Objectives: Mast cells (MCs) have been proposed to be involved in the pathophysiology of irritable bowel syndrome (IBS). Nonetheless, the quantity and distribution of MCs in the gastrointestinal tract of pediatric patients with IBS are not well defined. This study aimed to compare the number of MCs in children with and without IBS and to establish histopathological reference values in pediatrics. Methods: Forty-nine participants with IBS were prospectively enrolled and classified into IBS with atopy (n = 29) and IBS without atopy (n = 20). As our retrospective control group, we selected 42 individuals with a history of polyposis syndrome or gastroesophageal reflux disease with normal histopathology. Retrospective selection of the control cohort was performed in a manner similar to previously published adult and pediatric studies. MCs were prospectively stained immunohistochemically on specimens from the stomach, duodenum, terminal ileum, and descending colon of both groups. Results: The IBS group showed significantly more MCs per high-power field (MCs/HPF) in the stomach, duodenum, terminal ileum, and descending colon (P < 0.001), irrespective of their atopic status. Optimal MC cutoff values for IBS are ≥20.5 MCs/HPF in the stomach (area under the curve [AUC] = 0.84); ≥23.0 MCs/HPF in the duodenum (AUC = 0.79); ≥33.5 MCs/HPF in the terminal ileum (AUC = 0.82); and ≥22.5 MCs/HPF in the descending colon (AUC = 0.86). Conclusions: Pediatric patients with IBS showed increased numbers of MCs in the stomach, duodenum, terminal ileum, and descending colon when compared with controls. Further trials are needed to explain the role of MCs in pediatric IBS, which might facilitate the development of targeted therapeutic interventions.

Unusual clinical course Background: Thymic carcinoma is a rare malignant neoplasm. High-grade thymic carcinoma has a high recurrence rate following surgery, and a low 5-year survival rate. Approximately 30% of patients with thymic carcinoma will be asymptomatic at the time of diagnosis. Extrathoracic metastasis on presentation is uncommon. Treatment of the primary tumor includes surgery, chemotherapy, and fractionated radiation. A rare case of thymic carcinoma that presented with bone and cerebral metastases is reported in a patient who responded well to stereotactic radiosurgery and chemotherapy. Case Report: A 63-year-old woman presented to the hospital for evaluation of hip pain. She was diagnosed with a lytic bone lesion of the right femur and brain metastasis. Biopsies from the mediastinal mass and right femur showed histological features consistent with carcinoma. Immunohistochemistry showed positive immunostaining of the tumor cells for the c-kit receptor (CD117) and CD5, supporting a diagnosis of stage IVb thymic carcinoma. Treatment included stereotactic radiosurgery, which delivered multiple radiation beams to the tumor tissue from different directions to target the tumor without affecting normal tissues. She was treated as an outpatient with carboplatin and taxol after stereotactic radiosurgery. The patient recovered well following treatment. Conclusions: A case of thymic carcinoma with bone and cerebral metastases was successfully treated with stereotactic radiosurgery and chemotherapy.

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