Primary Splenic Lymphoma Detected by F-18 FDG PET

Multimodality radionuclide imaging in fever of unknown origin presenting with a solitary spleen lesion

Background

Fever of unknown origin (FUO) still represents a serious challenge for clinicians, since it can be related to a wide spectrum of disorders, ranging from infections to malignancies. In this scenario, nuclear medicine can be of value to achieve a correct diagnosis both through positron emission computed tomography (PET/CT) and 99mTc labeled hexamethylpropylene amine oxime (HMPAO) white blood cell (WBC) scintigraphy.

Case presentation

We are presenting the case of 65-year-old male, who was referred to our hospital due to prolonged unexplained fever. He was submitted to abdomen ultrasonography (US) that did not disclose relevant pathological findings. Subsequently, he underwent PET/CT scan with 18F-fluorodeoxyglucose (18F-FDG) that revealed an area of increased tracer uptake in splenic inferior pole. In order to solve differential diagnosis between tumor and infection, he was submitted to 99mTc-HMPAO WBC scintigraphy that resulted negative for sites of pathologic radiolabeled cells’ accumulation but revealed a photopenic area in the splenic inferior pole. The pattern of mismatched uptake between 18F-FDG PET/CT and 99mTc-HMPAO WBC scintigraphy was considered highly suspicious for spleen tumor localization. The patient was scheduled for splenectomy and histology resulted positive for non-Hodgkin lymphoma (NHL) of diffuse large B cell type. After splenectomy, a further 18F-FDG PET/CT revealed the appearance of hypermetabolic hepatic lesions. The patient underwent chemotherapy with complete remission.

Conclusion

Nuclear medicine provides valuable tools for differential diagnosis in FUO. In case of patients presenting solitary lesion of the spleen, the combined use of 18F-FDG PET/CT and 99mTc-HMPAO WBC scintigraphy can provide relevant information to aid clinicians to a correct diagnosis.

Fever of unknown origin revealed to be primary splenic lymphoma: A rare case report with review of the literature

Fever is a common clinical presentation of a number of diseases. A sustained unexplained fever >38.3°C lasting for >3 weeks without an established diagnosis despite intensive diagnostic evaluation is referred to as fever of unknown origin (FUO). FUO remains a clinical challenge for physicians, as it may be attributed to a wide range of disorders, mainly infections, malignancies, non-infectious inflammatory diseases and miscellaneous diseases. We herein report the case of a 59-year-old male patient who presented with prolonged unexplained fever and was found to have a diffusely enlarged hypermetabolic spleen, as shown on ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography examination. Following splenectomy, histopathological examination revealed primary splenic lymphoma (PSL) of B-cell origin. The patient received 6 courses of systemic chemotherapy with rituximab, etoposide, cyclophosphamide, doxorubicin, vincristine and prednisone (R-ECHOP regimen) and responded well to treatment. Thus, in patients with FUO and splenomegaly, the possibility of PSL should be taken into consideration.

FDG PET/CT Findings in Multiple Splenic Amebomas (Amebic Granulomas)

Splenic ameboma (amebic granuloma) is rare. A 38-year-old man with a severe pneumonia due to inhalation of swimming pool water 18 months ago complained of night sweat, tiredness, and anorexia for 1 month. Abdominal ultrasound showed multiple nodules in the spleen. These nodules showed slight enhancement on enhanced CT and intense FDG uptake on PET/CT. Splenectomy was performed. Multiple splenic amebomas were confirmed by pathology. Free-living amoebae were also detected in samples of pleural effusion and blood. Splenic ameboma, although rare, should be included in the differential diagnosis with isolated focally increased FDG activity in the spleen.

Use of 18F-FDG PET/CT imaging for evaluation of patients with primary splenic lymphoma

Primary splenic lymphoma (PSL) is a rare disease, and its management differs from other splenic malignancies. The purpose of the present study was to evaluate the role of 18F-FDG PET/CT in patients with PSL.

METHODS

We retrospectively evaluated the data of 17 patients with PSL (median age, 46 years; range, 3-64) who had undergone 50 18F-FDG PET/CT studies. Of the 50 PET/CTs, 15 were done for primary diagnosis/staging and 35 were done for restaging. PET/CT images were evaluated both qualitatively and quantitatively [maximum standardized uptake value (SUVmax)]. Combination of clinical/imaging follow-up and/or histopathologic diagnosis was taken as reference standard.

RESULTS

Of the total 50 F-FDG PET/CT studies, 27 studies (54%) were positive and 23 (46%) were negative for disease. PET/CT was true positive in 25 studies, true negative in 22 studies, false positive in 2 studies, and false negative in 1 study. Overall, per study-based sensitivity was 96.2%, specificity was 91.7%, and accuracy was 94%. In those studies performed for diagnosis/staging (15/50), PET/CT was true positive in all 15, with an accuracy of 100%. In those studies performed for restaging (35/50), sensitivity was 90.9%, specificity was 91.7%, and accuracy was 91.4%. No significant difference was seen in the accuracy of PET/CT between staging and restaging groups (P=0.601). On 18F-FDG PET/CT, splenic involvement was seen in 24 studies, lymph nodal involvement in 5 studies, liver involvement in 3 studies, and bone marrow involvement in 1 study. More than one site of disease was seen in 9 PET/CT studies. On semiquantitative analysis, the overall mean splenic lesion SUVmax was 6.9±7.9 (median, 4.6; range, 1.3-29). The mean value of ratio of SUVmax of splenic lesions and SUVliver was 4.4±5.5 (median, 2.4; range, 0.9-24.2). On comparison of areas under the curve, the mean value of ratio of SUVmax of splenic lesions and SUVliver was found to be superior to SUVmax alone for this differentiation of involvement from normal spleen (P=0.018).

CONCLUSION

18F-FDG PET/CT seems useful in patients with primary splenic lymphoma and shows high diagnostic accuracy.

Enhanced CT and FDG PET/CT findings of splenic hamartoma

Splenic hamartomas are very rare benign vascular tumors. A 67-year-old man was referred after an incidental detection of a splenic lesion. Abdominal-enhanced CT showed a splenic lesion with progressive enhancement. This lesion showed intense FDG uptake with an SUVmax of 9.2. The patient underwent splenectomy. Splenic hamartoma was confirmed by pathologic evaluation. In this tumor, the disorganized splenic sinus contained a large amount of lymphocytes and plasma cells, which may contribute to the intense FDG uptake. This case indicates that splenic hamartoma should be included in the differential diagnosis of focal FDG accumulation along with tumor and nontumor conditions.

Imaging of extranodal lymphoma with PET/CT

Hodgkin disease (HD) and non-Hodgkin lymphoma (NHL) represent a spectrum of malignant neoplasms arising from the lymphoid system with an incidence of around 8% of all malignancies. Although they are generally known as tumors of lymph nodes, 25% to 40% of HD/NHL tumors, especially NHL, arise at extranodal sites along the gastrointestinal tract, head and neck, orbit, central and peripheral nervous system, thorax, bone, skin, breast, testis, thyroid, and genitourinary tract. Extranodal involvement is an important pretreatment prognostic factor for patients with lymphoma and its incidence has increased in the past 2 decades. Imaging plays an important role in the noninvasive pretreatment assessment of patients with extranodal lymphoma. This involvement can be subtle and may be overlooked during computed tomography (CT). Positron emission tomography/CT (PET/CT) has evolved into an important imaging tool for evaluation of lymphomas, facilitating the detection of affected extranodal sites even when CT shows subtle or no obvious lesions. Familiarity with extranodal manifestations and suggestive PET/CT features in different sites is important for accurate evaluation of lymphoma. This article reviews the extranodal PET/CT imaging findings regarding HD and NHL.

Non-Hodgkin's lymphoma of the bone and the liver without lymphadenopathy revealed on FDG-PET/CT

Primary extranodal lymphomas are much less frequent than nodal lymphomas. Osseous and hepatic lymphomas commonly present with additional nodal lesions. Primary lymphoma of the bone or of the liver without nodal disease is uncommon. We describe a case of extranodal non-Hodgkin's lymphoma with numerous osseous and hepatic lesions without any lymph node involvement on FDG-PET/CT images. This is the first report of the coexistence of both osseous and hepatic lymphoma in the same patient without any lymph node involvement.