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Encapsulated fat necrosis is a degenerative process involving various mature adipose tissues. We report on a case of abdominal encapsulated fat necrosis which mimicked abdominal liposarcoma, and we discuss its imaging findings on computed tomography (CT).
Magnetic resonance imaging was performed in eight children with abdominal neuroblastomas. Five patients had serial examinations after diagnosis, and 15 computed tomography (CT) scans were available for comparison. MR imaging was as precise as CT in detecting the presence or absence of liver involvement and more efficient in determining the relationship of tumor to vascular structures. However, it did not differentiate tumor from normal kidney as accurately as CT. Inversion recovery (IR) images yielded the greatest soft-tissue contrast resolution between liver and tumor. T1 values of tumor were much higher than those of normal liver but overlapped those of normal kidneys. T2 values of tumor were significantly higher than those of the liver and were slightly, but not significantly, lower than those of the kidneys. Either T1- or T2- weighted pulse sequences should, therefore, provide adequate liver-tumor differentiation, but more heavily T2- weighted images appear necessary to distinguish between tumor and kidney. T1 values of tumors usually decreased with rapid tumor regression, while T2 values changed independently. The ability to quantitate tissue parameters helps in selecting appropriate imaging sequences and may be of use in following the progress of tumors.
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Ectomesenchymomas (EM) are rare malignant neoplasms usually consisting of rhabdomyosarcoma (RMS) with a neural component. Only 21 cases have been previously reported. Here we extend the clinicopathologic spectrum of EM by describing our findings in 15 cases. Only 5 patients were infants; 10 were < or =3 years old and 5 were > or =6 years old. No male predilection was observed; 7 were female. The originating institutional diagnoses were; RMS (12), undifferentiated sarcoma (1), or EM (2), suggesting underdiagnosis of this entity. The primary tumor sites included external genital (5), pelvis/abdomen (6), head and neck (3), and extremity (1). The size of the primary neoplasm was usually > or =5 cm at diagnosis but dissemination only occurred in a minority. Local infiltration was not uncommon. These neoplasms were typically multilobate, thinly encapsulated, hemorrhagic, and necrotic. Light microscopic features were highly variable, but embryonal RMS with scattered or clustered ganglion cells, often in lacunae, was characteristic. In some cases, primitive neuroblastic or neuroectodermal areas were found and/or a component of alveolar RMS was seen. Focal anaplasia was occasionally observed. Mitotic activity appears higher than previously appreciated and some necrosis was invariably present. Electron microscopy was performed in 11 cases, which confirmed skeletal muscle +/- neural differentiation. Cytogenetic studies performed in five cases revealed no specific abnormality. Monoclonal neuron-specific enolase was the best marker of ganglion cells and primitive neural elements. MIC-2 (CD99) membrane expression was not definitively present in any of the six cases examined. A number of the above parameters appear to be of some prognostic significance, but overall, these neoplasms appear to have a similar outcome as would be predicted for their RMS element alone (exclusive of any neural component), with respect to the RMS subtype, age of the patient, and anatomic location of the neoplasm.
Thymoma is associated with benign and neoplastic diseases. The authors report the concurrence of invasive thymoma and T-lymphoblastic leukemia/lymphoma in a 95-year-old man. The hematologic malignancy was suspected terminally, whereas the thymoma was discovered at necropsy. The lymphoblastic leukemia/lymphoma had a clonally rearranged T-cell receptor beta-chain gene and a mature thymocyte immunophenotype. No retroviral gene sequences (human immunodeficiency virus 1 and 2, and human T-cell leukemia virus 1 and 2) were identified by polymerase chain reaction and hybridization analysis. The association of thymoma with hematologic neoplasm is reviewed.
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A patient is described who initially presented with pemphigus vulgaris, limited to the oral cavity, and weight loss. Although the various laboratory studies pointed to the diagnosis of paraneoplastic pemphigus (PNP), the underlying neoplasm was not detected until 6 months later, when the patient developed shortness of breath and routine physical examination on admission revealed an abdominal mass, which eventually was proven to be an epithelioid leiomyosarcoma. In spite of radical excision of the tumour and intensive treatment of the dyspnoea, the patient died of respiratory failure 19 months after the PNP had been diagnosed. Early diagnosis of PNP is stressed to possibly prevent fatal pulmonary involvement.
Benign urachal neoplasms have been rarely reported. We describe a case of a large benign mesenchymal neoplasm (21 x 19 x 14 cm) arising from the urachus, with imaging by computed tomography and ultrasound.
Stage-adapted treatment in oncology relies on correct tumor staging for patients with malignant diseases. To ensure accurate assessment of the tumor stage in thoracic and abdominal diseases by PET/CT, both CT and PET need to be optimized. In this setting, different malignant diseases require customized imaging protocols. Although in the clinical setting of therapy assessment, PET/CT with integration of low-dose, nonenhanced CT may be sufficient, tumor staging may require a more sophisticated CT protocol. This review focuses on potential CT protocols for imaging cancers of the chest and abdomen. Examples of CT protocols are presented and discussed for non-small cell lung cancer, breast cancer, colorectal cancer, gastrointestinal stromal tumors, and interventional liver therapy.
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Carcinoid tumors are rare neuroendocrine neoplasms that belong to a more general category of tumor called the APUDomas. Ninety percent of carcinoid tumors are located in the gastrointestinal tract. Abdominal carcinoid tumors are categorized according to the division of the primitive gut from which they arise. Carcinoid tumors originating from the foregut develop in the gastric wall, duodenum, and pancreas; those originating from the midgut develop from the small bowel, appendix, and right colon; and those originating from the hindgut develop from the transverse or left colon or from the rectum. This report illustrates the computed tomographic appearance of primary and metastatic carcinoid tumors of the abdomen. Among the different organs that may be involved by metastases from carcinoid tumor, special emphasis is placed on the liver.
CT diagnosis of intraabdominal abscess was confirmed in 18 patients by laparatomy and in two by autopsy. In CT abscess is characterized by an expansive soft-tissue lesion with different density values, mostly with a central fluid collection and a thickened wall. The peripheral inflammatory reaction leads to obliteration of fat planes surrounding the adjacent organs. Further symptoms are contrast enhancement of the wall and extraluminal gas collection. The combination of all these signs together with a suitable history and clinical findings allow a reliable diagnosis of abscess formation. When only isolated signs are found, differentiation from tumor, pseudocyst or hematoma may be difficult.
The existence of extrarenal rhabdoid tumor (ERRT) as a discrete pathologic entity has been controversial despite frequent reports of its occurrence. We performed immunohistochemistry, electron microscopy, or both on 42 cases with this diagnosis sent in consultation to us. Only 12 of the 42 neoplasms had the histological findings of "classic" malignant rhabdoid tumor of the kidney; the remainder displayed a variety of neural, epithelial, myoid, mesenchymal, or ependymal patterns. Electron microscopy also showed that most possessed neural, epithelial, or ependymal features. Immunohistochemistry generally revealed marked polyphenotypia, with immunoreactivity to a wide array of antibodies against neural, epithelial, glial, and myogenic markers. A specific tissue-based diagnostic category could not be assigned in only 11 of the 42 cases, seven of which lacked material for a comprehensive ultrastructural or immunohistochemical study. We conclude that tumors currently diagnosed as ERRT represent a heterogeneous group of neoplasms that may form unique subsets of known entities within the specific site where they arise or that may defy classification into a specific alternative category. Our findings lead us to believe that the term ERRT is not valid as representing a specific diagnostic entity and to prefer the term "poorly differentiated neoplasm with rhabdoid features" for undifferentiated tumors.
PURPOSE: To compare image quality, diagnostic acceptability, and radiation exposure associated with 16-section multi-detector row computed tomographic (CT) examinations of abdomen and pelvis performed with z-axis modulation technique of automatic tube current modulation and with manual selection of fixed tube current. MATERIALS AND METHODS: Sixty-two consecutive subjects (mean age, 60 years; age range, 19-84 years; male-to-female ratio, 35:27) underwent follow-up CT of abdomen and pelvis with use of a 16-section multi-detector row scanner and z-axis modulation technique (10.5-12.0-HU noise index, 10-380 mA). Scanning parameters included 140 kVp, 0.5-1.0-second gantry rotation time, 0.938:1 beam pitch, and 5-mm reconstructed section thickness. For each subject, images obtained with z-axis modulation were compared with previous images obtained with fixed tube current (200-300 mA) and with other parameters identical. Images were compared for noise and diagnostic acceptability by two subspecialty radiologists using a five-point scale (1, unacceptable; 3, acceptable; 5, excellent) at five levels: upper liver at diaphragm, porta hepatis, right kidney hilum, iliac crest, and upper margin of acetabulum. Tube current and gantry rotation time used for acquisitions at these levels were recorded. Data were analyzed with parametric and nonparametric statistical tests. RESULTS: Although no significant differences were found (P =.34), images acquired with z-axis modulation at the levels of the upper liver (diaphragm) and acetabulum had a higher noise and lower diagnostic quality, compared with images acquired with fixed tube current. Compared with fixed tube current, z-axis modulation resulted in tube current-time product reduction in 54 (87%) of 62 examinations (mean reduction, 71.2 mAs) and increase in eight (13%) (mean increase, 17.0 mAs). CONCLUSION: Compared with manually selected fixed tube current, z-axis automatic tube current modulation resulted in reduced tube current-time product and similar image noise and diagnostic acceptability at CT of abdomen and pelvis.
Acquired immunodeficiency syndrome (AIDS) is a lethal infectious disease that has reached epidemic proportions in urban centers of the United States. Intraabdominal opportunistic infections and malignancies are common features of this syndrome. A prodromal phase or possibly milder form of infection is known as the AIDS-related complex. Abdominal computed tomography (CT) in patients with AIDS-related complex often demonstrates a triad of mild retroperitoneal and mesenteric adenopathy, splenomegaly, and perirectal inflammation. Lymph node enlargement greater than 1.5 cm is unusual in the AIDS-related complex and should prompt CT-guided biopsy. Abdominal adenopathy (greater than 1.5 cm) in AIDS, in our experience, is most commonly related to non-Hodgkin lymphoma, Kaposi sarcoma, or infection with Mycobacterium avium-intracellulare. In most instances, CT-guided biopsy with appropriate staining technique can readily distinguish these entities. However, the subtyping of non-Hodgkin lymphoma by fine-needle aspiration biopsy alone remains controversial. Unusual features of abdominal malignancies are common in AIDS. These include a purely lymphadenopathic form of AIDS-related Kaposi sarcoma and a predilection for extranodal sites of lymphoma in AIDS. In general, patients with AIDS-related lymphoma present with advanced stages of disease with highly malignant histologic subtypes. Abdominal CT may be useful clinically for diagnosing intraabdominal complications of AIDS.
OBJECTIVE: Non-Hodgkin's lymphoma is a common complication in patients with HIV infection. The purpose of this study was to analyze the abdominal CT findings in a large series of patients with this condition. MATERIALS AND METHODS: We retrospectively reviewed the abdominal CT examinations of 110 men and two women (21-62 years old; average, 39 years) with untreated AIDS-related lymphoma, as defined by the Centers for Disease Control. Lymphoma was the initial AIDS-defining illness in 79% of the patients. RESULTS: Abdominal CT scans showed normal findings or only mild enlargement of the liver or spleen in 36% of the 112 patients, whereas evidence of intraabdominal lymphoma was seen in 64%. Evidence of focal lymphomatous involvement was seen on abdominal CT scans in 58 (98%) of 59 patients in whom the predominant signs and symptoms were related to the abdomen and in 14 (26%) of 53 patients with extraabdominal signs or symptoms. In the 64% of patients with evidence of intraabdominal lymphoma, lymph node enlargement was seen in 56% and extranodal disease was seen in 86%. Extranodal sites of involvement in the 72 patients with evidence of intraabdominal lymphoma included the gastrointestinal tract (54%), liver (29%), kidney (11%), adrenal gland (11%), lower genitourinary tract (10%), spleen (7%), peritoneum and omentum (7%), pancreas (5%), epidural space (4%), bone (3%), and muscle (1%). Mild enlargement of the liver or spleen was present in a minority of cases. Moderate or marked hepatomegaly (cephalocaudal span > 20 cm) and splenomegaly (cephalocaudal span > 15 cm) were even less common and occurred only in the presence of focal hepatic lesions. CONCLUSION: Our results show that AIDS-related lymphoma may affect any abdominal organ, most commonly lymph nodes, the gastrointestinal tract, liver, kidney, and adrenal gland. Hepatic or splenic enlargement was uncommon and was not often seen as an isolated finding in the absence of evidence of abdominal lymphoma.
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