Nodular Fasciitis as a Pseudosarcomatous Lesion in the Ligamentum Nuchae: A Case Report

Nodular fasciitis is a non-neoplastic proliferative soft-tissue lesion that frequently arises in the deep subcutaneous region or in the fascia of the upper extremities, the head and neck, the lower extremities, and trunk 1, 2). It is infrequently misdiagnosed as a malignant tumor, especially as a sarcomatous lesion because it grows very rapidly without evidence of associated infection. Furthermore it shows histologic findings similar to those seen in malignant tumors, such as high cellularity, increased mitotic activity, and an infiltrative growth pattern. Despite its malignant microscopic appearance, nodular fasciitis is a self-limiting lesion that is cured following marginal excision.

The purpose of this report is to present nodular fasciitis as a pseudosarcomatous lesion occurring in the ligamentum nuchae.

A 20-year-old woman presented with a 1-month history of a progressively enlarging, tender mass on her posterior neck. She underwent fine-needle aspiration under ultrasonography at a local hospital. The pathologic diagnosis was spindle cell neoplasm. Then, she was transferred to our hospital. Neck computed tomography (CT) images showed a markedly enhancing, well-defined, ovoid soft tissue mass posterior to the spinous process of C2 (Fig. 1 A-C). She had no evidence of inflammation or any trauma history. She underwent marginal excision. Excised mass was 2 cm-size, non-capsulated and pinkish gray mass (Fig. 2A).

Fig. 1
(A) A CT scan of the soft tissuted tomography reveals a 1.2 cm sized oval shaped well-defed mass. (B) A CT scan of the soft tissuted tomography with enhancement reveals a strongly enhancing soft tissue mass between the superficial and deep muscle layers of the posteor neck. (C) A CT scan of the soft tissuted tomography with sagittal reconstruction shows that the mass is located posterior to the spinous procesof C2.

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Fig. 2
(A) A Llongitudinal section of nodular fasciitis (x1.25 magnifations). (B) Histopathologic findings under the hematoxylin-eosin stain. The lesion is composed of interlacing fascicles of plump spindle-shaped fibroblasts/myofibroblasts lacking nuclear pleomorphism. The prominentculatures, and intralesional extravasated erythrocytes, and mixed chronic inflammat cells werear seen (H&E ×200). (C) Mitoses were present in 6/10 high power fields but no atypicforms were are idenified (H&E, ×400).

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Histologically, the lesion was composed of interlacing fascicles of plump spindle-shaped fibroblasts/myofibroblasts lacking nuclear pleomorphism. It included prominent vasculatures and intralesional extravasated erythrocytes, and mixed chronic inflammatory cells (Fig. 2B). The myxoid area, hyalinization, giant cells and bone formation were not seen. Mitoses were present in 6/10 high power fields, but no atypical forms were identified (Fig. 2C). Immunohistochemical study showed diffuse positive cytoplasmic staining for smooth muscle actin (SMA) that was negative for desmin, S-100, CD34 and C-kit. We finally diagnosed as nodular fasciitis because the lesion occured along the fascia of the neck muscle and was typically small, approximately 2-3 cm in size.

She recovered without any complications and there has been no evidence of reccurenece for 6 months.

Nodular fasciitis is a benign soft tissue lesion composed of fibroblast proliferation.1) The lesion is usually a non-encapsulated oval shaped mass and is yellowish-brown to grayish-white in color. It is the most common benign lesion that is misdiagnosed as sarcoma on fine-needle aspiration cytology (FNAC).3) Overall, 21-30% of nodular fasciitis cases are misdiagnosed as sarcoma, and 36% of cases are misdiagnosed as other benign lesions.4, 5, 6) The reason for this is that it grows rapidly without signs of infection or trauma, and histologically it has abundant spindle-shaped cells, increased mitotic activity, and infiltrative borders. Nodular fasciitis is known to be the pseudosarcomatous lesion.

The pathogenesis of nodular fasciitis is still unknown, However, reactive or inflammatory processes have been proposed.7, 8) Past trauma history has been suggested as a provoking factor, although most cases of nodular fasciitis have been reported to be associated without trauma.1, 9, 10)

Nodular fasciitis is common in young adults between 20 and 40 years of age and occurs equally often in men and women. However, any age group can be affected.1, 7) It can be found anywhere in the body. Half of these cases involve the upper extremity and approximately 15-20% involve the head and neck.10)

The most common clinical presentation of nodular fasciitis is often a solitary, rapidly growing mass that is frequently associated with pain and tenderness within a few weeks. However, slower or no growth with a diameter of 1-3 cm has been reported that in the majority of cases.1)

Ultrasonography shows that nodular fasciitis consists of welldefined and solid, hypoechoic, or mixed echoic masses with indistinct posterior margins and distal acoustic shadowing.7) On CT and MRI, nodular fasciitis is a well defined, homogeneous soft tissue mass with moderate to strong enhancement.7) In most cases, it presents as subcutaneous nodule. Deeper located lesions, which belong to the intramuscular type, are larger and have poorly defined margins. These can invade the adjacent structures including the bone and are likely to suggest a soft tissue malignancy.1, 11)

Regardless of its aggressive microscopic feature, nodular fasciitis is a self-limiting lesion that is readily treated by marginal excision. Recurrence of nodular fasciitis is rare, if the initial diagnosis is accurate. Recurrent lesions frequently reveal a malignant tumor. Spontaneous regression of nodular fasciitis has occasionally been observed.12) Wong et al. reported spontaneous resolution of nodular fasciitis that occurred in 41 of the 46 cases within 1 to 16 weeks (median, 2 weeks) after FNAC.13)

In our case, the result of FNAC at local hospital showed spindle cell neoplasm. We had to suspect both benign and malignant tumor. Because mass was located superficially, small size and well defineded, we expected that it could be resectable. We planned to do primary excisional biopsy for diagnostic and treatment purpose rather than to do repeated FNAC or incisional biopsy.

The different pathologic features of nodular fasciitis compared with those of malignant sarcomas are small size (usually less than 5 cm), no pleomorphism, plentiful mitotic figures without atypical forms, and even chromatin (Table 1).14)

Table 1
Pathologic Differences Between Nodular Fasciitis and Malignant Sarcomas

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Although there are no pathognomonic imaging findings, nodular fasciitis should be included in the differential diagnosis of soft tissue masses in the head and neck, especially in patients with a recently developed, rapidly growing mass and a history of recent trauma.

We report a case of nodular fasciitis on the posterior neck. Though nodular fiscitis usually shows aggressive characteristics in microscopic appearance, it is a self-limiting lesion that is readily treated by marginal excision. Nodular fasciitis should be included in the differential diagnosis of soft tissue masses in the head and neck, especially in patients with a recently developed, growing mass. Further follow-up is required for this case to determine recurrence.