A Rare Case of A Pseudosarcomatous Stromal Tumor: A Unique Benign Ampullary Tumor

ABSTRACT

We present a case of a pseudosarcomatous stromal proliferation of the ampullary and duodenal mucosa and its treatment in an asymptomatic 61-year-old man with a history of prostate adenocarcinoma and carotid paraganglioma. There is a modicum of literature describing these cases and treatment involving the gastrointestinal tract. The intricacy of diagnosis can further complicate management which necessitates the need for discussion between the clinician and the pathologist to avoid unnecessary invasive intervention. Our example of a pseudosarcoma involving the ampullary and duodenal mucosa and its treatment is unprecedented, therefore, should serve as an example for similar cases.

INTRODUCTION

Pseudosarcomatous stromal proliferation is a rare, benign lesion usually found in submucosal stroma of the urinary bladder, with few reports in the gastrointestinal tract. Treatments include surgical, endoscopic resection, laser ablation, photodynamic therapy, and/or chemotherapy. In this study, we present a case of pseudosarcomatous stromal proliferation involving the ampullary and duodenal mucosa.

CASE REPORT

A 61-year-old man with a history of prostate adenocarcinoma status postprostatectomy, carotid paraganglioma status postcomplete resection and metabolic-associated liver disease who was incidentally found to have a duodenal mass on MRI obtained to assess liver stiffness. The patient was asymptomatic and was referred for endoscopic visualization. A 20 mm × 17 mm, friable, fungating, and ulcerated nonobstructing ampullary mass was discovered, suggestive of ampullary adenocarcinoma. Biopsies were obtained and demonstrated reactive epithelial stromal changes. Multidisciplinary discussion was performed including surgical oncology, with recommendations for endoscopic ultrasound with fine needle biopsy, which again demonstrated stromal proliferation and reactive changes without submucosal invasion. Laboratory results including CA 19-9, CA-125, CEA, IgG4, and liver function tests were normal. The patient subsequently underwent endoscopic papillectomy, which was successful with R0 resection. Pathology demonstrated substantial fibroblastic/myofibroblastic stromal proliferation involving the ampullary and duodenal mucosa with marked reactive epithelial changes and gastric mucin cell metaplasia, consistent with pseudosarcomatous stromal changes (Figure 1). There was no evidence of any malignancy, including sarcomatoid prostate carcinoma or paraganglioma.

Figure 1.

(A) Ampullary duct lesion; (B) ampullary duct lesion with narrow band imaging; (C) EUS of ampullary duct lesion; (D) ampullary mucosa and rind-like proliferation of spindle cells; (E) high-power view; (F) 3-month follow-up postresection.

DISCUSSION

As is noted in our patient, an asymptomatic 61-year-old man with a history of prostate adenocarcinoma and carotid paraganglioma presenting after findings of a duodenal mass after evaluation for metabolic-associated liver disease concerning for malignancy. Of significance, his prior tumors were both treated surgically and confirmed without evidence of nodal involvement or metastatic carcinoma. After multiple biopsies, evaluations, endoscopic ultrasound, and multidisciplinary discussions, treatment with endoscopic papillectomy with R0 resection was performed. Pathology was referred out for expert consultation from the University of Miami and notable for fibroblastic/myofibroblastic stromal proliferation of the ampullary and duodenal mucosa, without evidence of malignancy, and in contrast to his other prior cancer diagnoses.

Pseudosarcomas are rapidly growing benign lesions that are difficult to differentiate from true dysplasia and malignancy which often leads to misdiagnosis as sarcoma and subsequent radical surgery.¹ While a few of these cases have been seen in the gastrointestinal tract, this finding is more commonly diagnosed in the urogenital tract.² The etiology of these tumors is unknown, although likely reactive proliferations caused by chronic inflammation, but may also occur at sites without history of surgery.¹

Furthermore, diagnosis of pseudosarcoma from a clinical perspective is difficult because there are no specific symptoms associated with these tumors, and evaluation with imaging and blood tests are not entirely reliable.³ Typical pathologic findings for these lesions include atypical stromal cells with mitotic proliferation which appear malignant, however, are negative with the use of immunohistology staining.⁴ In the case presented, the pathological findings were consistent with reactive epithelial changes and gastrin mucin cell metaplasia. Staining for ALK, CD34, CD117, DOG1, and S100 were negative and ruled out evidence of malignancy to include soft tissue tumors, gastrointestinal stromal tumors, melanoma, and neural tumors, leading to the diagnosis of a pseudosarcoma. Currently, the use of immunohistochemical stains and close communication between the clinician and pathologist for correlation with operative findings, history, and ancillary studies provide the primary means of diagnosis.⁵

Given the rarity of these cases within the gastrointestinal tract, treatment and follow-up of these lesions may be drawn from other notably similar cases. The mainstay of management is primarily focused on total excision of the lesion in concern.^6,7 On follow-up endoscopy at 3 months, complete removal of the lesion without recurrence was noted in our patient. In a similar tumor found in the esophagocardiac junction in 2022, complete excision by endoscopic dissection did not show recurrence of the lesion after 1-year follow-up.⁸

This is a rare case of pseudosarcomatous stromal proliferation involving the ampullary and duodenal mucosa. Given the patients benign presentation, surgical management was deferred in favor of endoscopic papillectomy. This pseudosarcomatous stromal proliferation and its treatment is unprecedented, therefore, should serve as an example for similar cases as correct diagnosis of these bizarre stromal proliferations will prevent potentially serious diagnostic pitfalls.^2,3,5

DISCLOSURES

Author contributions: JC Jones: Primary author; PI Quiles: Assisted with abstract and manuscript drafting. JG Quiles: Attending physician on case and assured high quality of case report. JG Edelson: Assisted with editing and drafting of case report. JC Jones is the article guarantor.

Financial disclosure: None to report.

Informed consent was obtained for this case report.

Previous presentation: This case was presented at the ACG Annual Scientific Meeting; October 28, 2024; Philadelphia, Pennsylvania.

ABBREVIATIONS:

ALK

anaplastic lymphoma kinase

CA 19-9

carbohydrate antigen 19-9

CA-125

cancer antigen-125

CD117

cluster of differentiation 117

CD34

cluster of differentiation 34

CEA

carcinoembryonic antigen

DOG1

Discovered on GIST-1

EUS

endoscopic ultrasound

FNB

fine needle biopsy

IgG4

immunoglobulin G4

MRI

magnetic resonance imaging

S100

100% soluble in ammonium sulfate