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Radiologic-Pathologic Conference of the University of Rochester School of Medicine and Dentistry |
1 Department of Radiology, University of Rochester School of Medicine and
Dentistry, 601 Elmwood Ave., Box 648, Rochester, NY 14642.
2 Department of Pathology, University of Rochester School of Medicine and
Dentistry, Rochester, NY.
Received August 29, 2006; accepted after revision October 31, 2006.
Address correspondence to V. Dogra.
Keywords: littoral cell angioma • radiologic-pathologic • spleen
Littoral cell angioma of the spleen is a rare vascular tumor that was first described by Falk et al. [1] in 1991. The tumor arises from the littoral cells in the splenic red pulp sinuses. Littoral cell angioma affects both men and women equally with no specific age predilection. It is usually asymptomatic and is discovered incidentally. Some of the patients with this entity may present with symptoms of hypersplenism such as anemia, thrombocytopenia, and splenomegaly, the latter seen in almost all patients with littoral cell angioma.
Clinically, a majority of the littoral cell angiomas described in the literature have been found to be benign in nature, but several reports have described malignancy in the littoral cell angioma [2]. Definite evaluation can only be done at pathology.
Most of the cases of littoral cell angioma described in the literature have been composed of multiple nodules of varying sizes in the spleen [2, 3]; only one case of focal angioma has been described [4].
Our patient was a 56-year-old man who, while being evaluated for thigh leiomyosarcoma, was found to have splenomegaly with hypodense splenic lesions. The patient did not show any signs or symptoms of hypersplenism. Unenhanced and contrast-enhanced portal venous phase CT was performed, which revealed multiple splenic lesions with enhancement (20 H). Because the patient had a history of malignant melanoma and existing thigh leiomyosarcoma, the splenic lesions were suspected to be metastatic in origin. Because of the concern for malignancy, a splenectomy was performed. Pathology revealed the presence of multiple foci of brown-black friable areas, the largest being 4.5 cm. This lesion extended up to the capsule but did not penetrate it. An immunohistochemical study confirmed the histologic diagnosis of littoral cell angioma by showing the cells positive for CD31, CD68, and factor VIII.
Radiologic Features
On CT imaging, littoral cell angioma appears as a hypoattenuating nodule or nodules ranging in size from 5 to 6 cm and demonstrating contrast enhancement on the portal venous phase (Fig. 1A). Delayed phase imaging shows the nodules to become isodense to the surrounding splenic parenchyma because of delayed filling of the nodules [5]. Radiologic findings can rarely lead to a definitive diagnosis because many other splenic neoplasms have a similar appearance. Other splenic neoplasms that mimic littoral cell angioma include hemangiomatosis, lymphangiomatosis, hamartoma, hemangiopericytoma, hemangioendothelioma, and angiosarcoma; malignant processes such as metastases, lymphoma, and Kaposi sarcoma; and infectious processes such as Pneumocystis and Mycobacterium [5].
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Pathologic Features
Definite diagnosis of littoral cell angioma can only be made at pathology after splenectomy, which is usually performed because of the concern for malignancy.
The gross cut surface of the spleen shows nodules with blood or blood products with a variable color from dark red or brown to black, depending on the chronicity of the blood in the lesion. Histopathologically, littoral cell angioma is characterized by the presence of anastomosing vascular channels, which are lined by tall endothelial cells and papillary fronds extending into the vascular channels [1-3] (Fig. 1B). Some exfoliated cells may also be found within the vascular spaces. The lesions do not have a capsule but are well delineated from the surrounding splenic parenchyma.
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Littoral cell angioma is a benign vascular tumor of the spleen. It shares some morphologic and immunohistochemical features with hemangiomas of other sites such as immunoreactivity for vascular endothelial markers CD31 and factor VIII. However, it is unique in that almost all cases also express histiocytic marker CD68. It has been proposed, based on the expression of CD68 by the tumor cells, that this tumor may have its origin in the splenic sinus lining cells or littoral cells [1].
In conclusion, littoral cell angioma, although a pathologic diagnosis, should be considered in the differential diagnosis in the presence of multiple hypoattenuating nodules in the spleen, particularly in the presence of symptoms of hypersplenism.
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