嚢胞変性により特異な形態を呈した胃GISTの1例

Gastric GIST Demonstrating a Specific Morphology Due to Cystic Degeneration, Report of a Case

要旨　患者は75歳，女性．胃精査のため紹介され受診した．胃X線検査では正常粘膜に覆われたふたこぶ状の柔らかい隆起性病変として描出され，内視鏡検査では隆起の頂部は発赤調だが基部が正常粘膜に比しやや褪色調を呈し，体位や送気により形態が変化した．超音波内視鏡検査にて腫瘍は第4層に存在し，内部に嚢胞形成を伴う単一の腫瘍であることが観察された．生検組織でGISTと診断され，噴門側胃切除術を施行した．切除標本の肉眼像では腫瘍は5×4×4cm，粘膜下層に主座を置き，内部に大きな嚢胞形成がみられた．組織学的には紡錘形細胞から成り，KITに陽性を示し，一部はαSMAにも陽性であった．核分裂像は50視野に5個未満であった．腫瘍内部の嚢胞変性により，特異なふたこぶ状の形態を呈したものと考えられた．

　The patient was a 75-year-old woman who was referred to our hospital for close examination of the stomach. X-ray examination of the stomach demonstrated a two-humped soft protruding lesion covered by normal mucosa. Endoscopy revealed that the top of the protruding lesion was erythrogenic and its base was slightly more brownish than the normal mucosa. It also showed morphological changes induced by air pumping and postural changes. Endoscopic ultrasonography revealed that the tumor mass located in the 4th layer of the mucosa was a single tumor accompanied by cystic formation inside. Based on the results of biopsy, the patient was diagnosed as having GIST, and proximal gastrectomy was performed. Macroscopic examination of the resected tissue sample revealed that the tumor, measuring 5×4×4cm, was mainly located in the submucosal layer of the stomach, and large cystic formation was observed inside the tumor. Histology demonstrated that the tumor mass consisted of KIT-positive spindle cells, some of which were also positive for αSMA. During microscopy, less than 5 karyomitotic images were observed in 50 fields of vision. These findings suggest that the specific two-humped morphology was due to cystic degeneration developing in the tumor.