Myofibrosarcoma of the Upper Jawbones: A Clinicopathologic and Ultrastructural Study of Two Cases

Abstract

Two problematic spindle cell sarcomas involving upper jawbones in two adult male patients have been studied by histology, immunohistochemistry, and transmission electron microscopy, and respectively graded as low-grade malignancy and high-grade malignancy. While any single methodological study did not allow confident classification of them into one or other of the classical categories of spindle cell sarcomas (fibrosarcoma versus leiomyosarcoma), the overall contribution from all three methodologies ultimately allowed them to be categorized as sarcomas with myofibroblastic differentiation. Histologically, both tumors had morphological features of an amalgama between neoplastic fibroblasts and smooth muscle cells. Immunohistochemically, both tumors expressed reactivity only for muscle specific actin and alpha smooth muscle actin, in addition to vimentin. Ultrastructurally, both tumors, while showing fibroblast-like cytoplasmic features, had a spurious and imperfectly organized cell surface defying convincing classification into any of specific categories (i.e., both appeared in terms of ultrastructure as poorly differentiated sarcoma, the former with low level of smooth muscle differentiation and possibly the presence of some fibronexus component, the latter with no smooth muscle differentiation but with possible evidence of very rare fibronectin fibril). Therefore, on balance, the most tenable diagnosis seemed to us that of a myofibrosarcoma in both cases. This work is presented considering the fact that myofibrosarcoma currently represents a topical theme of debate, and that this is the first report in medical literature concerning with myofibrosarcomas of the head and neck area in adults.

Myofibrosarcoma

“…These were compared with pleomorphic undifferentiated sarcomas, of which, in a similar period, 35% recurred, 59% metastasised and 41% of patients died of disease. Of the 15 other published examples defined using electron microscopy, 5 (33%) recurred and 10 (67%) metastasised [3,12,28,30,70,76]. Thus, myofibroblastic differentiation in pleomorphic sarcomas cannot be used as a favourable prognostic indicator.…”

“…Notwithstanding the extensive literature on MFH, there have been few well-documented clinicopathological reports of pleomorphic myofibrosarcoma [3,12,28,30,61,70,76]. A subset has been described in the head and neck region in children [70], but the tumours predominantly involve deep soft tissues of extremities in adults.…”

“…They occur at any age (range 9-75 years, mean 40 years) with a slight male predominance and with tumour size ranging from 1.5 cm to 17 cm. Tumours can arise in extremities and trunk (including breast or retroperitoneum), but there is a predilection (up to one-third of cases) for the head and neck region in both soft tissue (including oral cavity and especially tongue, face and neck) and bone (notably maxilla and mandible) [2,3,18,19,30,31,42,55,58,62,70,74,77].…”

Low-grade Sarcomas with CD34-Positive Fibroblasts and Low-Grade Myofibroblastic Sarcomas

“…Myofibroblasts were observed in well-differentiated fibrosarcoma in 1975 [109], and the first ''sarcoma of myofibroblasts'' was reported 3 years later [110]. About 50 cases have since appeared in the literature [104,[111][112][113][114][115][116][117][118][119][120][121][122].…”

Desmoplastic Fibroblastoma: A Light and Ultrastructural Description of Two Cases

“…The presence of fibronexus junctions on the surface of spindle or stellate cells identifies them as well-differentiated myofibroblasts, both in reactive and in neoplastic processes; the completely benign nature of this entity is furtherly confirmed by cytometric analysis. On the otherhand, the presence of fibronexus junctions is not always a set rule in less-differentiated, malignant myofibroblastic tumors [16]. These data emphasize the importance of ultrastructural examination of putative myofibroblastic lesions in constituting an evidence-based reference-point suited for refining light and immunohistochemical diagnosis of actinexpressing growths.…”