Stuart Bentley-Hibbert, Ahmed Abdelbaki, Khaled M. Elsayes
The Main Differential Diagnoses of Peripherally enhancing small lesion (single or multiple) include:
Hemangioma: More likely single than multiple, can be atypical (mildly hyperintense, could be homogeneously enhancing, may not fill on delayed phase).
Metastases: Rare, peripheral or homogeneous enhancement (in hypervascular malignancies such as neuroendocrine and RCC), multiple more than single.
Littoral cell angioma: Very rare, can demonstrate homogeneous delayed enhancement, more multifocal than solitary, low signal on TI and T2.
Hemangioma
Usually measuring <2 cm,="" hemangioma="" is="" the="" most="" common="" primary="" neoplasm="" of="" the="" spleen="">45]. The tumor is more likely to appear as a solitary lesion rather than as multiple lesions. Hemangiomas usually exhibit low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. Small hemangiomas can appear solid, and large hemangiomas can have solid components. When present, calcifications are punctate or curvilinear [45]. Hemangiomas are typically non-encapsulated, with varying portions of capillary and cavernous components. Pure capillary hemangiomas are exceedingly rare. Splenic hemangiomas usually demonstrate early peripheral enhancement and may or may not fill on delayed-phase imaging. Less commonly, splenic hemangioma demonstrates early homogeneous enhancement (Fig. 8.27) [46, 47]. Cavernous hemangiomas often have a more heterogeneous appearance and areas of non-enhancement. The signal intensity on T2-weighted images is usually high, but it may be mildly hyperintense (unlike liver hemangiomas, which are typically markedly hyperintense). Rarely, hemangiomas are seen as large peripherally or heterogeneously enhancing masses that mimic malignancy (as demonstrated above in Fig. 8.26).
Fig. 8.27
Capillary Hemangioma. Axial contrast enhanced CT (a) demonstrates a small well circumscribed homogeneously enhancing lesion along the lateral aspect of the spleen (arrow). Axial contrast enhanced fat suppressed T1-weighted MR image (b) demonstrates an arterially enhancing focus (arrow) with a high signal intensity (arrow) on T2-weighted image (c)
As hemangiomas increase in size, they are prone to rupture and can sequester platelets, resulting in thrombocytopenia. This sequestration, called Kasabach-Merritt syndrome, is more commonly seen with liver hemangiomas. Unless these lesions are symptomatic, treatment is not required. Diffuse involvement of the spleen is seen in hemangiomatosis, which is a rare benign vascular manifestation of systemic angiomatosis (associations with Klippel-Trénaunay-Weber, Turner, Kasabach-Merritt-like, and Beckwith-Wiedemann syndromes have been reported) (Fig. 8.28) or, even less commonly, confined to the spleen. It is sometimes accompanied by a severe disturbance of blood coagulation.
Fig. 8.28
Splenic Hemangiomatosis. Axial contrast enhanced T1-weighted (a) and T2-weighted image (b) show diffuse hemangiomatosis of the spleen (arrows) and chest wall (arrowheads) in a patient with Kasabach-Merritt syndrome
Littoral cell angioma is a vascular neoplasm that is unique to the spleen and is derived from the normal splenic lining of the red pulp (i.e., the littoral cells). It can occur at any age and has no sex predilection. Associations with various malignancies, such as ovarian, pancreatic, and renal cell carcinomas, have been reported [48]. There has also been a reported association with tumor necrosis factor, treatment for sarcoidosis. Littoral cell angioma can be incidentally discovered but presents with fever, splenomegaly, thrombocytopenia, and anemia in up to half of cases.
Two forms of littoral cell angioma have been described, a common multifocal diffuse form (Fig. 8.29) and a less common solitary form (Fig. 8.30) [49]. On CT images, littoral cell angioma presents as multiple small rounded lesions as large as 2 mm [50]. On precontrast imaging, these lesions are hypodense relative to the splenic parenchyma. On delayed imaging, they may enhance homogeneously. The presence of hemosiderin in lesions accounts for the low signal on T1- and T2-weighted images and the blooming artifact on longer TE GRE imaging.
Fig. 8.30
Littoral cell Angioma on MR. Axial T2 weighted (a), axial precontrast T1-weighted (b) and axial contrast enhanced T1-weighted (c) images demonstrate a well circumscribed mass lesion (arrow), exhibiting concentric pattern of hyperintensity on T2-weighted image, low signal intensity on precontrast T1-weighted image with a peripheral (arrow) on post-contrast T1-weighted image
Fig. 8.29
Littoral cell Angioma on CT. Axial nonenhanced CT (a) and axial contrast enhanced CT (b), demonstrate a well circumscribed hypoattenuating lesion (arrow) which exhibits peripheral enhancement
The differential diagnosis of vascular splenic lesions include, in addition to littoral cell angioma, angiosarcoma, hemangioendothelioma, and hemangiopericytoma. Metastatic lesions to the spleen can have similar imaging findings as littoral cell angioma, but metastasis may not demonstrate marked blooming on GRE sequences. Given the broad differential possibilities and particularly in the setting of symptoms, treatment and diagnosis could be only accomplished by splenectomy. The diagnosis of littoral cell angioma should be based on the results of immunohistochemical analysis because these tumors express both vascular antigens (e.g., factor VIII antigen) and histiocytic antigens (e.g., S-100) [50].
FROM：https://radiologykey.com/cross-sectional-imaging-of-the-spleen/
by Khaled M. Elsayes (Editor)
This book offers concise descriptions of cross-sectional imaging studies of the abdomen and pelvis, supplemented with over 1100 high-quality images and discussion of state-of-the-art techniques. It is based on the most common clinical cases encountered in daily practice and uses an algorithmic approach to help radiologists arrive first at a working differential diagnosis and then reach an accurate diagnosis based on imaging features, which incorporate clinical, laboratory, and other underlying contexts.
The book is organized by anatomical organ of origin and each chapter provides a brief anatomical background of the organ under review; explores various cross-sectional imaging techniques and common pathologies; and presents practical algorithms based on frequently encountered imaging features. Special emphasis is placed on the role of computed tomography (CT) and magnetic resonance imaging (MRI). In addition to algorithmic coverage of many pathological entities in various abdominopelvic organs, unique topics are also examined, such as imaging of organ transplant (including kidney, liver and pancreas), evaluation of perianal fistula, and assessment of rectal carcinoma and prostate carcinoma by MRI. Cross-Sectional Imaging of the Abdomen and Pelvis: A Practical Algorithmic Approach is a unique and practical resource for radiologists, fellows, and residents.
Khaled M. Elsayes, MD, is Associate Professor of Diagnostic Radiology at the University of Texas, MD Anderson Cancer Center and University of Texas Medical School, Houston. He formerly served as Assistant Professor at the University of Michigan, Ann Arbor.
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