Skeletal Radiology

, Volume 33, Issue 5, pp 300–302

Rapid involution of proliferative fasciitis


    • Department of RadiologyIwate Medical University School of Medicine
  • Shigeru Ehara
    • Department of RadiologyIwate Medical University School of Medicine
  • Jun Nishida
    • Department of Orthopedic SurgeryIwate Medical University School of Medicine
  • Takashi Satoh
    • Department of Pathology IIIwate Medical University School of Medicine
Case Report

DOI: 10.1007/s00256-003-0738-6

Cite this article as:
Kato, K., Ehara, S., Nishida, J. et al. Skeletal Radiol (2004) 33: 300. doi:10.1007/s00256-003-0738-6


A process of evolution and involution is a characteristic feature of reactive fibrous lesions, but has not been emphasized in either the radiology or pathology literature. We report a case of proliferative fasciitis, pseudotumorous fibrous proliferation similar to nodular fasciitis, showing evolution and involution during a 1-month period. A 35-year-old Japanese woman presented with a tender soft tissue mass in the forearm that had grown over a 2-week period. MR imaging revealed a soft tissue mass of nonspecific signal intensity on the muscle fascia. Needle biopsy revealed diffuse proliferation of fibroblastic spindle cells representing proliferative fasciitis. Two weeks after biopsy the mass had rapidly decreased in size, and the pain subsided. MR imaging obtained 1 month later demonstrated only minimal residual reactive change along the fascia. Conservative treatment may be a reasonable treatment option for this condition.


ForearmProliferative fasciitisSpontaneous regressionSoft tissue tumorMagnetic resonance imaging


Evolution and subsequent involution is typical of an inflammatory process, rather than neoplasm, with some exceptions. Spontaneous regression has been reported in malignant neoplasms, such as malignant lymphoma, melanoma and choriocarcinoma [1]. Proliferative fasciitis is a pseudosarcomatous reactive proliferative lesion of soft tissue, similar to nodular fasciitis. It may grow rapidly, but rapid regression is rarely observed [2]. In this paper, we describe the rapid regression of proliferative fasciitis along with a brief discussion.

Case report

A 35-year-old Japanese woman presented with a firm soft tissue mass on the dorsal aspect of the forearm. The mass had grown over a 2-week period. On physical examination, a 4×3 cm mass was attached to the deep muscular layer on the dorsal aspect of the right forearm. Past medical and family histories were noncontributory. MR imaging revealed a soft tissue mass attached to the muscle fascia that was isointense to muscle on T1-weighted images and of higher signal intensity than other tissues on spin-echo T2-weighted images. The mass had a fuzzy border with no capsule or pseudocapsule, and the overlying subcutaneous fat was slightly edematous (Fig. 1). Needle biopsy was performed, and revealed immature fibroblast-like spindle cells and ganglion-cell-like giant cells in the background of a mucoid matrix representing proliferative fasciitis (Fig. 2). Two weeks after biopsy, the mass rapidly decreased in size, and the pain subsided (Fig. 3). The patient preferred observation to surgical treatment. MR images obtained 1 month later, 6 weeks after the initial MR examination, demonstrated only minimal residual reactive change along the fascia (Fig. 4). Follow-up telephone communication 3 years and 6 months later indicated that no recurrence had occurred.
Fig. 1A, B

Initial conventional spin-echo MR imaging. A Axial T1-weighted image (TR 560 ms, TE 25 ms), B axial spin-echo T2-weightged image (TR 1,800 ms, TE 100 ms). A soft tissue mass is seen attached to the extensor muscle fascia with a broad base. The border is fuzzy with reticulated increased signal intensity in the surrounding fat, representing edema or other inflammatory change. The signal intensity is nonspecific

Fig. 2

Photomicrograph (hematoxylin-eosin stain). Fibroblast-like spindle cells and scattered giant cells (arrows) are seen in the mucoid-rich background

Fig. 3

Fast spin-echo T2-weighted MR image (TR 3,000 ms, TE 104 ms) performed 2 weeks after the biopsy. The size of the mass has significantly decreased (arrows)

Fig. 4

Fast spin-echo T2-weighted MR image (TR 2,000 ms, TE 100 ms) 1 month after Fig. 3 (6 weeks after Fig. 1). There is only minimal residual change in the fascia (arrow). The mass was not palpable


Proliferative fasciitis occurs in adults between 40 and 70 years of age. About two-thirds of the lesions occur in the extremities, especially in the forearm and the thigh. They usually present as a firm palpable subcutaneous nodule that is movable and unattached to the overlying skin, and in most patients they grow rapidly for a few weeks [3]. The histological findings closely resemble those of another pseudosarcomatous lesion described as proliferative myositis [3]. Proliferative fasciitis, arising from the fascia, is a subcutaneous variant of proliferative myositis. The active proliferation of immature-appearing cells may lead to an incorrect diagnosis of sarcoma [4, 5]. The etiology of proliferative fasciitis is unknown. Although mechanical trauma has been implicated, a history of preceding injury is rare [3, 6].

Imaging findings of proliferative fasciitis have not been well discussed. Those of nodular fasciitis, a similar lesion, vary according to the subtype (myxoid, cellular, fibrous) and the location (subcutaneous, intermuscular, intramuscular) [7, 8].

Nodular fasciitis and proliferative fasciitis are known to be reactive fibrous proliferations with rapid growth, but descriptions of spontaneous involution are scarce. Particularly with imaging findings, the rapid evolution and involution as seen in this patient is only rarely observed. Surgical resection is an option for treatment, but is not indicated in lesions with rapid regression.

This type of involution and evolution is typical of an inflammatory process. Although it is not typical of neoplastic proliferation, it may be seen uncommonly in some neoplastic processes, such as malignant lymphoma [1]. Follow-up policy should be based on the histology of lesion.

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