Rare Fibroblastic and Myofibroblastic Tumors

Abstract

This review discusses the clinical presentation, histopathologic characteristics, and diagnostic and treatment algorithms for several distinct fibroblastic and myofibroblastic tumor subtypes. Low-grade fibromyxoid sarcomas typically arise in the deep soft tissues of the proximal extremities or trunk in young adults. They tend to have a high local recurrence rate, although some may have distant metastases. Histologically, they consist of bland fibroblasts with a whorled or linear arrangement alternating with hypocellular myxoid stroma. Sclerosing epithelioid fibrosarcomas typically arise in the deep soft tissues of the lower extremities of middle-aged adults. They tend to be slow growing but clinically aggressive, with a high propensity for local recurrence and distant metastases. Classic histologic features include the presence of small, uniform, ovoid epithelioid cells with sparse cytoplasm, arranged in cords within a sclerotic fibrous stroma. Myxoinflammatory fibroblastic sarcomas mainly affect the hands and feet. They are prone to local recurrence, with a very low likelihood of distant metastasis. Histologically, they have nodular architecture and highly cellular areas with an abundance of inflammatory cells, among which characteristic large Reed-Sternberg–like and lipoblast-like cells and hypocellular areas rich in myxoid stroma can be seen. Inflammatory myofibroblastic tumors typically occur in children and young adults, with common anatomic locations being the omentum, mesentery, retroperitoneum, and lung. Histologically, they are composed of myofibroblastic spindle cells accompanied by a lymphoplasmacytic inflammatory infiltrate. Surgical resection is the mainstay of treatment for all of the above tumor types. Radiation therapy may be used as adjuvant therapy for tumors with a high risk of local recurrence, in the setting of positive margins, or for unresectable primary or metastatic disease. There is no definite role for standard chemotherapy, but in certain cases, targeted therapy may be of use, such as ALK inhibitors in ALK-positive inflammatory myofibroblastic tumors. Key words: inflammatory myofibroblastic sarcoma, low-grade fibromyxoid sarcoma, myxoinflammatory fibroblastic sarcoma, sclerosing epithelioid fibrosarcoma