Primary and metastatic high-grade pleomorphic sarcoma/malignant fibrous histiocytoma of the gastrointestinal tract: an approach to the differential diagnosis in a series of five cases with emphasis on myofibroblastic differentiation

Abstract

Primary and metastatic so-called malignant fibrous histiocytoma/undifferentiated high-grade pleomorphic sarcoma (MFH) is rare in the gastrointestinal (GI) tract with approximately 50 primary and five metastatic cases reported so far. We evaluated two primary gastric and three metastatic intestinal high-grade pleomorphic sarcomas with features of storiform-pleomorphic MFH. Gastric tumours occurred in a 79-year-old man and a 68-year-old woman. One patient died post-operatively, and the other was disease-free at 6 months. Three patients presented with GI metastasis 24, 60 and 0 months after diagnosis of MFH of the heart (n = 1) and the thigh (n = 2). Metastases were located in the small (n = 1) and large bowel (n = 2) and were characteristically pedunculated and polypoid with oedematous haemorrhagic stroma. Concurrent metastases (brain, lung, bone) were present in all three cases. Tumours expressed alpha-smooth muscle actin (four of five), platelet-derived growth factor receptor (PDGFR) alpha (three of three) and PDGFRbeta (two of three) but were negative for CD117, CD34 and other lineage-specific markers. Ultrastructural examination revealed myo/fibroblastic features. Both gastric MFH were wild type for KIT and PDGFRalpha. In conclusion, primary and metastatic MFH of the GI tract commonly express PDGFRalpha and show a myo/fibroblastic phenotype. They should be distinguished from a variety of primary and metastatic pleomorphic neoplasms, in particular high-grade sarcomatous GI stromal tumours (GIST), pleomorphic leiomyosarcoma, sarcomatoid carcinoma and other mimics.

An approach to pleomorphic sarcomas: can we subclassify, and does it matter?

“…8,19,20 Many of these tumors show focal immunoreactivity for smooth muscle actin, but stains for desmin and h-caldesmon are typically negative. 21 Some examples also show rare cytokeratin-positive cells, which can cause confusion with those tumors in which a sarcomatoid carcinoma is a real consideration. [22][23][24] Thus, focal immunoreactivity for any number of intermediate filaments is, in my opinion, insufficient evidence of a specific line of differentiation and should not dissuade one from rendering a diagnosis of UPS.…”

Metastatic malignant fibrous histiocytoma to sigmoid colon presenting as a huge abdominopelvic mass on combined positron emission tomography/computed tomography

“…To the authors' knowledge, this is the first report of MFH metastatic to the SC detected by PET/CT. In a series of three cases with metastatic MFH of the GI tract, the involved sites were reported as small bowel, left colon and rectum (2). Unlike our case, multiple further organ metastases were diagnosed before or concurrent to GI metastases in all patients with conventional imaging methods (2).…”

“…In a series of three cases with metastatic MFH of the GI tract, the involved sites were reported as small bowel, left colon and rectum (2). Unlike our case, multiple further organ metastases were diagnosed before or concurrent to GI metastases in all patients with conventional imaging methods (2). In another case report consisting of nine patients, the small intestine was detected as the most frequently involved part of the GI tract from metastatic MFH (3).…”

Peritoneal Dissemination from Malignant Fibrous Histiocytoma of the Buttock: Unusual Metastases from a Rare Tumor

“…Actually, however, surgical resections of metastatic tumors may improve quality of life and manage complications related to metastasis although they did not prove the survival benefit. The patient in this case received inevitable yet aggressive local treatments for rare complications caused by the metastatic tumors in the small intestine, [5][6][7] and in the bone. He also received radiotherapy to chest to prevent a metastatic tumor from invading into aorta.…”