to subserosal connective tissue. The endothelial cells have mild nuclear atypia with few to no mitosis. The overlying mucosa of the lesion demonstrates ulceration with ischemic-type changes and some features of mucosal prolapse with underlying fibrosis.[3][5] Focal areas of organizing thrombus-like changes may present. With immunohistochemical stains, the vasculature endothelial cells are positive for CD31 and CD34 and negative for HHV-8.[9]

History and Physical

The most common site of florid vascular proliferation is a colon, which explains most of the symptoms associated with this lesion. Patients usually present with abdominal pain, melena, diarrhea, and sometimes bleeding. In some cases, when the size of the lesion is large, patients may also present with a "mass" effect, demonstrating signs and symptoms of bowel obstruction or intussusception.[5]

Evaluation

Although different radiology diagnostic modalities such as barium enema, CT scan, magnetic resonance imaging (MRI) and colonoscopy, can be used to demonstrate a possible "mass" in the gastrointestinal tract, none of these techniques are specific.[5][[7] A definitive diagnosis of FVP can only be achieved by tissue biopsy with microscopic examination. And in most cases, complete resection of the lesion is needed for a correct diagnosis.

Treatment / Management

In symptomatic cases, complete surgical excision is the treatment of choice. Since florid vascular proliferation is a benign reactive lesion, there are no reports of reoccurrence reported in published English literature, and no additional treatment is required postoperatively.

Differential Diagnosis

The most crucial entity in the differential diagnosis is angiosarcoma. The gastrointestinal angiosarcoma is rare, and it usually involves the small intestine. Angiosarcoma is composed of atypical epithelioid tumor cells arranged in solid sheets with only subtle vasoformation. Brisk mitosis and necrosis are common presentations in angiosarcoma.  However, florid vascular proliferation usually demonstrates a more obvious capillary architecture in a lobular growth pattern. Mitosis is none or infrequent. The endothelial cells in FVP do not have significant cytologic atypia. Furthermore, the finding of mucosal prolapse-type changes, such as muscular fibroplasia, is very helpful for a diagnosis of FVP. The diagnosis of angiosarcoma of the GI tract is only possible after the exclusion of florid vascular proliferation and other benign vascular lesions.[3]

The second entity in the differential diagnosis is Kaposi sarcoma (KS). Kaposi sarcoma is a malignant neoplasm associated with human herpesvirus-8 (HHV-8), usually involving patients with immune deficiency.[1] Microscopically, the morphologic features that differentiate Kaposi sarcoma from florid vascular proliferation are compressed, slit-like vascular channels with extravasated erythrocytes, hemosiderin, and plasma cells. Mitoses are common, but nuclear pleomorphism is usually minimal in Kaposi sarcoma.  Positive HHV-8 immunostain can also help to differentiate Kaposi sarcoma from florid vascular proliferation. 

Other benign vascular lesions, such as hemangiolymphangiomas (HLAs), vascular malformations, or angiogenic polypoid proliferation, should also be considered in the differential diagnosis. HLAs are commonly polypoid lesions, ranging from 0.5 cm to 3.5 cm. Microscopically, HLAs show proliferation of capillaries, veins, or lymphatics, involving the mucosa or submucosa only, and is not transmural. Vascular malformations are more common in women and grossly appear as “congestive streaks” that may range in size from 0.6 cm to 3 cm. Microscopically, they are composed of submucosal clusters of abnormal, variably sized vessels of different types, including arteries/arterioles, capillaries, veins/venules, and lymphatics. Mucosal ulceration or erosion is common in vascular malformation. Angiogenic polypoid proliferation of the small bowel typically occurs in the lamina propria and is not transmural; this was initially thought to be a paraneoplastic process of the mucosa surrounding small intestinal well-differentiated neuroendocrine tumors. However, Abraham et al. noted in a comparison cohort study that the researchers identified angiogenic polypoid proliferation in a majority of non-carcinoid neoplasms.[10] Thus, angiogenic polypoid proliferation is not specific to carcinoids. It can also occur in a variety of tumor types and seem to be rather an exaggerated form of mucosal prolapse.[10]

In summary, florid vascular proliferation is a benign pseudo-neoplastic vascular proliferation that may mimic other benign or malignant vascular lesions or neoplasms. Correct diagnosis of this entity is essential since this lesion is benign and does not appear to recur after complete surgical excision.[8]

Prognosis

Florid vascular proliferation usually is remarkable for an excellent prognosis after local surgical excision. In the most extensive series of five patients, no recurrences were seen with up to five-year follow-up postoperatively.[7][3]

Complications

Complete surgical excision is the treatment of choice. There are no reported complications in published English literature.[3]