A Rare Lesion at Rare Location: A Surgeon’s Enigma

Abstract

Leiomyosarcoma of palate is a rare malignant spindle cell tumour in oral cavity. It is often misdiagnosed with other benign lesions like nodular fasciitis, clinical and histological similarity of rapid growth, rich cellularity, as the pathogenesis is unknown, which can make diagnosis and management challenging. The non-specific clinical, radiologic and pathological presentation of spindle cell tumours causes diagnostic difficulty due to similarities to granulation tissue, benign or malignant lesions in histologic and imaging features. Nevertheless, differentiation is important because the prognosis and treatment varies according to the type of tumor. NF is frequently evaluated by biopsy and also immunohistochemistry (IHC) which is very essential in cases of non-regressing lesions after biopsy. The present case report highlights the clinical and histopathologic challenges in a rare case of nodular fasciitis in the palate which initially diagnosed as granulation tissue and later confirmed as Grade l leiomyosarcoma on IHC.

Introduction

Spindle cells are of mesenchymal origin and form the body connective tissue, fat, muscle, bone, cartilage and blood vessels. Soft tissue spindle cell neoplasm may range from reactive lesions to benign and malignant tumours. Reactive to benign lesions are NF, fibromatosis, neurofibroma, leiomyoma, proliferative myositis and granulation tissue.

Amongst the malignant tumours are rhabdomyosarcoma, fibrosarcoma, leiomyosarcoma and liposarcoma [1]. They are quite rare in the oral cavity, less than 1% of all the tumours of oral origin. The vast appearances and architectural patterns of the spindle cell tumours make the distinction from similar microscopic lesions quite puzzling [2]. The aetiology is unknown for most benign and malignant soft tissue tumours.

In rare cases, genetic and environment, viral infections, irradiation and immune deficiency have been found related to the development of malignant soft tissue tumours like leiomyosarcoma as it arises from undifferentiated pluripotent undifferentiated mesenchymal cells. Although they have non-specific clinical presentation, those presenting with greater than 5 cm and deep seated have high risk of being a malignancy [3]. Nodular fasciitis (NF) is defined by the World Health Organization as a benign and reactive fibroblastic growth extending from the superficial fascia into the subcutaneous tissue or muscle was first described by Konwaler et al. as subcutaneous pseudo sarcomatous fibromatosis [4].

NF, as per histology, has been classified by Price et al. in three categories, myxomatous, intermediate and fibromatous [5]. NF has two important features which are simulation of appearance of sarcoma and the presence of inflammatory stigmata which lead Strout to refer it as pseudosarcomatous fasciitis [6]. The above-stated features often confuse the histopathologist between granulation tissue as reactive lesion, benign and malignant spindle cell tumours due to its fast growth, rich cellularity and mitotic activity [7]. This case report highlights the non-specific clinical presentation and diagnostic difficulties of NF of the palate which later diagnosed as Grade l leiomyosarcoma.

Case Report

A 45-year-old male, farmer by profession, presented with an intraoral swelling over left palatal region for 6 months. The growth was noticed by the patient while chewing food. The swelling extended from canine to second molar 3.5 cm × 4.2 cm in maximum size, not crossing the midline over the palate with overlying ulcerated red and white mucosa (Fig. 1).

Fig. 1.

Clinical view of palatal growth

There was no pain, bleeding or signs of paraesthesia or anaesthesia; however, the patient noticed some amount of pain during smoking. The patient gave a positive history for chronic exposure to tobacco, both in the form of smokeless and smoke. The medical history and dental history were insignificant. On systemic examination, clinically and radiographically, neck and chest were normal.

No intraoral sign of any odontogenic infection, extraoral signs of soft tissue growth or bony expansion, lymphadenopathy were found on clinical examination. Routine blood investigations were within normal limits. Contrast CT revealed erosion of palatal bone over left side abating maxillary sinus, not involving it (Fig. 2). Alternative diagnosis of pleomorphic adenoma, low-grade mucoepidermoid CA and neurofibroma was thought to be.

Fig. 2.

CECT coronal view

An incisional biopsy was performed under local anaesthesia for histopathological evaluation. After biopsy, no increase or decrease in palatal growth was found after 20 days. On histopathological examination, it was diagnosed as a granulation tissue. On second opinion, a probable diagnosis of nodular fasciitis (Fig. 3) with differential diagnosis of benign mesenchymal tumour was found.

Fig. 3.

NODULAR FASCITIS and IHC confirming Grade l Leiomyosarcoma Cells are arranged in interlacing fascicles (A), storiform pattern and lying loosely in haphazard manner (B). Entrapped salivary glands (C), IHC showing immunopositive for Desmin (D), h-caldesmon (E), Actin (F) and Beta-catenin (G) in 40×

As palatal erosion with no decrease in swelling after biopsy, clinically and radiographically no sign of nodal metastasis, hence, wide excision was planned. Under aseptic protocol, intraoral partial maxillectomy with safe margin of 2 cm (Fig. 4) followed by reconstruction with temporalis myofascial flap was performed under general anaesthesia.

Fig. 4.

Resected specimen

Post-operatively, histopathology confirmed nodular fasciitis with differential diagnosis of low-grade sarcoma. On IHC, it was reported as leiomyosarcoma Grade l/3 as per FNCLCC Grading (Fig. 3). Chemotherapy was not advised since low-grade leiomyosarcoma (Grade 1) do not metastasize. The patient was advised strict follow-up and PET Scan, which he denied.

The patient maintained the initial follow-up regularly (Fig. 5), but later reported with the swelling over the palate, 1-year post-surgery (Fig. 6). FNAC suggestive of leiomyosarcoma and referred to oncology centre for workup and chemotherapy and radiotherapy. Unfortunately, we lost the further follow-up. On telephonic conversation, the patient was advised chemo and radiotherapy by medical oncologist.

Fig. 5.

Reconstruction with Temporalis myofascial flap (Post-op 3 months)

Fig. 6.

Post-operative 12-month follow-up (Recurrence)

Discussion

NF is commonly seen in upper and lower extremities with reported incidence of 7–20% in head and neck region, involving facial skin and parotid sheath which is commonly misdiagnosed as a sarcoma due to its accelerated growth [7]. Being an uncommon lesion in oral cavity, its reported incidence varies from 16.7 to 52.8% involving lip and buccal mucosa, respectively [8]. On English literature search, only single case of palatal involvement was found, and the present case seems to be second [9]. NF most commonly occurs between 20 and 40 years of age, with equal sex predilection and ranging from 4 to 10 mm in diameter [10]. Oral NF is commonly wrongly classified and inappropriately managed owing to its non-specific clinical presentation and histologic features like increased cellularity and mitotic activity.

During the previous decade, numerous authors have reported oral NF, and hence, it should be kept in mind as a differential diagnosis of oral soft tissue masses like fibroma, neurofibroma and leiomyosarcoma [11]. Although pathogenesis of this entity remains unknown, it appears that chemical carcinogens used in agriculture like herbicides, radiation and genetics seems to have aetiological role. The present case was farmer by profession with history of chronic tobacco exposure may be the precipitating factors [3]. CT scans and MRI reveal no specific features of NF except hyperintense homogenous lesion commonly associated with neurofibroma, sarcoidosis, aggressive fibromatosis, dermatofibroma, fibrosarcoma and malignant fibrous histiocytoma [12]. In the present case, lesion shows a homogenous mass with attenuation similar to that of fluid and associated erosion of underlying bone on CT scan which can be observed with the differential diagnosis mentioned above.

Radiographic evaluation of NF is not associated with bony erosion but was present in our case which is suggestive either of pressure resorption or any aggressive lesion. The reported efficacy of FNAC for NF has been poor and was inconclusive in the present study [13]. Failure in early diagnosis and incorrect diagnosis has been very well reported in the literature.

The present case was initially diagnosed as granulation tissue, and on second opinion, it was diagnosed as nodular fasciitis or benign mesenchymal tumuor. Partial excision of NF as mode of treatment is acceptable with reported low recurrence rate. According to the literature, nodular fasciitis has been found to regress or resolve after incisional biopsy or partial excision [7]. Failure of regression after 20 days of biopsy and erosion of the bone is likely to be associated with underlying malignancy.

Authors would like to draw attention that if after biopsy, a case of NF does not regress, it should be reinvestigated with IHC for sarcoma. IHC is considered to be mandatory for precise diagnosis and is characterized by positive staining for vimentin and smooth muscle actin which is muscle-specific [7]. As reported in the literature, spindle cells contain vimentin and actin but lack S-100, desmin and keratin protein.

The present case report highlights IHC immunopositive for desmin/h-caldesmon and immune negative for calponin and S-100 protein, whereas immunohistochemical profile of NF is positive for smooth muscle and muscle-specific actin and vimentin indicating myofibroblast differentiation and not for S-100 protein, desmin and keratin [7]. Leiomyosarcoma commonly originates from smooth muscle cells in the wall of blood vessels or may originate from undifferentiated mesenchymal cells.

In oral cavity, leiomyosarcoma can be either primary (de novo), as in our present case, or secondary (metastatic from other sites). Leiomyosarcoma commonly arises from the smooth muscles of the uterus and is rarely seen in oral cavity due to paucity of the smooth muscles. If it arises in oral tissues, source could be from smooth muscle of the arterial tunica media, the Morgagni foramen, the circumvallate papillae and pluripotential mesenchymal cells. A large series of 50 cases by Georgios et al. reported incidence of palatal leiomyosarcoma around 6% and tumuor size was between 1.5 and 5 cm [14]. The FNCLCC system is a score system, based on three parameters that is tumour differentiation, amount of tissue necrosis and mitotic rate.

According to FNCLCC grading system, Grade 1 is when sarcomas closely resembles normal adult mesenchymal tissue and treatment is wide surgical excision, no chemotherapy required (e.g. low-grade leiomyosarcoma), as in the present case. In Grade 2, deep-seated tumours larger than 5 cm require adjuvant chemotherapy, and Grade 3 chemotherapy is required as they metastasize to neck and chest [3]. Smaller lesions or low-grade sarcomas are fit for wide local excision with 2-cm cuff of surrounding fat and muscles, accompanied with the negative margin and adjuvant treatment is unnecessary. When lesion is large, greater than 5 cm, deep-seated (irrespective of size) or incomplete excision and poor local control require concomitant chemotherapy with high doses (45 Gy) of radiotherapy [15]. In present case, the size of the lesion was 4.2 cm in greatest dimension, margins were negative three-dimensionally, so wide excision alone was considered sufficient for Grade l leiomyosarcoma without post-operative adjuvant therapy. The anatomical location and quality of surgical margin are crucial factor for local recurrence and prognosis depends on anatomical location.

Sarcomas located in posterior regions of oral cavity, like posterior maxillary sinus, pterygoid plates, infratemporal fossa and condyle have chances of leaving behind the pathology [14]. As in the present case, lesion was located in posterior maxilla, close to the posterior palate and abutting the maxillary sinus, possible recurrence of lesion may occur despite it being Grade l leiomyosarcoma with negative surgical margins.

Recurrent tumours in posterior location are generally managed with the chemotherapy and radiotherapy for better survival rate [13]. The reported 5-year survival rate in local soft tissue sarcoma (Grade l leiomyosarcoma) is 90.8%, for Grade ll is 71.4% and 43.5% for Grade lll. [12]. Local recurrence and metastasis worsen the prognosis and survival. In present case, 9 months after chemotherapy and radiotherapy, the patient is doing well.

Conclusion

Oral lesions can be with wide variety of presentations from inflammatory, fibrous, benign, malignant to metastatic, putting clinicians in dilemma on diagnosing and treatment plan. Biopsy remains the mainstay for initial diagnosis. NF has been shown to regress after biopsy, if not, then it should raise the suspicion of underlying sarcoma and IHC should be considered. Authors through this present case report would like to draw the attention of surgeons, that Grade l leiomyosarcomas, irrespective of their size and negative margin, located in posterior regions of oral cavity should be considered for post-operative chemo and radiotherapy for disease-free survival.

Compliance with Ethical Standards

Conflict of interest

The authors declare that they have no conflict of interest.