Answer to case of the month #138. Inflammatory pseudotumour of the spleen

• Published in: Canadian Association of Radiologists journal Vol. 59; no. 4; p. 217
• Main Authors: Sam, Angela, Kirkpatrick, Iain D C
• Format: Journal Article
• Language: English
• Published: United States SAGE PUBLICATIONS, INC 01.10.2008
• Subjects: Biopsy; Contrast Media; Diagnosis, Differential; Female; Flank Pain - etiology; Granuloma, Plasma Cell - diagnosis; Humans; Inflammatory diseases; Middle Aged; Radiographic Image Enhancement - methods; Radiology; Spleen; Spleen - diagnostic imaging; Spleen - surgery; Splenectomy - methods; Splenic Diseases - diagnosis; Tomography, X-Ray Computed - methods; Tumors
• ISSN: 0846-5371; 1488-2361

An IPT of the spleen is a well-circumscribed solitary mass; only infrequently has it been reported as a multinodular lesion. The study by Moriyama et al2 found only 4 cases of splenic IPT described as multiple nodules. It is composed of inflammatory cells-predominantly lymphocytes and plasma cells-in a variable mixture of spindle cells and fibroblastic stroma. Immunohistochemical examination with kappa and lambda light chains shows the polyclonal nature of the plasma cells, in keeping with the benign nature of the lesion.3 The tendency of spindle cell dominance, specifically myofibroblasts, has prompted the suggestion that a more descriptive term for this lesion is inflammatory myofibroblastic tumour.4'5 An IPT forms a bulging yellow or white mass encroaching on the normal splenic parenchyma, with variable degrees of necrosis and hemorrage.6 Splenomegaly (defined as splenic mass greater than 250 g) is often present. In their review of 12 cases of IPT, Neuhauser et al6 reported splenic weights of 140 to 1030 g. To our knowledge, there are no reports of splenic IPT characterized by 18F-FDG PET. There are case reports, however, of a hepatic IPT displaying a SUV^sub max^ 6.7510 and a neck IPT showing a SUV^sub max^ of 8.6. ' ' Metser et al12 found PET quite reliable in discriminating benign and malignant splenic lesions, with the exception of 2 false-positive results (owing to brucellosis and sarcoidosis). These authors suggested that granulomatous disease involving the spleen and noninfectious inflammatory diseases such as IPT, abnormally accumulate 18F-FDG PET and could imitate malignancy. More characterization of IPTs with PET scanning in the future is necessary to appreciate its role in distinguishing these lesions. IPTs of the spleen are most often mistaken for lymphoma, particularly when only one focal lesion is present. Although no lymphadenopathy is noted in the majority of cases of IPT of the spleen, para-aortic lymph node enlargement has been reported in association with this lesion.6 In our patient, enlarged lymph nodes were also noted at multiple sites. Other focal splenic lesions to consider include benign hemangiomas and hamartomas. Both are also often identified incidentally. Features on sonography to help distinguish these from IPT are the presence of cystic components with septations in hemangiomas (unfortunately not always present), and the characteristic homogeneous echogenicity and increased Doppler flow of hamartomas.13 Colour Doppler US of IPT demonstrates a hypovascular mass. 2 Angiosarcoma, although a rare vascular neoplasm, must also be considered as it is the most common nonhematolymphoid tumour of the spleen. Radiologically, it usually presents with irregular margins13 whereas IPT is usually well-defined. Metastatic disease must always be a consideration. However, isolated splenic metastasis is rare and usually occurs in cases of widespread disseminated malignancies.