Nodular fasciitis of the submandibular gland

Discussion

Nodular fasciitis is a benign proliferating fibroblastic tumour which is most commonly found in the upper arms but can be found in any part of the body including the salivary gland.1 Majority of nodular fasciitis lesions in the salivary gland have been reported to be intraparotid.2 Nodular fasciitis most commonly presents in adults of age 20–50 years.3 4 The tumours are usually less than 4 cm. Typically, they are self-limiting potentially self-regressing and non-recurring.3–5 Aetiology is often unknown. There has only been one published case on nodular fasciitis in the submandibular gland to date by Chen in which we find similarity in the case presentation of a non-painful lesion of 2 cm size and absence of red flag symptoms such as weight loss, night sweats and dysphagia.6 In Chen’s case, ultrasound, MRI and Fine Needle Aspiration Cytology (FNAC) were suggestive of pleomorphic adenoma but definitive diagnosis of nodular fasciitis was only made after the tumour was excised.6 In fact, nodular fasciitis in other areas has been reported to be misinterpreted to be pleomorphic adenoma as both tumours show features of spindle shaped cell or plasmacytoid cells. Pleomorphic adenoma has been the most common benign tumour of salivary gland.6 There is another published case report titled ‘Nodular Fasciitis in the submandibular gland’ but the reported tumour was actually in the parotid gland.7

Ultrasound-guided core biopsy is minimally invasive and has been widely used as diagnostic tool in making the presumptive diagnosis for salivary gland lesions due to its high sensitivity of 92%–94% and specificity of 99%–100%.8

It has been reported that the features of pleomorphic adenoma on ultrasound are usually well-defined, regular or lobulated, poor vasculature, hypoechoic with posterior acoustic enhancement.9 10 Nodular fasciitis on ultrasound could show varying features of lobulated or irregular or well-defined features, isoechoic or hypoechoic with or without posterior echo enhancement.11–13 In the present case, the ultrasound features of the lesion match the features of pleomorphic adenoma in the literature, which is the most common benign tumour in submandibular gland. However, these features are also present in nodular fasciitis. The ultrasound features of nodular fasciitis and pleomorphic adenoma are similar and not specific enough to differentiate between them.

Although pleomorphic adenoma is also a benign tumour, it has a risk of future malignancy change and recurrence. As the ultrasound result of our case suggested pleomorphic adenoma, the curative treatment would be complete excision. However, it was histologically diagnosed as nodular fasciitis as the excised tumour consisted of bland spindle cells with immunopositivity with actin, CD68 and S-100. It has been reported that nodular fasciitis specimens mainly consist of spindle cells and actin as compared with pleomorphic adenoma, immunohistocytologically nodular fasciitis consist of spindle cells that stain positive with actin and vimentin, while pleomorphic adenoma is positive for S-100.6 14 15 This suggests that although core biopsy has been highly accurate, only small pieces of specimen were obtained, it is difficult to derive a conclusive diagnosis without looking at the histology of the entire tumour specimen.

While pleomorphic adenoma has a malignant transformation rate of 1.5% in first 5 years and can recur, nodular fasciitis is usually non-recurring and self-resolving.3–5 16 Nodular fasciitis does not always require excision. However, as demonstrated in the literature and in our case, ultrasound and core biopsy can be inadequate in making the diagnosis of nodular fasciitis in submandibular gland.

If the core biopsy or FNAC showed a nodular fasciitis, a patient based discussion on management with watch and wait approach in view of a repeat core biopsy may be considered to avoid surgery while ensuring that the lesion does not progress and no red flag symptoms present. Surgery would have been avoided if the lesion self-resolve during the surveillance period. This would save patient from an invasive procedure and optimise patient’s outcome. In cases of uncertainty, when pleomorphic adenoma could not be ruled out with FNAC or core biopsy, the tumour should be excised.

With our case, we hope to expand the clinical knowledge of nodular fasciitis in the submandibular gland and highlight the importance to differentiate between pleomorphic adenoma and nodular fasciitis. It is important to consider nodular fasciitis as a possible diagnosis of a benign lesion in the submandibular gland, if the tumour display similar features, despite it being rare. This is due to the difference in their management.