SMARCA4-deficient sarcoma was first reported in the chest and recently in the uterus, but not in the stomach. Here, we present a patient diagnosed with SMARCA4-deficient sarcoma of the stomach, using histochemistry. An emergency operation was performed due to perforation of the tumor. However, one month after the operation, two nodes recurred, and six cycles of combination chemotherapy consisting of adriamycin and ifosfamide were administered. The combination chemotherapy showed a remarkable effect, and complete remission was achieved. The patient was alive without recurrence after 48-month follow-up. SMARCA4-deficient sarcoma is an exceedingly rare tumor with an extremely poor therapeutic response to anticancer drugs. Herein, we present the first case of SMARCA4-deficient sarcoma of the stomach, where a complete response to chemotherapy was achieved.

BCOR-CCNB3 fusion sarcoma is a recently described undifferentiated sarcoma with a novel recurrent inversion of 2 nearby genes BCOR and CCNB3. It typically affects bone and soft tissues of the pelvis, extremity, and paraspinal region and pursues variable clinical course. Primary renal BCOR-CCNB3 fusion sarcoma is very rare, and only a small number of cases have been documented. Accurate diagnosis is often challenging, and there is not any agreement for the treatment of this entity due to its rarity. We report findings of primary renal BCOR-CCNB3 fusion sarcoma in a 16-year-old boy with a brief review of the literature.

BCOR-rearranged sarcoma is the third common subtype of undifferentiated small round cell sarcoma and was first recognized in 2012 from bone sarcoma with a similar morphological manifestation with undifferentiated round cell but totally different molecular hallmark from Ewing sarcoma. Primary BCOR-rearranged sarcomas were mostly found in bone and soft tissue and were sporadically reported in viscera involving kidney, which add difficulties in differential diagnosis. Here we present a 21 years old male patient with BCOR-CCNB3 in neck, which first diagnosed as thyroid cancer.

We experienced a case of primary malignancy in giant cell tumor of bone (GCTB), arising in the right femur and harboring H3F3A mutation. A 27-year-old Japanese male without any prior disease history complained of pain in his right hip joint and right lower limb. Radiological images revealed an osteolytic and multicystic lesion existing mainly at the proximal epiphysis of the right femur. Preoperative clinical diagnosis was GCTB, although irregular marginal sclerosis was an atypical radiographic finding for conventional GCTBs. Biopsy sample from the lesion revealed the coexistence of typical GCTB and undifferentiated high-grade round cell sarcoma. Despite of the wide local resection of the tumor with preoperative and postoperative chemotherapy, the patient died of multiple distant metastases of the tumor 9 months after the surgery. Since heterozygous H3F3A c. 103G>T (p. Gly34Trp) mutation was detected not only in the biopsy sample from the primary site with typical GCTB and high-grade sarcoma components but also in the resected material from the metastatic site with only pure high-grade sarcoma component, the tumor was considered originally derived from conventional GCTB and acquire malignant transformation to high-grade sarcoma. Thus, this is an extremely rare case of primary malignancy in GCTB and the first case report of primary malignancy in GCTB proved the presence of H3F3A mutation even in the sarcoma component.