Faculty Bibliography

There is a wide pathological spectrum of kidney sarcomas that show characteristic histology, ontogeny, and clinical-biological behavior. While leiomyosarcomas commonly arise from the capsule, solitary fibrous tumors and clear cell sarcomas typically show renal sinus and medullary epicenter, respectively. Although distribution and imaging findings of some sarcomas may be characteristic, definitive diagnosis warrants histopathological examination following surgery. Renal sarcomas manifest advanced disease at presentation and portend poor prognosis.

Ovarian epithelial carcinoma (OEC), the most common ovarian malignancy, is a heterogeneous disease with several histologic subtypes that show characteristic cytogenetic features, molecular signatures, oncologic signaling pathways, and clinical-biologic behavior. Recent advances in histopathology and cytogenetics have provided insights into pathophysiologic features and natural history of OECs. Several studies have shown that high- or low-grade serous, endometrioid, and clear cell carcinomas are characterized by mutations involving the TP53, K-ras/BRAF, CTNNB1, and PIK3CA genes, respectively. High-grade serous carcinomas, the most common subtype, often manifest with early transcoelomic spread of disease beyond the ovaries, whereas low-grade serous and mucinous carcinomas commonly manifest with early-stage disease, with a resultant excellent prognosis. On the basis of pathogenetic mechanisms, recent findings suggest a dualistic model of ovarian carcinogenesis consisting of types I and II. Type I (low-grade serous, mucinous, and endometrioid) cancers commonly arise from well-described, genetically stable precursor lesions (usually borderline tumors); manifest as large adnexal masses with early-stage disease; and have a relatively indolent clinical course, with an overall good prognosis. In contrast, type II carcinomas (high-grade serous, endometrioid, mixed, and undifferentiated variants) originate de novo from the adnexal epithelia, often demonstrate chromosomal instability, and have aggressive biologic behavior. Better knowledge of hereditary ovarian cancer syndromes and associated cytogenetic abnormalities has led to increased interest in novel biomarkers and molecular therapeutics. Genetic changes, pathologic features, imaging findings, and natural histories of a variety of histologic subtypes of OEC are discussed in this article.

Solitary fibrous tumors (SFTs) are a unique group of mesenchymal neoplasms of fibroblastic or myofibroblastic origin. These tumors were originally described as "benign fibrous mesotheliomas" of the pleural cavity and were erroneously thought to be confined to the serosal surfaces (due to a putative mesothelial or submesothelial origin). It is now established that SFTs are ubiquitous neoplasms with both pleural and extrapleural distribution. Extrapleural SFTs commonly occur in middle-aged adults and manifest as asymptomatic, slow-growing, large tumors. Fewer than 5% of patients with SFTs present with symptomatic hypoglycemia. SFTs are histopathologically diverse with a variable admixture of fibroblasts or myofibroblasts, numerous thin-walled vessels, and dense fibrosis. Tumors previously categorized as hemangiopericytomas are now considered cellular variants of SFTs. At imaging, SFTs demonstrate remarkable heterogeneity, with variable degrees of enhancement, necrosis, or hemorrhage. Although most extrapleural SFTs have a benign clinical course, 10%-15% of these tumors demonstrate aggressive behavior in the form of recurrence or malignancy.

Focal nodular hyperplasia (FNH), hepatocellular adenoma (HCA), and hepatocellular carcinoma (HCC) compose hepatocellular neoplasms that occur in adults. These tumors demonstrate characteristic epidemiologic and histopathologic features and clinical and imaging manifestations. HCAs are monoclonal neoplasms characterized by increased predilection to hemorrhage or rupture and occasional transformation to HCC. On the other hand, FNH is a polyclonal tumorlike lesion that occurs in response to increased perfusion and has an indolent clinical course. Up to 90% of HCCs occur in the setting of cirrhosis. Chronic viral hepatitis (hepatitis B and hepatitis C) infection and metabolic syndrome are major risk factors that can induce HCCs in nonfibrotic liver. Recent advances in pathology and genetics have led to better understanding of the histogenesis, natural history, and molecular events that determine specific oncologic pathways used by these neoplasms. HCAs are now believed to result from specific genetic mutations involving TCF1 (transcription factor 1 gene), IL6ST (interleukin 6 signal transducer gene), and CTNNB1 (beta catenin-1 gene); FNHs are characterized by an "imbalance" of angiopoietin. While the beta catenin signaling pathway is associated with well- and moderately differentiated HCCs, mutations involving p53 (tumor protein 53 gene), MMP14 (matrix metalloproteinase 14 gene), and RhoC (Ras homolog gene family, member C) are associated with larger tumor size, higher tumor grade with resultant shortened tumor-free survival, and poor prognosis. Fibrolamellar carcinoma (FLC), a unique HCC subtype, exhibits genomic homogeneity that partly explains its better overall prognosis. On the basis of recent study results involving cytogenetics and oncologic pathways of HCCs, novel drugs that act against molecular targets are being developed. Indeed, sorafenib (a multikinase inhibitor) is currently being used in the successful treatment of patients with advanced HCC. Characterization of genetic abnormalities and genotype-phenotype correlations in adult hepatocellular tumors provides better understanding of tumor pathology and biology, imaging findings, prognosis, and response to molecular therapeutics.

Hepatocellular adenomas (HCAs) are uncommon, benign hepatocellular neoplasms that commonly occur in young women. Recent advances in pathology and cytogenetics have thrown fresh light on the pathogenesis of HCAs leading to classification of HCAs into 3 distinct subtypes, each with a characteristic epidemiology, histopathology, oncogenesis, and imaging findings. The aim of the article was to provide a comprehensive review of contemporary taxonomy of HCAs, with an emphasis on cross-sectional imaging findings and management.

Renal cystic diseases in adults are a heterogeneous group of disorders characterized by the presence of multiple cysts in the kidneys. These diseases may be categorized as hereditary, acquired, or developmental on the basis of their pathogenesis. Hereditary conditions include autosomal dominant polycystic kidney disease, medullary cystic kidney disease, von Hippel-Lindau disease, and tuberous sclerosis. Acquired conditions include cystic kidney disease, which develops in patients with end-stage renal disease. Developmental cystic diseases of the adult kidney include localized renal cystic disease, multicystic dysplastic kidney, and medullary sponge kidney. In recent years, many molecular and cellular mechanisms involved in the pathogenesis of renal cystic diseases have been identified. Hereditary renal cystic diseases are characterized by genetic mutations that lead to defects in the structure and function of the primary cilia of renal tubular epithelial cells, abnormal proliferation of tubular epithelium, and increased fluid secretion, all of which ultimately result in the development of renal cysts. A better understanding of these pathophysiologic mechanisms is now providing the basis for the development of more targeted therapeutic drugs for some of these disorders. Cross-sectional imaging provides useful information for diagnosis, surveillance, prognostication, and evaluation of treatment response in renal cystic diseases.

There is a heterogeneous group of noninfectious gastroenterocolitis syndromes that are characterized by immune dysregulation. Recent advances in pathologic analysis have allowed for better characterization of many of these disorders. Some entities demonstrate characteristic disease distribution, epidemiologic features, natural history, and response to specific therapy. For instance, celiac disease occurs in genetically susceptible individuals who are sensitive to gluten, eosinophilic esophagitis is an immune response to ingested allergens, and microscopic colitis predominantly occurs in older patients with chronic diarrhea and is induced or exacerbated by drugs. Eosinophilic gastroenteritis has a variety of clinical and imaging manifestations. Crohn disease and ulcerative colitis are multifactorial immune-mediated chronic inflammatory disorders and have become increasingly prevalent in recent years. Multidetector computed tomography and magnetic resonance imaging provide valuable information that may be used to diagnose these conditions, guide treatment, and assess changes after treatment, and the role of imaging in evaluating response to therapy continues to evolve and expand.

OBJECTIVE: The purpose of this review is to describe the epidemiologic, etiopathogenetic, clinical, and imaging characteristics of various nonalcoholic, nonbiliary pancreatitis syndromes. CONCLUSION: The spectrum of nonalcoholic, nonbiliary pancreatitis includes autoimmune pancreatitis, groove pancreatitis, hereditary pancreatitis, tropical pancreatitis, tuberculous pancreatitis, and metabolic pancreatitis. Advances in genetics and molecular pathology have shed new light on the etiopathogenesis and course of these syndromes. Accurate diagnosis aided by imaging findings allows optimal management.

Quantification of tumor burden and assessment of changes in tumor size after chemotherapy are commonly performed to evaluate treatment response in oncology trials. Validation and adoption of different criteria have been attempted in the past to achieve uniformity in scanning techniques and measurement metrics so that comparison of different oncological trials is feasible. Response assessment of solid tumors is usually consisted of either bidimensional (World Health Organization criteria) or unidimensional (Response Evaluation Criteria in Solid Tumors [RECIST] guidelines) measurement of tumors before and after chemotherapy. RECIST 1.1 criteria have been recently published. In this article, we try to provide a comprehensive review of the tumor response evaluation guidelines that were recently updated in attempts to overcome limitations of the previous criteria as well as incorporate recent advances in imaging techniques.