Ossifying Fibromyxoid Tumor of Soft Parts—A Clinicopathologic and Immunohistochemical Study of 104 Cases With Long-term Follow-up and a Critical Review of the Literature

Abstract

Ossifying fibromyxoid tumor (OFT) is a unique soft tissue tumor of uncertain histogenesis. The majority of reported cases (approximately 220) have pursued a benign clinical course. However, recent literature has emphasized the existence of morphologically atypical and clinically malignant examples of this tumor and proposed guidelines for assessment of biologic potential. In the present study, we evaluated 104 cases of OFT from the Armed Forces Institute of Pathology, accessioned between the years 1970 and 2007. Herein, OFT was strictly defined as a tumor with lobular architecture, predominantly epithelioid cell morphology, a low level of atypia, corded and trabecular growth patterns, moderate amounts of myxocollagenous matrix, and often, focal peripheral metaplastic bone formation. Tumors that lacked conventional morphology were excluded. The exclusion group included cutaneous mixed tumors, low-grade fibromyxoid sarcomas, and extraskeletal osteosarcomas. The OFTs occurred in 64 men and 40 women with a median age of 50 years (range, 21 to 81 y). The tumor size ranged from 0.7 to 17 cm (median, 3 cm). The mitotic rate varied from 0 to 41 mitotic figures per 50 HPFs (median, 2/50 HPFs). Tumor cell nuclei typically contained small, distinct nucleoli, and necrosis was infrequent (11/104). The great majority of tumors (67/71, 94%) were positive for S100 protein, whereas only occasional examples had (focal) positivity for desmin, glial fibrillary acidic protein, and an AE1/AE3 keratin cocktail. Local recurrences were documented in 9 of 41(22%) living patients, usually 10 or more years after primary surgery, but there were no metastases. A mitotic rate of >2 mitotic figures/50 HPFs was a risk factor for local recurrence, but necrosis, tumor size, the presence of satellite nodules, and positive margins were not. When OFT is strictly defined by the criteria noted above, there is potential for local recurrence, but there seems to be little or no risk for metastasis.

EWSR1 gene rearrangement occurs in a subset of cutaneous myoepithelial tumors: a study of 18 cases

“…These tumors show a distinctive lobulation and in most cases a bone shell is evident. [27][28][29] Metaplastic bone formation known in soft tissue myoepithelial tumors is not described in skin lesions. [1][2][3][4][5][6][7][8] Moreover, the intratumoral cytological and architectural heterogeneity of myoepithelial tumors is not a feature of ossifying fibromyxoid tumors in which uniform round to oval cells in cords and nests set in a myxohyaline stroma.…”

“…4,6,7 Immunohistochemical stains in this setting are of limited value because of the overlap with positivity for S100, GFAP, myogenic markers and rarely also keratins. 4,6,7,[27][28][29] Even though in a small number of cases investigated, ossifying fibromyxoid tumors show no abnormality in EWSR1. 10 In summary, our study demonstrated that cutaneous myoepithelial tumors harbor EWSR1 rearrangement in a subset of cases, and therefore are genetically related to soft tissue and bone myoepithelial tumors and the visceral counterpart in the lung.…”

Fibromyxoma of mandibular gingiva: a case study

“…These different X-ray appearances of the fibromyxomas pose a diagnostic problem with ameloblastomas, giant cell tumors, and intraosseous hemangiomas, as described in the literature; hence, a histopathological examination that provides confirmation of diagnosis is required [13,15]. The presence of calcifications found in the histopathological examination was also observed by Miettinen et al [12]. These calcifications are specific characteristics of the fibromyxomas and are essential for the differential diagnosis [11,16].…”

“…Studies on fibromyxoma of the maxilla are numerous, but those reporting the details of relationships with the surrounding soft tissues are rare [11,12]. This localization to the gingiva could be explained by the ectomesenchyme from the embryonic remnants of the periodontal ligament.…”

Epithelioid schwannoma or ossifying fibromyxoid tumour?

“…While epithelioid schwannoma can be described as a benign nerve sheath tumour of peripheral nerves, OFMT is considered to be a intermediate (borderline) malignant soft tissue tumour. There are differing opinions regarding the origin of the tumour (Kindblom et al, 1998;Miettinen et al, 2008).…”