Nodular Fasciitis

Nodular (pseudosarcomatous) fasciitis is a presumably reactive vascular and fibroproliferative response to injury.  The lesion is benign but has a rapid rate of growth and a histopathologic appearance which can be quite alarming. Although relatively common, it was not recognized as a separate histopathologic entity until 1955.  Approximately 17% of all cases occur in the head and neck region, usually the neck and face.

In the mouth, nodular fasciitis is usually a discrete submucosal nodule which is slightly tender and is not freely movable beneath the mucosa.  It seldom achieves more than 2 cm. in size and is usually more superficially located than fibromatosis of the oral region. While occurring at all ages, this entity is most often diagnosed in persons 30-40 years of age, with no gender predilection.

Nodular fasciitis presents as haphazardly arranged bundles of fibroblasts in a myxoid or mucoid background. An important diagnostic feature is a fine capillary network arranged in a radial pattern around a larger central vessel or vessels. The fibroblasts are typically large and plump, similar to those of granulation tissue. Pleomorphic fibroblasts may be present, and mitoses are common but not plentiful or abnormal. A variable amount of collagen and acid mucopolysaccharide are seen in the intercellular matrix, although the latter may not be readily visible without special staining with alcian blue or colloidal iron. Scattered chronic inflammatory cells are typically present in small to moderate numbers, and long-standing lesions may demonstrate foamy histiocytes and osteoclast-like multinucleated giant cells with 2-6 nuclei. When striated muscle is involved (intramuscular fasciitis), it is completely replaced by the fibrovascular proliferation, unlike proliferative myositis, which infiltrates between muscle fibers.

The spindle-shaped fibroblasts in this lesion tend to be arranged in long fascicles which are slightly curved, whorled or S-shaped. They seem especially prone to extension along the fibrous septa of submucosal fatty tissues. Small slit-like spaces often separate the fibroblasts, and extravasation of erythrocytes is commonly seen, although it is seldom extensive. Occasional microcysts are seen in older lesions, perhaps coalesced into larger cystic spaces. The lesion is not often encapsulated but is usually well demarcated from surrounding tissues.

Ultrastructural studies have confirmed the presence of myofibroblasts in nodular fasciitis, with a basic fibroblast appearance but with peripherally located bundles of myofilaments with dense patches similar to those of smooth muscle cells. Lesional cells are immunoreactive to vimentin, smooth muscle actin, and muscle-specific actin, but not for desmin.

The differential diagnosis of this lesion includes fibrosarcoma, fibrous histiocytoma and liposarcoma, few of which demonstrate the vascular component of nodular fasciitis. The scattered inflammatory cells also help to differentiate the lesion. Occasional lesions will demonstrate very small foci of metaplastic bone or cartilage (ossifying fasciitis, fasciitis ossificans, parosteal fasciitis), tempting the pathologist to diagnose the case as osteosarcoma. Nodular fasciitis can also arise within blood vessels (intravascular fasciitis) and in deep fascia (fascial fasciitis).

Despite its often aggressive microscopic appearance, nodular fasciitis is a self-limiting lesion which is readily treated by simple local excision. Deeper lesions tend to be somewhat larger and less well demarcated, hence, require a wider local excision. Recurrence rates vary from 1-6% with this treatment and some lesions have been reported to regress and disappear without treatment.

The major prognostic factor here is an accurate diagnosis and recurrences should, therefore, be evaluated very carefully. Earlier studies have shown that as many as one-fourth of all cases were erroneously interpreted as malignant and, conversely, numerous cases of well-differentiated fibrosarcoma have been misdiagnosed as nodular fasciitis.

Price EP Jr, Siliphant WM, Shuman R. Nodular fasciitis: a clinicopathologic analysis of 65 cases. Am J Clin Pathol 1961; 35:122. 85. Soule EH. Proliferative (nodular) fasciitis. Arch Pathol 1962; 73:437.

Werning JT. Nodular fasciitis of the orofacial region. Oral Surg Oral Med Oral Pathol 1979; 48:441-446.

Diaz-Flores L, Martin Herrera AI, Garcia Montelongo R, Gutierrez Garcia R. Proliferative fasciitis: ultrastructure and histogenesis. J Cutan Pathol 1989; 16:85-92.

DiNardo LJ, Wetmore RF, Potsic WP. Nodular fasciitis of the head and neck in children. A deceptive lesion. Arch Otolaryngol Head Neck Surg 1991; 117:1001-1002.

Montgomery EA, Meis JM. Nodular fasciitis. Its morphologic spectrum and immunohistochemical profile. Am J Surg Pathol 1991; 15:942-945.

Lai FM-M, Lam WY. Nodular fasciitis of the dermis. J Cutan Pathol 1993; 20:66-69.

Price S, Kahn LB, Saxe N. Dermal and intravascular fasciitis: unusual variants of nodular fasciitis. Am J Dermatopathol 1993; 15:539-543.