►Calcifying fibrous tumor of the stomach – a case report

Introduction

A calcifying fibrous tumor (CFT) is a rare benign mesenchymal tumor affecting children and young adults ^[4] and shows a predilection for deep soft tissues of the extremities and the abdominal cavity ^[2,4]. CFT of the tubular gastrointestinal tract is very rare ^[5].

CFTs are histologically characterized by fibroblastic spindle cell proliferation ^[6] within a hypocellular densely hyalinized stroma ^[6,7], psammomatous or dystrophic calcifications, and lymphoplasmacytic infiltrates ^[2].

Case Presentation

A 24-year-old male patient with morbid obesity, weighing 143 kg and a BMI of 48, came to the Bariatric surgery department for sleeve gastrectomy. He had no obstructive sleep apnea or GERD. Complete blood counts were within normal limits. Thyroid function tests were also normal. Liver enzymes were near normal. Lipid profile showed reduced HDL (36mg/dl) and increased non-HDL (137 mg/dl). The patient underwent laparoscopic sleeve gastrectomy.

The specimen consisted of a closed tubular segment of the stomach measuring 17x3 cm. External surface smooth gray tan, on cut section submucosal nodule, was seen measuring 1.0x0.6 cm. The cut section of the nodule was gray-white, which lies 2.5 cm from the stapled margin. Microscopy showed sections from the gray-white submucosal nodule, a tumor composed of sparse spindle cells embedded in dense hyalinized collagenous stroma with areas of chronic inflammation and psammomatous calcification. The tumor cells were wispy with tapering ends in parallel to the collagen bundles. The inflammatory cells were composed of a mixed population of lymphocytes, plasma cells, and a few eosinophils. At places, few lymphoid follicles were noted. The tumor was located in the submucosa, with intact, unremarkable surface epithelium. No evidence of gastritis, H. pylori-like organisms, or malignancy was seen.

Fig.1 Histologic findings of submucosal tumor. (A) Gastric mucosa. (B) Tumors are composed of sparse spindle cells embedded in a dense hyalinized collagenous stroma. (C) Areas of chronic inflammation and psammomatous calcification.

Properly controlled immunohistochemical stains showed the thin spindle cells embedded in the hyalinized stroma to be positive for Vimentin and CD34 (patchy, weak) while negative for CD117, DOG1, S100, EMA, PR, Desmin, SMA, and MSA. A diagnosis of Calcifying fibrous tumor was offered. Calcifying Fibrous Tumor is a benign lesion, so pathological staging was not done. Lymph nodes were not commented on, as they are benign lesions and do not metastasize. Cancer biomarkers were not needed for this case as the lesion was benign and incidentally detected. Differential diagnosis considered was Gastrointestinal stromal tumor (GIST), which was ruled out by negative CD117 & DOG 1 IHC. Leiomyoma was ruled out by negative Desmin IHC.

Fig.2 Immunohistochemical analysis of submucosal tumor. (A) Vimentin positive. (B) CD34 positive. (C) CD117 negative.

Discussion

A calcifying fibrous tumor (CFT) was first described by Rosenthal et al. in 1988 as a childhood soft tissue tumor with psammoma bodies ^[3]. It was previously named a calcifying fibrous pseudotumor ^[1] and was thought to represent a reactive process resulting from abnormal tissue healing ^[5].

Reported cases of gastric CFTs have been documented with a mean age of 53 years, no sexual predominance, and involving the body of the stomach and the posterior wall ^[5]. There are 48 cases of gastric CFT reported in the literature ^[3], including gastric CFT presenting as an ulcer ^[5].

CFTs have been documented in various anatomical sites, including the mesentery, peritoneum, mediastinum, pleura, lung, adrenal glands, paratesticular, and spermatic cord. Although CFTs have been reported in various organ systems, the gastrointestinal tract is rarely involved ^[7,8].

The pathogenesis of CFTs remains unclear, but it has been hypothesized that CFT may represent a late sclerosing stage of inflammatory myofibroblastic tumor (IMT) ^[2]. Evidence has suggested that these lesions may be associated with IgG4-related diseases ^[6].

Gastric CFTs are most often detected incidentally and present without symptoms or with nonspecific symptoms such as abdominal pain, dyspepsia, flatulence, nausea, vomiting, altered bowel habits, loss of appetite, weight loss, and fatigue. Gastric CFTs may occasionally be associated with more severe manifestations, including gastric ulcers and bleeding per rectum ^[6].

Imaging findings of CFT show coarse calcification on conventional ultrasound and peripheral hypoenhancement without central enhancement on ultrasound with contrast. A CT scan shows a mildly enhanced, well-circumscribed homogenous mass with calcification ^[6]. On MRI, the lesion appears as an isointense signal mass on gadolinium-enhanced T1-weighted imaging and hypointense on T2-weighted imaging ^[9].

The differential diagnosis of gastrointestinal CFT includes gastrointestinal stromal tumor (GIST), schwannoma, leiomyoma, solitary fibrous tumor, inflammatory myofibroblastic tumor (IMT), plexiform fibromyxoma, fibromatosis, and reactive nodular fibrous pseudotumor (RNFP) ^[6]. CFTs are difficult to distinguish from GIST ^[1] as they are frequently hyalinized with dystrophic calcifications. Lymphoplasmacytic infiltrate and psammomatous calcifications are not features of GIST ^[4].

Table 1: differential diagnosis of gastrointestinal CFT ^[6].