Enhanced CT and FDG PET/CT in Histiocytic Sarcoma of the Pericardium

FDG PET/CT Imaging of Liver and Spleen Histiocytic Sarcoma

ABSTRACT

Histiocytic sarcoma is a tumor of the lymphohematopoietic system characterized by macrophage morphology and immunophenotype. Here, we report FDG PET/CT images of a 50-year-old man with coexisting histiocytic sarcoma of the liver and spleen. Images showed multiple enhanced uptake lesions of FDG in both the liver and spleen. Ultimately, histiocytic sarcoma was confirmed by the biopsy histopathology.

Enhanced Computed Tomography and 18F-fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in the Uncommon Histiocytic Sarcoma of Small Intestine Arising after Gastric Large B-Cell Lymphoma

Histiocytic sarcoma (HS) is an extremely rare and aggressive malignant neoplasm of hematopoietic origin that shows morphologic and immunophenotypic evidence of histiocytic differentiation. In approximately 25% of the cases, presumed transdifferentiation of a preexisting hematolymphoid disorder can be demonstrated. Various extranodal sites, particularly the gastrointestinal tract, soft tissue, skin, and spleen, can be involved. Enhanced CT and FDG PET/CT findings of extranodal histiocytic sarcoma have been barely reported. We present a case with extranodal HS originating in the small intestine after gastric large B-cell lymphoma, mistaken for prostate cancer metastasis in a 76-year-old man.

Periarticular histiocytic sarcoma with heart metastasis in a cat

A 4-year-old intact female domestic short-haired cat was referred for recommendations about adjuvant medical treatment 1 month after left forelimb amputation due to periarticular histiocytic sarcoma (HS). At presentation, physical abnormalities were limited to enlarged ipsilateral superficial cervical and axillary lymph nodes. Routine blood analysis, abdominal ultrasound, and thoracic radiology were unremarkable. The cat initially received lomustine without any adverse events. Four weeks later, the cat developed severe acute respiratory distress. Results of thoracic radiographs and transthoracic echocardiographic analysis were suggestive of pulmonary and heart metastasis. Due to the cat's poor clinical condition and prognosis, the owner elected euthanasia, and a necropsy was performed. Based on gross pathology, histopathology, and immunohistochemistry, an HS with nodal, renal, pulmonary, and heart (right auricular and right ventricular) metastases was diagnosed. This case represents the first description of HS with a heart metastasis in a cat, providing further insight into the clinical course and metastatic behavior of this rare malignant neoplasm. Clinicians should be aware of this site of metastasis and consider HS in the list of differential diagnoses for secondary heart tumors in cats.

New onset headache caused by histiocytic sarcoma of the spinal cord and leptomeninges: a case report

Background

Headache due to raised intracranial pressure is rarely caused by spinal lesions. We describe a patient with primary histiocytic sarcoma who presented with a new onset headache with features of raised intracranial pressure and subtle signs of cauda equina syndrome due to predominant lower spinal cord infiltration and minimal intracranial involvement.

Case

A previously well 54-year-old man presented with a 2-month history of new onset headache with features of raised intracranial pressure. Progression of lower limb weakness was delayed and mild with diagnostic delay resulting from the primary presentation with headache leading to an initial focus on cerebral pathology. Subsequent investigations revealed a previously unreported presentation of primary histiocytic sarcoma infiltrating the cauda equina causing raised intracranial pressure headache.

Conclusion

This case highlights the importance of a broad search in the investigation of new onset raised intracranial pressure headache, including imaging of the lower spinal cord. Primary histiocytic sarcoma should be considered in the differential diagnosis of this rare syndrome.

Histiocytosis and Neoplasms of Macrophage-Dendritic Cell Lineages: Multimodality Imaging with Emphasis on PET/CT

Histiocytosis is a rare inflammatory process characterized by pathologic infiltration and accumulation of cells derived from the monocytic lineage in normal tissue. It encompasses more than 100 different subtypes of disorders that were recently classified into five main groups: (a) Langerhans-related histiocytosis, (b) Rosai-Dorfman histiocytosis, (c) cutaneous and mucocutaneous histiocytosis, (d) malignant histiocytosis, and (e) hemophagocytic lymphohistiocytosis and macrophage activation syndrome. Langerhans cell histiocytosis is the most common histiocytic disorder. Less common types include Erdheim-Chester disease, Rosai-Dorfman disease, adult and juvenile xanthogranuloma, necrobiotic xanthogranuloma, histiocytic sarcoma, interdigitating dendritic cell sarcoma, Langerhans cell sarcoma, and hemophagocytic lymphohistiocytosis. Although the pathogenesis of these disorders may be attributable to mutations in the oncogenic driver, recent discoveries have shown that inflammation and fibrosis secondary to mutated histiocytes, rather than a proliferative cell mechanism, result in manifestation of the disease. Diagnosis, which relies on a multidisciplinary approach, is challenging and often delayed because clinical findings are nonspecific and may mimic malignant processes at radiologic evaluation. Compared with conventional imaging, PET/CT allows detection of the increased metabolic activity in histiocytes. Diagnostic algorithms for histiocytic disorders should include functional imaging with fluorine 18 (¹⁸F) fluorodeoxyglucose (FDG) PET/CT, which provides a comprehensive whole-body evaluation of their potential involvement with multiple organ systems and allows monitoring of therapeutic response. The most recent revised classification, pathophysiologic and clinical manifestations, sites of involvement, and imaging features of histiocytosis are described in this review and a multimodality approach is used, with emphasis on ¹⁸F-FDG PET/CT evaluation. ^©RSNA, 2021.

Mediastinal Masses: 18F-FDG-PET/CT Features Based on the International Thymic Malignancy Interest Group Classification

Imaging plays a key role in the management of mediastinal masses. In an effort to standardize the analysis of the mediastinum, the International Thymic Malignancy Interest Group (ITMIG) has proposed a three compartments-based diagnostic classification, intended for clinicians and radiologists. Several articles have documented its usefulness to guide the diagnosis using cross-sectional imaging. Similarly, fluorine-18-radiolabeled fluorodeoxyglucose positron emission tomography combined to computed tomography (¹⁸F-FDG-PET/CT) can be useful in this setting, either as a first-line diagnostic technique, or in addition to cross-sectional imaging. In this article, which is thought as an aid for nuclear medicine physicians and radiologists, we aim to present, based on the ITMIG classification, the main mediastinal pathologies that can be observed with ¹⁸F-FDG-PET/CT, and the additional diagnostic value that can be expected from this technique. For this purpose, we segmented the mediastinum according to the ITMIG classification, and reviewed the available literature for each of the corresponding organs and/or disease. Given the importance of the clinical context for the interpretation of PET imaging, we presented each of the diseases according to: (1) their suggestive clinical context; (2) the suggestive features on nonenhanced CT (which is the standard in PET imaging); and (3) the typical ¹⁸F-FDG characteristics. The purpose of this article is to depict the main features of the most common mediastinal diseases that can be encountered with ¹⁸F-FDG-PET/CT, and to highlight its diagnostic value in this setting, alone or in combination with other imaging modalities.

Primary Pericardial Angiosarcoma Shown on FDG PET/CT

A 63-year-old woman had persistent bloody pericardial effusion. Tuberculous pericarditis was initially suspected, but empirical antituberculosis therapy was futile. FDG PET/CT study revealed abnormal FDG activity in multiple parts of the pericardium, especially along with aorta and main pulmonary artery, and in the left atrium. However, there was no abnormal activity in other parts of the body. Histopathologic examination revealed primary pericardial angiosarcoma.