MPNST of the abdominal wall in a patient with lynch syndrome: A case report of a rare presentation and unique association

Abstract

Introduction: The abdominal wall is an extremely rare location for malignant peripheral nerve sheath tumors (MPNSTs). Besides presenting a rare location of MPNST, the peculiarity of our case lies in its association with Lynch syndrome, which is to our knowledge the first reported case of its kind.

Presentation of case: We present a case report of a 39-year-old male with a personal history of colonic cancer. Genetic counseling revealed Lynch syndrome with a heterozygous germline mutation in MLH1. Nine years after the right hemicolectomy, the patient presented with an asymptomatic lump in the abdominal wall. CT imaging showed a 3 cm mass in the aponeurosis of the right external oblique muscle. The patient underwent successful resection of the parietal tumor. Pathological examination revealed an MPNST. No additional treatment was warranted, and the patient exhibited no signs of relapse during the six months following the surgery.

Discussion: MPNSTs of the anterior abdominal wall are extremely rare and challenging. Some studies have investigated the presence of mismatch repair (MMR) deficiency in patients with sarcomas. Our case consolidates the hypothesis of an association between sarcomas and Lynch syndrome, which raises the question of the efficacy of immune checkpoint inhibitor therapy in these cases where treatment options remain limited.

Conclusion: It is essential to have a deep understanding of the growth patterns of MPNSTs in the context of syndromes that predispose individuals to tumors, like Lynch syndrome. This knowledge is crucial for accurately predicting patient outcomes and developing appropriate plans for monitoring and treatment.

Keywords: Case report; Lynch syndrome; MLH1; Malignant peripheral nerve sheath tumors; Sarcoma.

Fig. 1

Family pedigree. Proband indicated with a black arrowhead.

Fig. 2

CT imaging showing the tumor (a) Arterial phase axial view and (b) portal phase axial view CT images showing no specific pattern of enhancement of the tumor (White arrow) (c) Coronal view and (d) sagittal view CT images revealing a 3 cm mass (White arrow) in the aponeurosis of the right external oblique muscle with well-defined contours.

Fig. 3

Preoperative and postoperative views of the tumor (a) Preoperative picture showing a three-centimeter lump in the right upper quadrant distant from any surgical scar (b) Postoperative specimen showing a well-limited nodule measuring 4*3.5 cm.

Fig. 4

Histopathology images of the surgical specimen leading to the diagnosis of malignant peripheral nerve sheath tumor (a) Marbling Alternating tumoral hypercellular and hypocellular areas (x 100) (b) Fascicular connective tissue-like tumor proliferation (x 100) (c) Cytonuclear atypia with mitoses (x 400) (d) Wavy appearance of tumor cells (spindle cells) (x100).