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Myofibrosarcomas are indolent low-grade or occasionally aggressive intermediate-grade sarcomas. They are a controversial entity. The pathologist is faced with the task of differentiating these rare tumors from benign reactive or pseudosarcomatous conditions.


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AGE Aged 33 to 73 years (median, 54 yrs; mean, 53 yrs)
SEX Equal



Myofibrosarcoma of the upper jawbones: a clinicopathologic and ultrastructural study of two cases.

Bisceglia M, Tricarico N, Minenna P, Magro G, Pasquinelli G.

Servizio di Anatomia Patologica, IRCCS-Ospedale Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy..
Ultrastruct Pathol. 2001 Sep-Oct;25(5):385-97. Abstract quote  

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 of the head and neck in children.

Smith DM, Mahmoud HH, Jenkins JJ 3rd, Rao B, Hopkins KP, Parham DM.

Department of Pathology, University of Tennessee, Memphis, USA.
Pediatr Pathol Lab Med. 1995 May-Jun;15(3):403-18. Abstract quote  

We have identified a distinctive malignant soft tissue neoplasm that occurred in the head and neck region of six children.

Histologically, these neoplasms presented an array of features ranging from low-grade spindle cell to high-grade fibrohistiocytic histologies and often had myoid characteristics. Ultrastructural and immunohistochemical studies indicated that they contained neoplastic myofibroblasts that were variably positive for vimentin (4 positive/4 tested), alpha-smooth muscle actin (4/5), muscle-specific actin (5/5), desmin (2/5), and v-src protein substrate p80/85 (4/5). Three patients died of rapidly progressive unresectable local disease, one died of metastatic and local disease, and two are alive 13 months and 8 years after wide resection.

We conclude that these neoplasms form a distinctive subset of pediatric soft tissue sarcomas that display an aggressive clinical behavior, typically with local recurrence, and exhibit features of myofibroblastic differentiation.



Myofibrosarcoma: a clinicopathologic study.

Montgomery E, Goldblum JR, Fisher C.

Department of Pathology, Georgetown University, Washington, DC, USA.
Am J Surg Pathol. 2001 Feb;25(2):219-28. Abstract quote  

The concept of soft tissue sarcomas composed predominantly of myofibroblasts has been controversial.

We examined a series of such lesions of low- and intermediate-grade malignancy to further define their clinical and pathologic features.

Histologic appearances of four cases diagnosed as myofibrosarcoma by electron microscopy were reviewed. Eleven additional cases with similar morphology were then identified from 249 tumors originally indexed as fibrosarcoma. Electron microscopy was performed on five of these, and immunohistochemistry was carried out on all cases for which material was available. There were 11 men and 4 women aged 33 to 73 years (median, 54 yrs; mean, 53 yrs). Lesions mainly involved the head and neck, extremities, and trunk and ranged in size from 1.5 to 12 cm. The tumors were composed of bland or pleomorphic stellate to spindled cells with eosinophilic cytoplasm and tapered nuclei in a collagenous stroma; 10 were grade 1 and five were grade 2. All sarcomas displayed fascicular or storiform patterns, and some of the grade 1 lesions superficially mimicked nodular fasciitis.

Electron microscopy of nine cases showed myofibroblastic differentiation, and immunohistochemistry showed smooth muscle actin in 13 of 15 cases, muscle-specific actin in 7 of 9, desmin in 6 of 14, and cytokeratin in 0 of 11. Four of nine grade 1 and three of four grade 2 tumors recurred (one twice), and one grade 2 tumor metastasized to the lungs.

Myofibrosarcomas are indolent low-grade or occasionally aggressive intermediate-grade sarcomas which can be recognized by light microscopy. Their clinical importance lies in the resemblance, particularly of low-grade examples, to reactive or pseudosarcomatous conditions.


Myofibrosarcoma of the bone: a clinicopathologic study.

Watanabe K, Ogura G, Tajino T, Hoshi N, Suzuki T.

Pathology Division, Fukushima Medical University School of Medicine Hospital, Fukishima City, Japan
Am J Surg Pathol. 2001 Dec;25(12):1501-7. Abstract quote  

Myofibroblastic tumors are fairly recently established soft tissue neoplasms. Although most of them appear to be benign, myofibrosarcoma of the soft tissue, seemingly their malignant counterpart, have been reported.

We describe the clinicopathologic and radiologic features of four cases of myofibrosarcoma arising from the bone. All but one of the patients were women ranging in age from 60 to 71 years. Two tumors occurred in the metaphyses of distal femurs and the others arose in the iliac bones. On radiologic examination all tumors exhibited well-demarcated lytic destructive lesions without periosteal reaction. Two tumors were localized in the bone, whereas the other two extended into surrounding soft tissues. Histologically, all tumors were composed principally of a mixture of a cell-rich fascicular area and a hypocellular fibrous area. In the former area tumor cells had rather eosinophilic spindle-shaped wavy cytoplasm and were arranged in interlacing fascicles and small storiform patterns with variable numbers of inflammatory cells. Tumors occasionally showed prominent pleomorphism, and large cells with hyperchromatic nuclei were seen. In contrast, hypocellular areas had various features, including collagenous, hyalinous scar-like and rarely keloid-like areas. Focal coagulation necroses were present in all but one tumor.

Immunohistochemically, the tumors were positive for vimentin, muscle actin (HHF35), alpha-smooth muscle actin, calponin, and desmin, whereas all of them were negative for high molecular weight caldesmon. On follow-up there was one fatal case with distant metastases, whereas the clinical courses of other cases after wide resection were excellent. Myofibrosarcoma of the bone has distinctive histopathologic features,



Myofibrosarcoma (low-grade myofibroblastic sarcoma) with intracytoplasmic hyaline (fibroma-like) inclusion bodies.

Gonzalez-Campora R, Escudero AG, Rios Martin JJ, Armas Padron JR, Vazquez AH, Vazquez Ramirez FJ.

Departamento de Anatomia Patologica, Hospital Universitario V. Macarena, Facultad de Medicina, Universidad de Sevilla, Avda Dr. Fedriani s/n, 41009 Seville, Spain.

Ultrastruct Pathol. 2003 Jan-Feb;27(1):7-11. Abstract quote  

Myofibrosarcoma is a controversial neoplasm composed of cells with differentiation toward myofibroblasts. The authors report an unusual case of myofibrosarcoma in which, in addition to the characteristic features reported, tumor cells contained intracytoplasmic hyaline (fibroma-like) inclusion bodies. A 66-year-old man complained of a painless enlarged mass in his right shoulder over the previous 6 months. The tumor recurred 2 years after operation.

On histologic examination, the tumor displayed diffusely infiltrative growth with isolation of individual skeletal muscle fibers. The tumor cells were most often arranged in an intersecting (herringbone) fascicular pattern but a vaguely storiform pattern was also observed. Cellularity varied from one area to another. The cells were spindle-shaped, with ill-define pale eosinophilic cytoplasm, and a wavy or tapering nucleus with fine chromatin and small nucleoli. Intracytoplasmic hyaline inclusion bodies of variable size, often located adjacent to the nucleus, were visible in numerous spindle and stellate cells. The mitotic index was 3/10 HPF. The tumor was scored as grade 1.

Immunohistochemistry revealed positive staining to muscle-specific actin, desmin and vimentin in most tumor cells. Intracytoplasmic hyaline inclusion bodies did not react specifically to any one antibody, but showed a marked ring-like immune reaction, particularly to muscle-specific actin. Electron microscopy showed tumor cells with indented nuclei and small nucleoli, abundant rough endoplasmic reticulum, micropinocytotic vesicles, and longitudinally arranged fine filaments with focal electron-dense patches and subplasmalemmal plaques.

The most striking feature was the presence of large, globular or ball-like, non-membrane-bound, randomly scattered clusters of fine filament, usually adjacent to the nucleus.



Leiomyosarcoma versus myofibrosarcoma: observations and terminology.

Eyden BP, Christensen L.

Department of Histopathology, Christie Hospital National Health Service Trust, Manchester, United Kingdom.
Ultrastruct Pathol. 1993 May-Aug;17(3-4):231-9. Abstract quote  

Two spindle cell sarcomas, which showed similarities in light microscopic histology and immunostaining and were diagnosed as leiomyosarcomas by these criteria, were compared ultrastructurally to show the value of electron microscopy in subtyping these neoplasms.

Both were subcutaneous, case 1 occurring in the nasolabial fold and case 2 in the upper calf. Both consisted of fascicles of spindle cells, and both stained positively for vimentin and alpha-smooth muscle actin; only case 2 stained additionally for desmin. Case 1 showed strong and case 2 weak or negative staining for fibronectin. By electron microscopy, case 1 contained prominent rough endoplasmic reticulum, peripheral fine filaments with focal densities, and fibronexus junctions.

By contrast, case 2 was characterized by an external lamina and well-developed bundles of fine filaments with focal densities. Case 2 was considered a typical leiomyosarcoma, and case 1 was interpreted as showing myofibroblastic differentiation. The nomenclature for these myofibroblastic tumors is discussed, and myofibrosarcoma and leiomyosarcoma



RECURRENCE Local recurrence possible


SURGERY Complete removal

Henry JB. Clinical Diagnosis and Management by Laboratory Methods. Twentieth Edition. WB Saunders. 2001.
Rosai J. Ackerman's Surgical Pathology. Ninth Edition. Mosby 2004.
Sternberg S. Diagnostic Surgical Pathology. Fourth Edition. Lipincott Williams and Wilkins 2004.
Robbins Pathologic Basis of Disease. Seventh Edition. WB Saunders 2005.
DeMay RM. The Art and Science of Cytopathology. Volume 1 and 2. ASCP Press. 1996.
Weedon D. Weedon's Skin Pathology Second Edition. Churchill Livingstone. 2002
Fitzpatrick's Dermatology in General Medicine. 6th Edition. McGraw-Hill. 2003.
Weiss SW and Goldblum JR. Enzinger and Weiss's Soft Tissue Tumors. Fourth Edition. Mosby 2001.

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Last Updated 1/5/2004

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