MRI of the Lactating Breast.

The breasts undergo marked physiologic changes during lactation that can make conventional imaging evaluation with mammography and US challenging. MRI can be a valuable diagnostic aid to differentiate physiologic and benign processes from malignancy in patients who are lactating. In addition, MRI may allow more accurate delineation of disease involvement than does conventional imaging and assists in locoregional staging, screening of the contralateral breast, assessment of response to neoadjuvant chemotherapy, and surgical planning. Although the American College of Radiology recommends against patients undergoing contrast-enhanced MRI during pregnancy because of fetal safety concerns, contrast-enhanced MRI is safe during lactation. As more women delay childbearing, the incidence of pregnancy-associated breast cancer (PABC) and breast cancer in lactating women beyond the 1st year after pregnancy is increasing. Thus, MRI is increasingly being performed in lactating women for diagnostic evaluation and screening of patients at high risk. PABC is associated with a worse prognosis than that of non-PABCs, with delays in diagnosis contributing to an increased likelihood of advanced-stage disease at diagnosis. Familiarity with the MRI features of the lactating breast and the appearance of various pathologic conditions is essential to avoid diagnostic pitfalls and prevent delays in cancer diagnosis and treatment. The authors review clinical indications for breast MRI during lactation, describe characteristic features of the lactating breast at MRI, and compare MRI features of a spectrum of benign and malignant breast abnormalities. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material. See the invited commentary by Chikarmane in this issue.

Repeated sinus CT imaging after recent head imaging.

OBJECTIVES: Excessive use of sinus CT is a significant problem in medical imaging, resulting in unnecessary costs and radiation exposure. This study assesses frequency of sinus CT performed after recent head imaging has already adequately evaluated the sinuses. METHODS: A retrospective search of the PACS database of an academic medical center was performed to identify cases of sinus CT imaging in 2017. Cases were excluded if sinus CT was performed related to trauma, tumor, operative evaluation, or acute infection other than sinusitis (orbital cellulitis, intracranial abscess). Studies with separate imaging covering the sinuses ordered at the same time as sinus CT or performed previously within 4 weeks were identified and clinical information was recorded. RESULTS: Of 735 sinus CTs performed, 19 (5%) had same-day head imaging and 30 (8%) had previous head imaging within 4 weeks, adding up to a cumulative 13% of cases with recent head imaging. The average patient age was 42, with 13 pediatric cases. Of ordering providers, residents ordered the highest percentage of sinus CTs with same-day head imaging (84%) and previous imaging within 4 weeks (63%). The sinuses were described in all head CT radiology reports, while 10 of 12 brain MRI reports did not mention the sinuses. CONCLUSION: In one year, 13% of patients receiving sinus CTs at our institution had recent head imaging. A focused education effort for ordering providers to avoid repeating sinus imaging, and for radiology to comment on sinuses on head imaging, may reduce unnecessary sinus CTs.

A systematic review of shunt-related extraneural metastases of primary central nervous system tumors.

Extraneural metastasis (ENM) of primary central nervous system (CNS) tumors is an uncommon occurrence. Case reports and case series describe ENM after shunting, but this phenomenon has not been well characterized. In this review we aim to better understand the risk factors and clinical implications of ENM associated with shunting. A literature search of cases of ENM related to shunt placement in patients with primary CNS tumors reported through January 2018 was performed using PubMed and Google Scholar. We identified 106 cases of ENM of primary CNS tumors related to shunt placement. The three most common tumor histologies resulting in ENM were germinoma (24%), medulloblastoma (21%), and glioblastoma (11%). Of the patients with ENM, 48% had leptomeningeal spread and 37% had brain or spinal cord metastasis. Mean survival time from shunt placement was 13 months. Ventriculoatrial-shunted cases had higher rates of widespread metastasis and shorter average survival time from shunt placement (2 months) than the average of all types of shunts. Given the known association with ENM, careful consideration should be given to shunt placement in patients with primary CNS tumors, especially germinomas, medulloblastomas, and glioblastomas. Appropriate surveillance should be instituted after shunt placement, and leptomeningeal or neural metastasis should prompt the consideration of potential ENM. When considering distal shunt options, our review suggests that ventriculoatrial shunts should be avoided if possible. For truly obstructive pathologies, the risk of ENM is a further indication to consider other treatment options such as endoscopic third ventriculostomy rather than shunt placement.

Pyruvate kinase isoform expression alters nucleotide synthesis to impact cell proliferation.

Metabolic regulation influences cell proliferation. The influence of pyruvate kinase isoforms on tumor cells has been extensively studied, but whether PKM2 is required for normal cell proliferation is unknown. We examine how PKM2 deletion affects proliferation and metabolism in nontransformed, nonimmortalized PKM2-expressing primary cells. We find that deletion of PKM2 in primary cells results in PKM1 expression and proliferation arrest. PKM1 expression, rather than PKM2 loss, is responsible for this effect, and proliferation arrest cannot be explained by cell differentiation, senescence, death, changes in gene expression, or prevention of cell growth. Instead, PKM1 expression impairs nucleotide production and the ability to synthesize DNA and progress through the cell cycle. Nucleotide biosynthesis is limiting, as proliferation arrest is characterized by severe thymidine depletion, and supplying exogenous thymine rescues both nucleotide levels and cell proliferation. Thus, PKM1 expression promotes a metabolic state that is unable to support DNA synthesis.