BackgroundLiquid biopsies enable the detection of circulating tumor DNA (ctDNA). However, the clinical significance of KRAS-mutated ctDNA for pancreatic cancer has been inconsistent with respect to its prognostic and predictive potential.Methods and findingsA total of 422 blood samples were collected from 78 patients undergoing treatments for localized and metastatic pancreatic ductal adenocarcinoma. KRAS mutation in tissues and KRAS ctDNA levels in plasma were determined by RASKET and droplet digital polymerase chain reaction. Longitudinal monitoring of KRAS ctDNA was performed to assess its significance for predicting recurrence and prognosis and for evaluating therapeutic responses to chemotherapy compared with carbohydrate antigen 19–9 (CA19-9). In 67 tumor tissues, discrepancies in point mutations of KRAS were rarely observed among individual patients, implying that one targeted point mutation of KRAS can be determined in tumor tissues prior to longitudinal blood monitoring. One-time blood assessment of KRAS-mutated ctDNA before surgery or chemotherapy was not clearly associated with recurrence and prognosis. Sequential blood monitoring was performed in 39 patients who underwent surgery for potentially resectable tumors. Increased CA19-9 levels were significantly associated with recurrence, but not prognosis (P<0.001, P = 1.0, respectively), whereas emergence of KRAS ctDNA was significantly associated with prognosis (P<0.001) regardless of recurrence. Furthermore, in 39 patients who did not undergo surgery, detection of KRAS ctDNA was a predictive factor for prognosis (P = 0.005). Multivariate analysis revealed that detection of KRAS ctDNA was the only independent prognostic factor regardless of tumor resection (hazard ratios = 54.5 for patients who underwent surgery and 10.1 for patients who did not undergo surgery; P<0.001 for both). Patients without emergence of KRAS ctDNA within 1 year after surgery showed significantly better prognosis irrespective of recurrence (P<0.001). No detection or disappearance of KRAS ctDNA within 6 months of treatment was significantly correlated with therapeutic responses to first-line chemotherapy (P<0.001). Changes in KRAS status provided critical information for the prediction of therapeutic responses.ConclusionsOur study showed for the first time that detection of KRAS ctDNA levels within a short period enables the prediction of prognosis and therapeutic responses in patients with pancreatic cancer.

Mesenteric leiomyosarcoma is a rare disease with poor prognosis. Previously, mesenteric leiomyosarcoma was not differentiated from gastrointestinal stromal tumor (GIST), which is the most common mesenchymal tumor of the gastrointestinal tract, and several cases of GIST may have been misclassified as mesenteric leiomyosarcoma. Thus, the actual clinicopathological characteristics of mesenteric leiomyosarcomas remain unclear. We herein describe a case of leiomyosarcoma arising in the descending mesocolon in a patient who developed metachronous liver metastasis. A 76-year-old woman reported a mass in her left upper abdomen. Computed tomography imaging revealed a low-density tumor adjacent to the descending colon. The patient underwent surgery and the tumor was resected along with part of the descending colon. Immunohistochemical differential diagnosis revealed that the tumor was positive for smooth muscle actin and desmin, and negative for CD117 (c-KIT) and S-100, which are characteristic of gastrointestinal leiomyosarcoma. A single liver metastasis developed 24 months after the operation. The patient underwent curative resection of the metastatic lesion. Sixteen months following surgery for the liver metastasis and 40 months after the initial removal of the primary lesion, the patient remains disease-free. The prognosis of leiomyosarcoma remains poor and standardized chemotherapy for this rare disease has not yet been established. Early diagnosis and surgical removal of the tumor is the only potentially curative option for liver metastasis of mesenteric leiomyosarcoma.

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IntroductionPseudomembranous colitis is known to be caused by Clostridium difficile; and, in 3% to 8% of patients, it lapses into an aggressive clinical course that is described as fulminant. We present here a case of extremely rapid and fatal fulminant pseudomembranous colitis that developed after ileostomy closure, a minor surgical procedure. To the best of our knowledge, this is the first case report of fatal fulminant pseudomembranous colitis after closure of a diversion ileostomy in an adult.Case presentationA 69-year-old Japanese man, who had previously undergone low anterior resection and creation of a diverting ileostomy for stage III rectal carcinoma was admitted for ileostomy closure. Preoperatively, he received oral kanamycin and metronidazole along with parenteral cefmetazole. His surgery and postoperative course were uneventful until the third postoperative day, when fever and watery diarrhea became apparent. The next day he presented with epigastric and left lower abdominal pain. Computed tomography revealed a slightly distended colon. Later that night, his blood pressure fell and intravenous infusion was started. In the early morning of the fifth postoperative day, his blood pressure could be maintained only with a vasopressor. Follow-up computed tomography demonstrated severe colonic dilation. A colonoscopy confirmed the presence of pseudomembranous colitis, and so oral vancomycin was administered immediately. However, within three hours of the administration, his condition rapidly deteriorated into shock. Although an emergent total colectomy with creation of an end ileostomy was performed, our patient died 26 hours after the surgery. The histopathological examination was consistent with pseudomembranous colitis.ConclusionIt is important to recognize that, although rare, there is a type of extremely aggressive pseudomembranous colitis in which the usual waiting period for medical treatment might be lethal. We consider that colonoscopy and computed tomography are helpful to decide the necessity of emergent surgical treatment without delay.

We herein describe the case of an adult with a complicated huge lymphangioma of the small bowel mesentery. Computed tomography (CT) confirmed a 45 × 30 × 14 cm multiple and separate, mixed and solid cystic tumor without enhancement by contrast medium in the abdominal cavity. Mesenteric CT angiography with three-dimensional (3D) reconstruction showed that the tumor did not involve the first jejunal artery, although the tumor did involve the subsequent jejunal and ileal arteries and the corresponding segment of the small bowel. Under anatomic guidance based on mesenteric CT angiography with 3D reconstruction, we were able to successfully excise the tumor. Mesenteric lymphangioma should be excised even when the tumor is asymptomatic. Mesenteric CT angiography with 3D reconstruction is useful for the surgical treatment of huge mesenteric tumors.