27 Characterization of Low-Grade Fibromyxoid Sarcoma in Abdominopelvic and Retroperitoneal Locations: A Clinicopathologic Analysis of 11 Cases

Document Type

Conference Proceeding

Publication Date

3-24-2025

Publication Title

Lab Invest

Keywords

mucin 4, abdominal cavity, abdominal wall, adult, aged, child, clinical article, conference abstract, diagnosis, duodenum, electronic medical record, female, fibrosarcoma, follow up, gene rearrangement, human, immunofluorescence, immunohistochemistry, mesentery, metastasis, omentum, retroperitoneum, sarcoma, spindle cell, transverse colon, tumor recurrence, tumor volume

Abstract

Disclosures: Beena Ahsan: None; Nasir Ud Din: None; Fatima Safdar: None; Kerem Ozcan: None; Abbas Agaimy: None Background: Low-grade fibromyxoid sarcoma (LGFMS) is an uncommon, slow-growing tumor that usually develops in the lower extremities. Its occurrence in the abdominal cavity, pelvis, and retroperitoneum is extremely rare. This study seeks to explore the clinicopathologic features and immunohistochemical and molecular profile of LGFMS in these unusual locations. Design: We analyzed 11 cases of LGFMS found in the abdominopelvic region and retroperitoneum. Clinical data were collected from electronic medical records. Immunohistochemical stains were carried out using antibodies against MUC4, smooth muscle actin (SMA), EMA, S100, CD34 and CD117. Additionally, FUS rearrangement was assessed in a subset of cases. Results: Age ranged from 5 – 75 years (median 40 years), with a female predominance (F:M 10:1). Out of 11 LGFMS cases from several sites: intra-abdominal/abdominal wall (3 cases), retroperitoneum (2 cases), pelvis (2 cases), small intestine mesentery (1 case), duodenum (1 case) transverse colon (1 case) and omentum (1 case). Tumor sizes ranged from 5 to 35 cm (median 10.5). Histologically, the tumors were characterized by spindle cells with mild to moderate atypia, arcade vessels with perivascular sclerosis and myxoid nodules alternating with hyalinized areas. The omental case shows hybrid morphologic features of LGFMS and sclerosing epithelioid fibrosarcoma. All cases tested positive for MUC4, and FUS gene rearrangement was identified in one of two cases examined. All cases were negative for EMA, SMA, S100, CD34 and CD117. Follow-up data were available in 8 patients. 1 patient died of disease. Remaining 7 patients are alive and free of disease (follow-up period 1 – 60 months, median 12 months). Conclusions: LGFMS occurring in these central areas shows clinicopathologic characteristics similar to those found in the extremities. Our study shows a striking female predominance compared to previous studies. Our results also differ from earlier studies in terms of tumor recurrence, as none of our patients experienced a recurrence. However, LGFMS is notorious to recur or metastasize after long periods (over 10 years) and some of our patients may still develop late recurrence/metastasis.

Volume

105

Issue

3

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