Heavily Calcied Gastrointestinal Stromal Tumour of Stomach: A Diagnostic Dilemma

Gastrointestinal stromal tumours (GIST) are the most common mesenchymal tumour of gastrointestinal tract and the stomach being the most commonly involved organ. Focal calcication may be seen in GIST but prominent or heavy calcication is rare. Gastric mass with prominent calcication on imaging may create a diagnostic dilemma. We present a rare case of gastric GIST with heavy calcication in a 55 years old female presenting with abdominal lump. Computed tomography (CT) showed a large heterogenous juxta gastric mass with solid-cystic component with heavy calcication. She underwent laparotomy and en-bloc gastric sleeve resection with the mass. Microscopic examination showed tumour with spindle cell and calcication with mitotic index of 6/50 High power eld. Immunoreactivity with Vimentin, CD34 and DOG 1 conrmed diagnosis of GIST. Dystrophic calcication of necrotic or degenerative tissue is thought to be cause of calcication in GIST. Very few cases of heavily calcied GIST have been reported in literature, our case is of interest because presence of solid cystic component and a huge size ~ 14 cm (longest diameter).

oesophagus (< 1 %) in few cases. 1,2 They have an exophytic growth pattern and may also have cystic degeneration, necrosis, haemorrhage although calci cations were uncommon. Focal calci cation within GIST has been reported, ranging from 10-50% in reported series. 3,4,5 However, extensive thick calci cation is a rare phenomenon. 1

Case Presentation:
A 55-year-old woman presented to our outpatient department with an abdominal lump for 6 months duration associated with upper abdominal discomfort without any family history of malignancy. There was no history of any bleeding in form of hematemesis or malena or loss of appetite or weight. Her prereferral ultrasound showed a large solid cystic mass reported to be arising from pancreatic. General examination was unremarkable. Abdominal examination revealed a large ~ 14 x 10 cm hard multilobulated mass in the epigastrium with restricted mobility. Computed Tomography showed a large juxta gastric (near lesser curvature) mass with solid and cystic component with heavy calci cation ( Fig. 1) compressing duodenum, head of pancreas, left lobe of liver; there was no evidence loco-regional lymph node enlargement. Endoscopic ultrasound showed a large heterogenous solid cystic mass probably arising from peripancreatic region ( Fig. 2A). Cyst uid analysis showed normal CEA and CA 19 − 9 level. Considering the large size of the mass, laparoscopic resection was not attempted and open approach was preferred. Intra-operatively, a large 14 x 12 cm exophytic mass was arising from stomach wall (more towards lesser curvature) and it was resected en bloc with a sleeve of stomach. Cut specimen showed a variegated solid cystic mass with areas of sclerosis and dense calci cation (Fig. 2B).
Postoperative course was uneventful and she was started on oral diet on POD 2 and discharged on POD 5. Histopathology showed partially encapsulated spindle cells, arranged in short fascicles with nuclear palisading. Immunohistochemistry con rmed the diagnosis of gastric GIST (Fig. 3). It showed a positive reactivity with CD 34, DOG 1, vimentin and negative for CD 117, desmin, SMA and S100. Mitotic index was 6 per 50 High power eld and Ki67 index was 6%. Considering size of the tumour & mitotic index, she was started on adjuvant imatinib therapy. On follow up at 2 years she is healthy and disease free on radiological evaluation.

Discussion:
The stomach is the most common location of GIST but accounts 2-3 % of all gastric tumours. Usually presents as a mass arising from wall of stomach with extra-gastric extension. The extra-gastric location also makes it di cult to appreciate the origin of the tumour, especially with large tumours. Careful evaluation of gastric wall thickening may give clue to the diagnosis. A peripheral enhancement pattern was present in majority on CECT. Central areas of low attenuation correspond to haemorrhage, necrosis or cyst formation. Patchy calci cations may occur within the primary mass of large GISTs, and the reported series have indicated a wide variability among these (10-50%). 19 Heavy calci cation is a rare feature, seen only in 3% cases. 20 Extensive calci ed GIST has been reported only few cases in the literature. Indeed, only nine cases have been reported till now in our search, six cases arising from stomach 6-13 and three from colorectum.
Clinically, a large peri-gastric mass with prominent calci cation includes various differentials from pancreas, solid pseudopapillary tumour or mucinous neoplasms which may be associated with peripheral calci cations (egg shell calci cation). Serous cyst adenoma will have central calci cations (sunburst calci cation). This cystic neoplasm of pancreas may also present with calci cation. Diffuse calci cation may be associated with mucin producing adenocarcinoma stomach. Production of PDGF (platelet derived growth factor) and BMP (bone morphogenic protein) has been proposed as a stimulator of osteoblastic lineage, which also play important role in regulation of bone formation. 12 Pathologically, dystrophic calci cation is most accepted theory. 13 It usually occurs in degenerated tissues like necrosis or haemorrhage. In alkaline environment, the binding of denatured protein to both phosphate and calcium ions ultimately forms calcium phosphate precipitates. 16 Several reports of calci cation in metastatic sites of GIST after starting treatment with imatinib, perhaps follows a different mechanism of calci cation. 14,15 The biological behaviour of calci cation in GIST also has been evaluated by researchers. Kim et al, 17 showed no CT features other than size correlated with the biological behaviour. However, case reports have shown GIST with prominent calci cation carries a less aggressive behaviour with indolent course because of their low mitotic index. 18 Our case a rarity of clinical presentation with such a heavily calci ed GIST with solid cystic component and a largest size reported in literature. In conclusion, gastric GIST may also present with calci cation and should be consider as differential diagnosis in patients presenting as calci ed solid cystic mass in epigastrium. Behari critically revised the manuscript for important intellectual content. Vinay K Kapoor supervised the process and approved the nal draft. Bappaditya Har is the corresponding author and is the article guarantor. All the authors have read and approved the nal paper to be submitted for publication.

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