Multiple nodular fasciitis in the mandibular border area which is misdiagnosed as metastatic lymph node

Abstract

Nodular fasciitis (NF) is a benign lesion that has proliferative fibroblasts and myofibroblasts. NF is similar to a tumour and has infiltrative properties. We describe a rare case of multiple nodular fasciitis occurring in the mandibular border area of a 51-year-old male. Radiological and histological features are discussed along with a brief review of the literature. In addition, the importance of a differential diagnosis for this lesion is also discussed.

A 51-year-old male visited our hospital with an enlarging mass on the inferior border of the mandible. He had a nodular lesion that was rapidly growing and painful to palpation for 2 weeks prior to his visit. He had no trauma or surgical history and well controlled hypertension. Clinically, the lesion measured 1.5 × 2 cm and was sessile, firm and immobile. The lesion had normal skin colour and texture. No skin rash or ulceration was observed (Figure 1). Intraoral examination was within the normal range.

Figure 1.

Pre-operative clinical photograph. The lesion is sessile and has normal skin colour and texture

The pre-operative panoramic view showed no specific findings (Figure 2). MRI showed three round isointense masses which were 0.5 cm, 1 cm and 1.5 cm in size on the T₁ weighted image (WI) (Figure 3a). They were located under the mylohyoid muscle in a superioinferior manner and beneath the platysma muscle in a sagittal manner. They appeared as a slightly hyperintense signal on the T₂ WI (Figure 3b) and as a homogeneous, moderate enhancement on the T₁ WI (Figure 3a). There was no definite bone destruction in the surrounding area and no abnormal findings for the surrounding soft tissue. The presentation of the lesion suggested metastatic lymph nodes. We performed incisional biopsy using an extraoral approach under local anaesthesia.

Figure 2.

No specific findings are shown in the pre-operative panoramic radiography

Figure 3.

Pre-operative MR image. (a) Contrast enhanced T₁ weighted MR image. Three round isointense masses, which are 0.5 cm, 1 cm and 1.5 cm in size, are shown (arrows). They have a homogeneous, moderately enhanced signal. (b) Three round masses have a slightly hyperintense signal in the T₂ weighted MR image (arrows)

In the pathological diagnosis, highly proliferative fibrous tissue was observed with infiltrative growth into the periphery (Figure 4a). The spindle cells were strongly positive for proliferating cell nuclear antigen (PCNA), β-catenin and partly positive for α-smooth muscle actin (α-SMA) (Figure 4b,c,d). They were negative for S-100 and desmin (data not shown). Finally, the mass turned out to be nodular fasciitis (NF) with pseudosarcomatous proliferation. After these histological features were diagnosed as NF, the lesion was totally excised under general anaesthesia. The definitive diagnosis was confirmed as NF. No sign of NF recurrence was detected after the operation.

Figure 4.

Histological findings. (a) Proliferation spindle cells showed the whirling pattern in the vascular stromal tissue (haematoxyllin and eosin stain). (b) Many spindle cells in the peripheral pseudosarcomatous area are positive for proliferating cell nuclear antigen. (c) The proliferation spindle cells are strongly positive for β-catenin. (d) Diffuse positive reaction in the perivascular connective tissue for α-smooth muscle actin

Discussion

NF is a benign lesion that has proliferative fibroblasts and myofibroblasts. NF is similar to a tumour and has infiltrative properties.^1,2 It presents as a rapid growing fibroblastic tissue which is solitary and mostly painless although sometimes it presents with pain characteristics. People are commonly afflicted in the third to fifth decades of their life and there is no significant difference between genders.² The most prevalent region of NF is the upper extremities followed by the trunk.^2,3 The head and neck region is the next most prevalent region, with infants and children being affected.³ The pathogenesis of NF is unknown.² Local resection is the first choice of treatment. After total resection, recurrence is extremely rare.^1,2

Although NF usually has high signal intensities on T₁ WI and T₂ WI, various intensities of the signal have been observed. It may reflect the different kind of cellularity constituting NF such as collagen, cytoplasm, water content of the extracellular space and vascular content in the individual lesion.⁴ MR images of presented cases should be differentially diagnosed from multiple cervical lymphadenitis. Multiple cervical lymphadenitis on MR images is usually found in tubercular lymphadenitis,⁵ multiple myeloma⁶ and Hashimoto's thyroiditis.⁷ According to the disease progression and degree of nodal necrosis, cervical lymphadenitis also has a wide spectrum of signal intensity in the MR image.⁸ Therefore, careful clinical examination including a purified protein derivates test and a blood test is helpful for differential diagnosis.

Histologically, NF shows proliferative, tumour-like, immature fibroblastic lesions with rich cellularity and mitotic activity. Recognizable vascularity is often observed. Therefore, it is occasionally misdiagnosed as a sarcoma.^1,4 In immunohistochemical staining, NF contains vimentin and variable actin but does not have desmin, keratin or S-100 protein.² If the lesion is close to the salivary gland, benign and malignant diseases involved with the salivary gland should be included in the differential diagnosis. Pleomorphic adenoma and myoepithelioma are usually confused with NF. Positive immunochemical staining with cytokeratin and S-100 helps in the diagnosis of pleomorphic adenoma and myoepithelioma.⁴

In summary, we describe a rare case in which an adult patient presented with multiple NF in the inferior border of the mandible. NF has been frequently confused with malignancy.¹ In our case, the lesion was similar to a metastatic lymph node. Therefore, careful evaluation including histopathological and immunohistochemical examination was required for a differential diagnosis.