Diffuse primary extra-gastrointestinal stromal tumor of the peritoneum: A rare case report.

RATIONALE: Gastrointestinal stromal tumors that present outside the gastrointestinal tract are known for extra-gastrointestinal stromal tumors (EGISTs) and they share the same morphological and immunohistochemical characteristics with gastrointestinal stromal tumors. Here we report a rare case of diffuse primary EGIST arising at peritoneum. PATIENT CONCERNS: A 57-year-old male presented to the hospital with abdominal pain and right lower abdominal tenderness. DIAGNOSIS: The core needle puncture biopsy showed epithelial-like cells and the nuclei were ovoid and focally elongated. Immunohistochemical examination was consistent with a primary EGIST of the peritoneum. INTERVENTIONS: The patient was treated with Imatinib mesylate. OUTCOMES: Five months later, there is no complication resulting from treatment. The follow-up abdominal contrast-enhanced CT showed the lesion was significantly decreased in size, and was evaluated as partial response. The patient continued the treatment with Imatinib as prescribed by the oncologist. LESSONS: EGISTs are rare and should be considered in the differential diagnosis of the peritoneal tumors and immunohistochemistry helps to confirm the diagnosis. Further study with longer follow-up is desired to characterize these uncommon tumors.

Primary alveolar rhabdomyosarcoma of retrorectal-presacral space in an adult patient: A case report of an uncommon tumor with rare presentation.

RATIONALE: Rhabdomyosarcoma (RMS) has known as a highly malignant soft tissue sarcoma, representing 5% to 10% of all solid tumors in childhood. Alveolar rhabdomyosarcoma (ARMS) of the retrorectal-presacral space is an extremely rare lesion for adult, no study has been reported in the English literature. PATIENT CONCERNS: A 51-year-old male presented with abdominal pain for 1 month, significantly worse when having a bowel movement. DIAGNOSIS: Computed tomography (CT) and magnetic resonance imaging (MRI) of the pelvis showed a solid-cystic, enhancing lesion of dimension located in retrorectal-presacral space. The surgical specimen was reported as ARMS after pathological evaluation. INTERVENTIONS: The tumor was complete surgical resection, and after surgery, the patient was treated with combination chemotherapy. OUTCOMES: At 23 months follow up, the patient was asymptomatic with no evidence of metastases or local recurrence. LESSONS: Improvements in imaging in addition to early surgical intervention and chemotherapy treatment are crucial to improve survival chances against RMS.