Possible two diagnosis
Case 331
【Progress】
The patient returned to the orthopedic local clinic with the MRI CD images with radiological findings and possible imaging diagnosis.
【Discussion】
Malignant fibrous histiocytoma (MFH) is known as one of the most common malignant soft tissue tumors, followed by leiomyosarcoma, malignant neurinoma, liposarcoma and fibrosarcoma.
Malignant fibrous histiocytoma (MFH) was categorized into three or four types: pleomorphic, myxo-fibrotic, giant cell, inflammatory. Pleomorphic type is the most and myxo-fibrotic is the second-most (1). Now, Pleomorphic type MFH is currently termed undifferentiated pleomorphic sarcoma, and myxo-fibrotic MFH, called myxoid fibrosarcoma (2, 3).
What is MFH driven from? MFH composes of various tissues such as fibrous tissue, histiocytes-like cells, necrosis, hemorrhage and even calcification. It is considered that MFH is driven from fibrocytes/fibro myoblasts or stem cells differentiating to form soft tissue (2, 3).
On MRI, reflecting various tissue components of MFH, signal intensity of MFH is not homogeneous but inhomogeneous various signal intensity from high, iso and low signal intensity on T1WI and T2WI, indicative of vial tumor, necrosis, hemorrhage and calcification. MRI images on MFH is expressed as ‘fruit bowel sign’ of various signal intensity reflecting various components of MFH (4).
Although no review articles exist on ADC values of MFH, Boruah DK, et al reported that ADC values of malignant tumors are around 1.0 including those of MFH values are around 0.9. Further, they stated that cutoff vales of malignant tumors differentiating from benign tumors are around 1.2 (4).
In our case, the lesion includes parenchyma and cystic component with calc or hemosiderin in radial flexing muscle whose ADC values are 1.117 to 1.452. At first, it was considered that its images of MRI look like Myxoid MFH, in short, currently myxoid fibrosarcoma but not meet ADC values of malignancy. ADC values of this tumor is corresponded to benign tumor. Then, the final image diagnosis is neurinoma of benign tumor rather than myxoid fibrosarcoma.
Actually, neurinoma is categorized into two types: Antoni A type, filled with compact neurinoma parenchyma, Antoni B type, cystic degeneration inside surrounded by compact neurinoma parenchyma in the surroundings (5, 6).
Our case might be a typical Antoni B type neurinoma based on that the tumor includes cystic component surrounding solid tumor parenchyma whose ADC values of the tumor parenchyma are over 1.2 (4).
【Summary】
We presented an eighty-two-year-old female for a mass of right elbow joint. MRI with fat suppression T2WI depict a lesion with cystic component surrounding tumor parenchyma of high signal intensity whose ADC values are over 1.4 indicative of benign tumor. It is borne in mind that Antoni B type neurinoma compose of cystic component inside surrounding tumor parenchyma. As malignant solid tumor, malignant fibrous histiocytoma that is once known as one of the most malignant soft tissue tumors, is currently termed undifferentiated pleomorphic sarcoma and myxoid fibrosarcoma. ADC values less than 1.2 might be a help to differentiated malignant soft tissue tumor from benign soft tissue tumor.
【References】
1.Di Muzio B., Gaillard F. 2016. Malignant Fibrous Histiocytoma / Radiology Reference Article / Radiopaedia.oRg.http://radiopaedia.org/articles/malignant-fibrous-histiocytoma
2.World Health Organization Classification of Tumors: Pathology and Genetics of Tumors of Soft Tissue and Bone. Edited by Fletcher CDM, U. K., Mertens F., Lyon, France, IARC Press, 2002.
3.Seomangai K, et al. Malignant fibrous histiocytoma, now referred to as Undifferentiated Pleomorphic Sarcoma: A Case Report of an unexpected histology of a subcutaneous lesion. Int J Surg Case Rep. 2019; 60: 299–302.
4.Boruah DK, et al. Added Value of Diffusion-Weighted Magnetic Resonance Imaging in Differentiating Musculoskeletal Tumors Using Sensitivity and Specificity: A Retrospective Study and Review of Literature. Cureus. 2021 Jan; 13(1): e12422.
5.Skolnik AD, et al. Cranial Nerve Schwannomas: Diagnostic Imaging Approach. Radiographics. 2016;36 (5): 150199. doi:10.1148/rg.2016150199 - Pubmed citation
6.Louis DN, et al. The 2007 WHO classification of tumours of the central nervous system. Acta Neuropathol. 2007;114 (2): 97-109.
2024.4.12