It has been more than 30 years since the Bosniak classification of cystic renal masses was first proposed (1). This CT-based classification was introduced in 1986 and originally divided cystic renal masses into one of four classes after exclusion of infectious, inflammatory, and vascular etiologies (Table 1) (1). Since then, refinements have reduced the number of benign masses in Bosniak class III (2-9). For example, Bosniak IIF (where the F is for follow-up) was added for cystic masses with many thin (or minimally thickened) septa with "perceived" enhancement, large (.3 cm) homogeneous nonenhancing hyperattenuating masses, and masses with thick or non-border-forming calcification.Bosniak summarized these changes in 2012 and contended that Bosniak I and II masses were "clearly benign," Bosniak IV masses were "clearly malignant," Bosniak IIF masses were "probably benign," and Bosniak III masses were "indeterminate" (approximately half were malignant and half were not) (9). These adaptations enabled radiologists and urologists to render specific management recommendations: Bosniak I and II masses have been ignored, Bosniak IIF masses have been followed, and Bosniak III and IV masses historically have been treated unless substantial comorbidities or limited life expectancy would warrant observation instead (10-12).

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Desmoids are locally aggressive fibrous tumors with a tendency to recur. Desmoids can be intraabdominal, in the abdominal wall, or extraabdominal. Complications, such as compression or invasion of adjacent structures, and abscess formation can occur. Treatment options include observation, local treatment (surgery, radiotherapy), or systemic therapy (conventional chemotherapy, molecular targeted agents).

Lymph nodes, bones, lung, liver, and peritoneum are the most common sites of metastasis from bladder cancer. Tumors in a more advanced T category and those with atypical histologic features metastasize earlier. Tumors with atypical histologic features also have a higher frequency of peritoneal metastasis.

Desmoid-type fibromatosis (DF) is a locally aggressive fibroblastic neoplasm that has variable clinical and biologic behaviors ranging from indolent tumors that can undergo spontaneous regression to aggressive tumors with a tendency toward local invasion and recurrence. The management of DF has evolved considerably in the last decade from aggressive first-line surgery and radiation therapy to systemic treatment (chemotherapy, hormonal therapy, and targeted therapy) and symptomatic local control (surgery and radiation therapy). Imaging plays an important role in each of these treatment settings. In surgical candidates, computed tomography (CT) and magnetic resonance (MR) imaging are the modalities of choice for assessing resectability and surgical planning. For evaluating recurrence, MR imaging is the modality of choice for extra-abdominal recurrence, whereas CT is the preferred modality for intra-abdominal recurrence. Signal intensity changes at MR imaging can be used to monitor the biologic behavior of certain DFs chosen for expectant management. Response to systemic treatment with anti-inflammatory agents, hormonal therapy (eg, tamoxifen), cytotoxic chemotherapy (eg, doxorubicin, vinblastine, methotrexate), and targeted therapy (eg, sorafenib), as well as to radiation therapy, can be assessed at CT by monitoring size and attenuation changes or at MR imaging by monitoring size, T2 signal intensity, and degree of enhancement. Several patterns of response can be seen at imaging. Imaging also helps in detecting complications associated with systemic therapy and radiation therapy. (©)RSNA, 2016.

Limited data exist on safety and efficacy of immune checkpoint inhibitors (ICIs) among organ transplant recipients. The objective of this study was to report a case series of two patients with renal transplant who received treatment with an ICI and to conduct a pooled analysis of published cases to describe the safety and efficacy of ICIs in organ transplant patients. A systematic search in the Google Scholar and PubMed databases was carried out to include all the published cases of organ transplant patients who received treatment with ICIs including programmed cell death protein 1 (PD‐1), programmed death‐ligand 1, or cytotoxic lymphocyte antigen‐4 inhibitors since their inscription to January 31, 2019. In the present series of two cases with renal allografts who received pembrolizumab, one patient with squamous cell carcinoma of the skin experienced complete response (CR), whereas another patient with melanoma had a mixed response. Both patients experienced allograft rejection, but graft was salvaged. The pooled analysis of 64 patients published in literature showed that overall allograft rejection rate is 41% in organ transplant recipients following ICI therapy. The graft rejection rate was 44% (17/39) for renal, 39% (7/19) for liver, and 20% (1/5) for cardiac allografts. The highest risk was seen among patients who were treated with PD‐1 inhibitors, 20/42 (48%)—13/24 (54%) on nivolumab and 7/18 (39%) on pembrolizumab. The risk was lowest with ipilimumab, 23% (3/13). The overall response rate (CR + partial response [PR]) was 20% with ipilimumab, 26% with nivolumab, and 53% with pembrolizumab, whereas disease control rate (CR + PR + stable disease) was 35% with ipilimumab, 37% with nivolumab, and 53% with pembrolizumab. None of the variables including age, gender, type of cancer, type of allograft, type of immunosuppression, time since transplantation to initiation of ICI, and prior history of rejection were significantly associated with the transplant rejection on univariate analysis. The efficacy of ICI among patients with organ transplant appears promising, warranting testing in prospective clinical trials. The risk of rejection and allograft loss is considerable; therefore, the risk and alternative form of therapies should be thoroughly discussed with the transplant patients prior to initiating ICI therapy. Implications for Practice Transplant recipients are at higher risk of developing cancers. Although immune checkpoint inhibitors have been shown to improve the outcome in more than one cancer type, transplant recipients were excluded from these trials. Most of the data on the safety and efficacy of immune checkpoint inhibitors in transplant patients are based upon case series and case reports. The pooled data from these reports suggest that anti‐programmed death‐ligand 1 inhibitors have reasonable safety and efficacy among organ transplant patients, which warrants testing in clinical trials.

Malignant PEComas in our study were large tumors that most often arise in the kidneys and uterus and metastasize to lungs, liver, or peritoneum. In our experience malignant PEComas should be considered in the differential diagnosis of large well-circumscribed renal and uterine tumors.

Two different radiologic and clinical manifestations of ipilimumab-associated colitis were observed: the diffuse colitis pattern and the SCAD pattern.