adenoid cystic carcinoma was first described by billroth in 1859 and called " cylindroma " due to its characteristic histologic appearance1 . in 1953 , adenoid cystic carcinoma is a malignant salivary gland tumour characterized by a deceptive histologic pattern , indolent , locally invasive growth with high propensity for perineural invasion , local recurrence and distant metastasis . these uncommon neoplasms account for fewer than 1% of all head and neck malignancies and fewer than 10% of all salivary neoplasms . they make up 15%-30% of submandibular gland tumours , 30% of minor salivary gland tumours , and 2%-15% of parotid gland tumors1 . it is defined by the world health organization as " a basaloid tumour consisting of epithelial and myoepithelial cells in various morphological configurations , including tubular , cribriform and solid patterns . the present case report is unique as it shows presentation of adenoid cystic carcinoma as a solitary ulcer on the floor of the mouth rather than the classical nodular swelling . a 56-year - old male patient presented with a chief complaint of an ulcer in the left floor of the mouth for one week . he gave a history of pain of respect on the left side of the jaw which was continuous , dull , throbbing , and radiating to the ear of the same side . the patient had under gone extraction for tooth # 18 but the pain still persisted . thereafter , he noticed an ulcer on the left floor of the mouth which was initially small and increased to the present size . there was no history of bleeding or discharge , but he did have difficulty eating and speaking . intraoral examination of the soft tissues , the buccal mucosa , labial mucosa , tongue , and palate showed no abnormalities , but there was a solitary ulcer on the left floor of the mouth . examination of gingival status revealed his oral hygiene status to be poor , with severe stains and calculus deposits . on hard tissue examination , healing socket was present in respect to tooth # 19 . on local examination of the lesion , inspectory findings revealed a solitary ulcer presenting as a mucosal tear involving the mucosa and connective tissue extending mesially from left side of the lingual frenum and distally to an area corresponding to the extracted tooth # 19 region . it was oval in shape , 32 cm at its widest point , and 3 cm deep . the margins were everted , the edges of the ulcer were sloping , and the floor was not evident . the colour was the same as that of the adjacent mucosa , but erythematous at the periphery of the ulcer . 1 ) on palpation of the site , the size and the extent of the ulcer were confirmed . the margins and the base of the ulcer were mildly indurated in a posterior aspect . based on the history given by the patient and the clinical features , a provisional diagnosis of carcinoma of the floor of the mouth t4an0m0 , chronic generalized periodontitis , partially edentulous in respect to tooth # 7 , # 5 , # 3 , # 13 , # 14 , # 15 , # 24 , # 19 , # 25 , and # 31 was made . lesions presenting as solitary ulcers on the floor of the mouth were considered in the differential diagnosis . traumatic ulcers are most common on the tongue , lips , mucobuccal fold , gingiva and palate . they present as solitary ulcers with raised reddish borders and white necrotic floors with associated history of trauma . on the floor of the mouth , they are usually due to calculus or sharp denture margins . major recurrent apthous ulcers are mostly solitary , deep , and painful , with smooth margins and a reddish halo and may persist for months with history of reoccurrences . habit associated lesions seen in quid chewers may also form ulcerations at the region of quid placement . odontogenic infections may be associated with an ulcer that may serve as a cloacal opening of a sinus draining a chronic alveolar abscess . other conditions such as acute necrotic ulcerative gingivostomatitis or gangrenous stomatitis usually present as necrotic sloughing ulcerative lesions diffusely involving the gingiva . solitary ulcers are also seen in nonodontogenic systemic diseases such as uncontrolled diabetes mellitus , blood dyscrasias ( leukemia , sickle cell anemia ) , gastrointestinal and immunocompromised individuals and autoimmune conditions ( pemphigus , pemphigoid , erythema multiforme , epidermolysis bullosa ) . the ulcers in such conditions are well demarcated , painful , and shallow with an erythematous halo and a grey necrotic floor , usually in the marginal and interdental gingiva . salivary gland disorders such as adenoid cystic carcinoma , mucoepidermoid carcinoma , mucous adenocarcinoma , warthin tumor and necrotising sialometaplasia are seen as solitary palatal ulcers . an orthopantomogram and a mandibular crossectional occlusal radiograph were taken and showed no abnormality in the region of interest.(fig . 2 ) a magnetic resonance image was taken , and the axial sections showed a t1-weighted image of a mass of medium intensity extending from the midline of the mandible to the premolar region on the left side.(fig . 3 ) an incisional biopsy was performed and the histopathologic report showed the presence of uniform basaloid cells arranged in the form of solid islands , along with a cribriform pattern at some places . based on the clinical features and the histopathologic report , a final diagnosis of adenoid cystic carcinoma t4an0m0 was made.(fig . adenoid cystic carcinoma is a malignant tumour with a deceptively benign histological appearance , characterized by indolent locally invasive growth with a high propensity for local recurrence and distant metastasis . according to the literature gender predilection is an inconsistent feature in the literature ; however , it is slightly more common in women than in men4,5 . although the palate is the most commonly involved intraoral site , other commonly involved areas are the major and minor salivary gland regions , the floor of the mouth , the tongue and the gingiva ( in decreasing order ) . adenoid cystic carcinoma usually presents as a slowly growing , firm , unilobular mass in the glands . however , in our case it presented as a solitary ulcer on the floor of the mouth . the clinical course is characterized by an initial period of slow and indolent growth that is usually asymptomatic , although bone invasion or perineural spread can cause pain or hypoesthesia5 . adenoid cystic carcinoma of the salivary glands is a malignant epithelial tumour with bidirectional differentiation towards luminal ( ductal ) and abluminal ( myoepithelial and basal ) cells . the tumour is composed of basaloid cells with small , angulated , and hyper chromatic nuclei and scant cytoplasm arranged into three prognostically significant patterns : cribriform , tubular , and solid . the combination of surgery and postoperative radiation therapy has improved locoregional control of the disease . despite this achievement , late local recurrence and distant metastasis rates remain high and may occur decades after initial diagnosis5 . in its most frequently seen histological pattern , the majority of the cells are small and darkly stained with scant cytoplasm . the cells are arranged in nests or sheets that are fenestrated by round or oval spaces , creating the characteristic " cribriform " design . occasionally , the tumours have a predominantly solid cellular growth with a basaloid or anaplastic appearance that has few , if any , fenestrations . tubular structures with minimal stratification of the lining epithelium are often mixed with the classic cribriform and solid areas6 . several authors have suggested that a solid histological pattern indicates a more serious prognosis than a cystic pattern . stewart7 first noted the increased aggression suggested by the solid variant , although he credits the initial observation to patey and thakray8 . little information exists on cytogenetic abnormalities in salivary gland neoplasms , but in adenoid cystic carcinoma , anomalies in the terminal part of the 6q and 9p chromosomes have been reported . recent studies have demonstrated a high incidence of loss of heterozygosity at chromosome 6q23 - 359 . the differential diagnosis of adenoid cystic carcinoma in cludes tumours that also exhibit tubular and cribriform structures , such as polymorphous low - grade adenocarcinoma , tumours with basaloid cellular morphology , such as basal cell adenoma , and basal cell adenocarcinoma and tumours with a dual population of ductal and myoepithelial cells , such as pleo morphic adenoma8 . possible treatments of adenoid cystic carcinoma include four different modalities : surgical therapy , radiotherapy , chemotherapy and combined therapy . avery et al.11 recommend postoperative radiation since radiation often produces tumour regression and relieves symptoms . postoperative radiotherapy is also indicated when the tumour location is close to the base of the cranium with the presence of neck lymph node metastasis and perineural invasion , with a solid histological subtype , and for recurrent tumours11 . adenoid cystic carcinoma shows a limited response to chemotherapy , and it is believed that this lack of a response is due to its slow growth rate . however , a study by alcedo et al.12 opened up a new possibility in the pharmacological treatment of this tumour by demonstrating its response to imatinib mesylate , a potent inhibitor of kit gene tyrosine kinase , which is an enzyme involved in the pathogenesis of the tumour . however , more studies are needed to confirm its effectiveness . distant metastasis can occur even decades after the primary tumour has been treated and after having achieved adequate locoregional control . furthermore in the setting of inoperable , incompletely resected or recurrent tumours , outcomes after conventional therapy are dismal and remain a therapeutic challenge . some authors have applied other forms of radiotherapy , particularly neutron irradiation , aiming to improve treatment results13 . however , adenoid cystic carcinoma remains incurable because further improvements in local - regional control are not likely to impact survival due to the high number of distant failures . the present case differs from usual cases of adenoid cystic carcnioma with respect to site and presentation , making it a rare entity . thus , the aim of this article is to emphasise that though the literature states that adenoid cystic carcinoma ulcerates the superficial lesional mucosa , it can also present as an ulcerative lesion .
adenoid cystic carcinoma is a rare epithelial tumour , and comprises about 1% of all malignant tumours of the oral and maxillofacial region . 
 it is a malignant tumour which may develop in the trachea , bronchus , lungs or mammary glands , in addition to the head and neck region . 
 occurrences in the head and neck are mostly detected in the major salivary gland , oral cavity , pharynx and paranasal sinus where it presents as a slow growing firm nodular swelling . 
 the aim of the article is to highlight the unique presentation of adenoid cystic carcinoma as a solitary ulcer on the floor of the mouth .