Abstract
Alveolar soft part sarcoma (ASPS) accounts for less than 1% of all sarcomas. More frequently encountered within the lower limbs, the authors present a 24-year-old male with ASPS presenting as an asymptomatic swelling of the lateral tongue. At 12 months post wide local excision of the lesion, the patient remains well with no evidence of local or regional recurrence. Histological and immunohistochemical features are diagnostic of ASPS. Whilst rare, head and neck surgeons should be aware of ASPS as a potential cause of slow growing lesions, as early surgical resection is vital in view of the propensity for metastatic spread.
First described in 1952 by C hristopherson et al. alveolar soft part sarcoma (ASPS) is a highly vascular, malignant mesodermal tumour, accounting for less than 1% of all soft-tissue sarcomas . Presenting in adolescence or young adulthood, ASPS is most frequently encountered within the lower extremities where it typically presents as a slow growing mass within the thigh. With a slow, insidious growth, patients frequently present with a large mass and metastatic spread . The head and neck is the primary site for 27% of these tumours, with 5% being located within the lingual tissues. The authors present the case of a young adult presenting with ASPS of the lateral tongue in order to highlight the importance of early histological diagnosis of lesions within the oral cavity.
Case report
A 24-year-old male presented with a 6-week history of an asymptomatic slowly growing lesion of the left lateral tongue ( Fig. 1 ). His medical history included nephritic syndrome as a child. He was on no regular medication, was a smoker of 5 pack years, and consumed moderate amounts of alcohol (10–20 units/week).
On examination there was a soft fluctuant swelling palpable on the antero-lateral aspect of the tongue, approximately 10 by 8 mm in dimension. Systemic examination was unremarkable with no palpable lymphadenopathy. Routine haematology and biochemistry results were within normal limits. The clinical appearances of the lesion were suggestive of benign pathology, but histological confirmation was sought, and the patient proceeded to excision biopsy under local anaesthesia.
Histological analysis ( Figs. 2 and 3 ) demonstrated a solid proliferation of tumour cells with moderate to abundant eosinophilic cytoplasm and large vesicular nuclei containing prominent nucleoli. Immunohistochemistry showed strong staining for MyoD1, focal staining for muscle actin, with identification of diastase resistant, periodic acid-Schiff (PAS) positive granules and needle-shaped structures in the cytoplasm. There was evidence of vascular invasion. The histological features confirmed a diagnosis of ASPS.
Radiological tumour staging with computed tomography (CT) of the chest, magnetic resonance imaging (MRI) of the brain and oral cavity, and positron emission tomography (PET) CT, confirmed the absence of systemic spread.
Further wide local resection with a 1 cm margin was performed under general anaesthesia with reconstruction using a free mucosal graft in view of suggestion of a histological positive margin. A mucosal graft obtained from the buccal mucosa was used to minimize scar tissue at the site of excision, which may compromise early detection of local recurrence. Histological analysis of this tissue confirmed benign scar tissue only. Postoperative recovery was uneventful with full functional outcome in both speech and swallowing.
At 12 months follow up there is no evidence of local recurrence or distant metastatic spread. The patient remains under regular surveillance.
Discussion
ASPS is a rare malignant tumour with a peak incidence between the ages of 15 and 35 years , with lingual cases typically occurring in childhood . There is a female preponderance prior to the age of 30 years .
With a propensity for early metastatic spread, ASPS outside of the head and neck frequently presents late with a large mass, and deposits within the lung, bone and/or brain. Reported cases in the literature suggest that lingual ASPS occurs earlier and without distant spread. Case reports indicate that ASPS may occur in any of the lingual surfaces. F anburg -S mith et al. analysed the features of 14 cases of lingual ASPS in eight male and six female patients with a median age of 5 years. Of this group, the tumours were most frequently identified on the lateral aspect of the tongue. All tumours were intramuscular and generally circumscribed. Of the 10 patients with adequate follow-up records, one developed pulmonary metastasis at 3 years which was amenable to resection. Twenty-two cases in the literature between 1966 and 2003 were reviewed by do N ascimento S ouza et al. Of these, five involved the lateral tongue, with a maximum age at presentation of 25 years. All of these were treated with surgical excision, with or without adjuvant chemo/radiotherapy. Follow-up data ranged between 2 and 36 months, with two of the five patients developing local or regional recurrence.
The head and neck is one of the more frequent sites for primary ASPS, but the tongue may also be the site of metastatic deposits. P orter et al. reported a 25-year-old male presenting with metastatic ASPS of the left lateral tongue 3 years after resection of ASPS within the brachialis muscle. The patient rapidly succumbed to his disease.
Most reported cases of lingual ASPS are larger than 8 mm at presentation . The present case presented at a similar stage, and early histological diagnosis resulted in a decreased surgical procedure with preservation of function, minimal local morbidity, and reduced probability of metastatic spread.
Tumour size appears to correlate with prognosis. Disturbance in local function such as dysphagia, dysphonia or mild discomfort in association with government educational attempts to raise oral cancer awareness may impact upon the earlier presentation of patients with ASPS of the tongue compared with other regions.
Clinical findings, as in this case, may mimic benign pathology such as haemangioma or vascular malformation , particularly since the ASPS may have a blue hue and therefore histological confirmation is essential. Radiological investigation with CT and MRI may aid in differentiation. Contrast enhanced CT findings include a central area of low attenuation, suggesting the presence of necrosis or the appearance of skeletal muscle with peripheral enhancement on an unenhanced scan. MRI features are of signal intensity equal to, or slightly higher, than skeletal muscle on T1-weighted images with numerous voids, and high signal intensity on T2-weighted images with few voids.
The diagnosis of ASPS depends on histological findings. Microscopically it is characterized by large polyhedral cells separated by delicate vascular channels and bands of fine connective tissue that confer an organoid pseudoalveolar pattern to the tumour . The arrangement of compact cellular aggregates containing numerous vascular channels surrounded by connective tissue septa, or in alveolar form with a central space lacking organized material led to the term ‘soft part’ . The characteristic finding in ASPS is PAS-positive diastase-resistant crystals in the cytoplasm of tumour cell, identified in 80% of cases . The exact tissue derivation of ASPS remains uncertain, but immunohistochemical stains indicate a myogenic origin.
Complete surgical resection is the mainstay of treatment. Where excision biopsy has been performed for a seemingly benign process, further resection following histological diagnosis is advocated. Depending on the size of the resection, there are a number of reconstruction options available to the surgeon. The key benefit of a free mucosal graft, used in this case, is that surveillance is unhindered by florid scarring when examining and palpating the area. Other benefits include minimal donor site morbidity with good healing potential, and the similarity of tissue type with the recipient site. The main goal of intra-oral reconstructive procedures is to maintain function, and this has been satisfactorily achieved in this patient.
In contrast to the more frequently encountered malignant tumours of the head and neck, ASPS spreads via the haematogenous route. Lymph node involvement is seen in only 7% of cases, negating the need for routine neck dissection in most cases.
Adjuvant chemo/radiotherapy is largely limited to patients presenting with advanced disease, with further local resection being the preferred option in cases of involved margins. Radiotherapy of the head and neck, within the young patient groups affected by ASPS, has the potential to lead to significant morbidity including radiation-induced sarcoma and growth disturbance. Various chemotherapeutic agents have been tried with largely disappointing results.
Overall, the prognosis of ASPS is poor, although patients with primary lingual ASPS seem to fare better than those with lesions at other sites. Whilst free from disease at 12 months, the present patient requires an extended period of surveillance in view of the protracted course of malignant dissemination . Head and neck surgeons should be aware of ASPS as a potential cause of slow growing lesions, as early surgical resection is vital in view of the propensity for metastatic spread.
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