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Gastrointestinal stromal tumors are the most common mesenchymal tumors of the digestive tract, most of which are sporadic, and familial GISTs with germline mutations are rarely seen. Here, we report a 26-year-old female with a germline p. W557R mutation in exon 11 of the KIT gene. The proband and her father and sister presented with multifocal GIST and pigmented nevi. All 3 patients underwent surgery and imatinib therapy. To date, only 49 kindreds with germline KIT mutations and 6 kindreds with germline PDGFRA mutations have been reported. Summarizing the reported kindreds, the majority of familial GISTs manifest as multiple primary GISTs complicated with special clinical manifestations, including cutaneous hyperpigmentation, dysphagia, mastocytosis, inflammatory fibrous polyps, and large hands. Familial GISTs are generally thought to exhibit TKI sensitivity similar to that of sporadic GISTs with the same mutation.

UNASSIGNED: We report the first case of pathologic complete response (pCR) to neoadjuvant imatinib in a gastric stromal tumor harboring KIT mutations in both exons 11 and 9. The significance of this co-occurrence is unknown and might increase the responsiveness of gastrointestinal stromal tumors (GISTs) to imatinib.
UNASSIGNED: pCR of GIST to neoadjuvant imatinib is rare. We report a case of pCR to neoadjuvant imatinib in a gastric stromal tumor that harbored co-occurrence of multiple KIT mutations in exons 11 and 9. This co-occurrence in exons 9 and 11 is the first to be reported in the English literature.

Gastrointestinal stromal tumors (GIST) are mesenchymal spindle cell tumors of the gastrointestinal tract with the rarest occurrence in anal canal sites accounting for approximately only 2-8% of the anorectal GISTs. GISTs involve the expression of KIT (CD117) tyrosine kinase with the presence of mutations in KIT or platelet-derived growth factor alpha (PDGFRα) and are identified as an important target in therapy. The elderly population in the age of 70s appears to be at the highest risk with abdominal pain, GI bleeding, anemia, or weight loss as non-specific presenting symptoms. Here, we describe a case of a 56-year-old man who presented with vague dull pain in his left buttock diagnosed with GIST with a submucosal mass in the posterior wall of the anal canal and rectum and a tumor size of 45x42x37 mm. An immunohistological study of the biopsy sample reported positive for CD 117, CD 34, and DOG 1. The patient was prescribed neoadjuvant imatinib for 8 months with a good response and subsequently underwent transanal endoscopic microsurgical resection. Post-operatively, the patient was continued on adjuvant imatinib followed by regular restaging CT chest/abdomen/pelvis and surveillance flexible sigmoidoscopy every 6 months.

BACKGROUND: Neurofibromatosis type 1 (NF1) is characterized by café-au-lait patches on the skin and the presence of neurofibromas. Gastrointestinal stromal tumor (GIST) is the most common non-neurological tumor in NF1 patients. In NF1-associated GIST, KIT and PDGFRA mutations are frequently absent and imatinib is ineffective. Surgical resection is first-line treatment.
METHODS: A 56-year-old woman with NF1 was hospitalized because of an incidental pelvic mass. Physical examination was notable for multiple café-au-lait patches and numerous subcutaneous soft nodular masses of the skin of the head, face, trunk, and limbs. Her abdomen was soft and nontender. No masses were palpated. Digital rectal examination was unremarkable. Abdominal computed tomography was suspicious for GIST or solitary fibrous tumor. Laparoscopy was performed, which identified eight well-demarcated masses in the jejunum. All were resected and pathologically diagnosed as GISTs. The patient was discharged on day 7 after surgery without complications. No tumor recurrence was evident at the 6-mo follow-up.
CONCLUSIONS: Laparoscopy is effective for both diagnosis and treatment of NF1-associated GIST.

BACKGROUND: Systemic mastocytosis (SM), a rare myeloid neoplasm, is defined as a clonal and neoplastic proliferation of mast cells in at least one extracutaneous organ(s). The pathologic diagnosis and treatment of SM are challenging.
METHODS: We presented a 44-year-old male patient who had endured abdomen discomfort for 4 years and diarrhea for 5 months. Colonoscopy and PET/CT found a protuberant lesion in the cecum with adjacent lymphadenopathy. Histopathology of the cecum biopsy showed diffuse infiltration of medium-sized round/oval cells in lamina propria with immunohistochemical expressions of CD45, CD117, CD25, CD68, CD123, CD56, CD4, and CD35, mimicking blastic plasmacytoid dendritic cell neoplasm. Sanger sequencing revealed missense mutation (D816V) in the exon 17 of KIT gene. Serum tryptase level was 38.56 ng/ml. No abnormality was found in skin examination and bone marrow biopsy. No primitive cells were observed in bone marrow smear and peripheral blood smear. The diagnosis of aggressive SM with intestinal tract involvement was established. The patient received avapritinib treatment at an initial dosage of 200 mg once daily and exhibited dramatic clinical improvement but memory impairment within 1 month. No recurrence was observed in 1-year follow-up at the adjusted avapritinib dose (75 mg once daily).
CONCLUSIONS: SM is very rare and should be considered in patients with long-term diarrhea symptoms and hematopoietic/lymphoid-appearing tumors. KIT D816V mutation contributes to the differentiation of CD123, CD4, and CD56 immunoreactive SM from blastic plasmacytoid dendritic cell neoplasm. The rare side-effect of memory impairment in this case helps to accumulate the experience of avapritinib in treating KIT D816V-mutant SM.

Gastrointestinal stromal tumors (GISTs) have a significant risk of metastasis, although the degree varies in each case. The present report describes a case of late recurrence of GIST that was diagnosed 30 years after the primary tumor resection. An 80-year-old man was transported to Sanjo General Hospital (Sanjo, Japan) with hemorrhagic shock from gastrointestinal bleeding. Abdominal contrast-enhanced computed tomography revealed an 11.7-cm heterogenous tumor in the retroperitoneum adjacent to the third portion of the duodenum. The patient had a medical history of resection of \'leiomyoma\' of the upper jejunum when he was 50 years old. Pathological examination using archival pathological samples revealed that the previously excised tumor was GIST because the tumor cells showed positive immunoreactivity for KIT and DOG1. Treatment was started with imatinib, a selective KIT tyrosine inhibitor, even though endoscopy failed to provide biopsy specimens. Positron emission tomography conducted on the 28th treatment day revealed that imatinib completely shut down 18F-fluorodeoxyglucose uptake in the tumor, confirming that the tumor was imatinib-sensitive. A literature review yielded 12 GIST cases wherein metastases were diagnosed >10 years after primary tumor resection. Of the 12, four were originally diagnosed as benign. Clinicians should keep in mind that GISTs were formerly confused with non-GIST tumors and that there is a risk of relapse 10 years or later after curative surgery.

Gastrointestinal stromal tumors (GISTs) are uncommon GI tract cancers that develop from immature mesenchymal cells. It might be difficult to get an early diagnosis of people with small bowel GISTs, which can cause delays in therapy. We present here a case of a 62-year-old male with an incidental finding of a small intestine GIST during the workup for umbilical hernia. He presented with swelling above the umbilicus for the past six months that was progressive in nature and not associated with pain. Computer tomography (CT) of the abdomen with intravenous contrast revealed a heterogeneously enhancing mass lesion in the left paraumbilical intraperitoneal region, and immunohistochemistry results of the CT-guided biopsy showed a GIST. The patient underwent excision of the tumor with segmental resection and anastomosis, and supraumbilical hernia repair. Chemotherapy (imatinib for three years) after suture removal was planned for him.

UNASSIGNED: KIT is a proto-oncogene that is involved in the proliferation, survival, and regulation of melanocytes, mast cells, and the interstitial cells of Cajal. Mutations of KIT have been reported to be associated with hyperpigmentation and lentigines, mastocytosis, and gastrointestinal stromal tumors (GISTs). Some hotspot mutations of KIT have been reported to be associated with mastocytosis and GISTs, while the relationship between KIT mutations and hyperpigmentation and lentigines has not been fully elucidated.
UNASSIGNED: In this study, we presented a three-generation Chinese pedigree with progressive hyperpigmentation and generalized lentigines inherited in an autosomal dominant pattern. High-throughput sequencing was performed to capture genetic variations in peripheral blood samples of the proband. Also, Sanger sequencing was performed to further verify the result. We also reviewed previous literature on KIT mutations with hyperpigmentation and lentigines.
UNASSIGNED: A missense mutation of the KIT gene was identified: c. 2485G > C, which was co-segregated in the proband and his insulted father. Germline KIT mutations presenting as generalized hyperpigmentation and lentigines without systemic disorders are rare, with only two reports of c. 2485G > C mutation associated with this phenotype in previous literature.
UNASSIGNED: Our pedigree, together with those two reports, indicates a possible phenotype-genotype correlation of this germline KIT mutation, which might be helpful for genetic counseling, further functional segregation of KIT, and design of targeted therapy in the future.

UNASSIGNED: Mast cell leukemia (MCL) is a highly life-threatening and extremely rare subtype of systemic mastocytosis (SM). MCL often genetically contains one or more somatic mutations, particularly activating mutations of KIT. This study reported on an acute MCL patient who had a rare phenotype and genetic mutants with a history of primary malignant mediastinal germ cell tumor (GCT).
UNASSIGNED: A 30-year-old Asian male patient who underwent two rounds of surgery and chemotherapy with a history of primary mediastinal GCT (PM-GCTs) was admitted to our hospital due to persistent chest pain and severe fatigue. The diagnosis of acute MCL was confirmed via morphology analysis and chemical staining of marrow aspirate, as well as via marrow biopsy, with the addition of C-findings that included splenomegaly and cytopenia. The atypical MCs were phenotypically positive for CD117 and CD9 but weakly positive for CD2 and negative for CD25. Next-generation sequencing of the marrow aspirate identified heterozygous mutations in TP53 P301Qfs*44, FLT3 R973X, SETBP1 N272D, and JAK3 I688F, whereas mutations in KIT were not found. Although the initial therapy of corticosteroids, ruxolitinib, and dasatinib-based regimens was effective, he died of acute respiratory distress syndrome after the first cycle of chemotherapy with cladribine and cytarabine. The patient\'s survival time was 2.4 months after the initial presentation of MCL.
UNASSIGNED: In this case, MCL preceded by PM-GCTs had similar clinical symptoms and morphological manifestations but distinctly different genetic profiles than primary MCL. The characteristic morphology of MCL provides the most pivotal evidence that led our diagnosis in the correct direction. A competing hypothesis is that there is a common embryonal cancer stem cell between PM-GCTs and secondary MCL, and the latter is gradually developed in the context of additional \"driver mutations\".