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Case Report |
1
Department of Radiology, Box 0628, University of California School of
Medicine, San Francisco, CA 94143.
2
Department of Radiology (114), Veterans Affairs Medical Center, UCSF, 4150
Clement St., San Francisco, CA 94121.
3
Department of Anatomic Pathology, Box 102, University of California School of
Medicine, San Francisco, CA 94143.
Received April 30, 1999;
accepted after revision July 9, 1999.
Address correspondence to J. Yee.
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Transabdominal sonography (Sonoline Elegra; Siemens, Erlangen, Germany) was performed using a 3.5-MHz transducer and revealed splenomegaly with a mottled echo texture of the spleen but no discrete focal masses (Fig. 1A). Doppler sonography did not reveal any areas of abnormal vascularity. Helicat CT (CT/i; General Electric Medical Systems, Milwaukee, WI) of the abdomen, after injection of 150 ml of contrast material at 2 ml/sec, was performed using a collimation of 7 mm and a pitch of 1. Contrast-enhanced images showed an enlarged spleen measuring 16.5 cm in length, containing multiple small hypodense lesions on portal venous phase images obtained 80 sec after the start of the contrast material injection. The splenic parenchyma appeared diffusely heterogeneous and contained multiple ovoid hypodense foci measuring 5-10 mm in diameter (Fig. 1B). No dominant splenic masses, cystic areas, or calcifications were present. No associated abdominopelvic lymphadenopathy was detected. Delayed images were obtained approximately 15 min after the start of the contrast material injection; previously seen lesions had become isodense with the remaining splenic parenchyma and were difficult to visualize (Fig. 1C).
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The spleen was surgically removed, and subsequent histologic examination revealed multiple nodules consisting of large vascular spaces with small anastomotic vascular channels, some of which joined to normal peripheral splenic sinuses. Lining cells were flat with grooved nuclei. Mild nuclear pleomorphism was present, but mitotic figures were rare (Figs. 1D, 1E, 1F, 1G). These findings were considered diagnostic of benign splenic littoral cell angioma.
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Patients with littoral cell angioma of the spleen clinically present with relatively benign findings of hypersplenism such as splenomegaly, thrombocytopenia, or anemia. In many cases, this splenic tumor is discovered incidentally during abdominal surgery performed for another reason. The distribution between men and women is nearly equal.
In this report, we present the CT and sonographic characteristics of a pathologically proven case of diffuse littoral cell angioma of the spleen. On contrast-enhanced CT performed during the portal venous phase, the spleen has multiple small ovoid areas of low attenuation, ranging in size from 5 to 10 mm. These CT findings correlate well with the gross and histologic findings of the spleen with littoral cell angioma. Delayed filling of the nodules eventually makes the nodules isodense with the surrounding enhancing splenic tissue. Sonographic characteristics are less defined and include a diffuse, coarse, heterogeneous echo texture of the spleen.
The radiologic differential diagnosis for littoral cell angioma of the spleen includes primary splenic neoplasms that lead to diffuse involvement: hemangiomatosis, lymphangiomatosis, hamartoma, hemangiopericytoma, hemangioendothelioma, and angiosarcoma. The least common form of splenic hemangioma that involves the spleen in a diffuse manner, hemangiomatosis, may exhibit an enhancement pattern similar to that of hemangiomas of the liver, with peripheral nodular enhancement that fills in centripetally and becomes hyperdense to surrounding normal splenic parenchyma; however, the cavernous form of splenic hemangiomas may remain avascular and hypodense [4]. Lymphangiomatosis is a benign neoplasm of the spleen composed of endothelium-lined cystic spaces containing proteinaceous fluid. These cystic spaces appear hypodense on unenhanced and contrast-enhanced CT. On sonography, the cystic nature of this neoplasm is confirmed by the presence of multiple anechoic nodules of various sizes with posterior acoustic enhancement. Hamartomas are composed of an anomalous mixture of disorganized proliferation of vascular channels that are hypodense on unenhanced CT and show moderate and heterogeneous contrast enhancement. Sonography shows an echogenic mass that may contain cystic areas.
Both benign and malignant forms of hemangiopericytomas occur and manifest as numerous small confluent nodules distributed throughout the spleen. The solid portions of hemangiopericytoma are hypervascular and enhance intensely with contrast material; however, the tumor also has a cystic portion that remains hypodense after administration of contrast material. Hemangioendotheliomas typically occur as multiple nodules in the liver of infants and are composed of a proliferation of small vascular channels lined by endothelial cells. Rarely, the spleen may also be involved. These lesions appear as well-defined hypodense lesions on unenhanced CT. After contrast material administration, peripheral enhancement is seen, similar to that seen with hemangiomas. Variable centripetal enhancement occurs. Cavernous areas and regions of hemorrhage and calcification may be present. The appearance on sonography is variable, and hypoechoic or hyperechoic nodules may be seen. Splenic angiosarcomas may present in a diffuse infiltrating form that is seen as a diffuse nodular process on cross-sectional imaging [5]; however, splenic angiosarcomas also typically possess imaging characteristics suggestive of a malignant process such as ill-defined borders, necrosis, hemorrhage, and extrasplenic tumor extension. Other associated findings of angiosarcoma include splenomegaly and hemorrhagic rupture.
Metastatic disease and lymphoma may also affect the spleen in a diffuse manner, leading to a nodular appearance. Hypoechoic nodules are the characteristic sonographic findings of both metastases and lymphoma. Additionally, a bull's eye appearance on sonography can occur with both neoplasms but is more common with metastases. After IV contrast material administration, splenic metastases and lymphoma typically appear as hypodense lesions with variable enhancement. The primary sites of tumor that produce cystic splenic metastases are ovary, breast, endometrium, and melanoma. Patients with splenic metastases and lymphoma will also typically have evidence of nodal disease, which is not present in patients with littoral cell angioma.
Sarcoidosis may involve the spleen in a diffuse manner. Histologically, this disease is characterized by noncaseating granulomas. On CT, irregularly distributed low-density lesions are seen in an enlarged spleen. Associated abdominal adenopathy is also present in most patients. The sonographic features of splenic sarcoidosis include, in a diffuse manner, increased echogenicity of the splenic parenchyma with focal hypoechoic or mixed echogenic lesions.
Kaposi's sarcoma may also affect the spleen and mimic a primary vascular tumor, typically in immunocompromised patients. Splenic peliosis is a rare entity that also occurs in patients with AIDS. Peliotic lesions may have a variable enhancement pattern and do not tend to involve the spleen in a diffuse manner.
Lastly, infectious processes that lead to microabscess formation may mimic splenic littoral cell angioma. Fungus, Pneumocystis carinii, and infections from Mycobacterium species may cause multiple microabscesses of the spleen that are hypodense on contrast-enhanced CT. On sonography, the microabscesses may appear homogeneously hypoechoic or may exhibit a bull's eye appearance with an echogenic center and a hypoechoic rim. Calcification is commonly seen with particular infections such as tuberculosis, histoplasmosis, and pneumocystis pneumonia.
Littoral cell angioma is a benign neoplasm of the spleen that must be considered in the differential diagnosis of multiple small hypodense nodules seen on the portal venous phase on contrast-enhanced CT. This appearance can mimic malignant processes, such as metastatic disease, lymphoma, and Kaposi's sarcoma, as well as infections that cause microabscesses. Sonographic findings were less helpful in our patient because the splenic nodules of littoral cell angioma were not apparent.
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  S. Bhatt, J. Huang, and V. Dogra Littoral Cell Angioma of the Spleen Am. J. Roentgenol., May 1, 2007; 188(5): 1365 - 1366. [Full Text] [PDF]
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 S. Bhatt, R. Simon, and V. S. Dogra Littoral Cell Angioma: Sonographic and Color Doppler Features J. Ultrasound Med., April 1, 2007; 26(4): 539 - 542. [Full Text] [PDF]
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 R. M. Abbott, A. D. Levy, N. S. Aguilera, L. Gorospe, and W. M. Thompson From the Archives of the AFIP: Primary Vascular Neoplasms of the Spleen: Radiologic-Pathologic Correlation RadioGraphics, July 1, 2004; 24(4): 1137 - 1163. [Abstract] [Full Text] [PDF]
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 A. D. Levy, R. M. Abbott, and S. L. Abbondanzo Littoral Cell Angioma of the Spleen: CT Features with Clinicopathologic Comparison Radiology, February 1, 2004; 230(2): 485 - 490. [Abstract] [Full Text] [PDF]
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