Abstract
Basal cell adenocarcinoma (BCAC) is a rare malignant neoplasm in the salivary glands and BCAC of the minor salivary glands is exceedingly rare. Only nine cases of palatal BCACs of the minor salivary gland have been reported. BCAC is a low-grade malignant tumour which shares many histologic characteristics with basal cell adenoma. Histological differentiation between the two is difficult and they are often discriminated only by invasion of local structures or by perineural or vascular invasive figures. The authors describe the case of a 69-year-old man with a massive BCAC of a palatal minor salivary gland that progressed into the nasal cavity and pterygopalatine fossa and was treated by a subtotal maxillectomy. This is a highly locally advanced case which required a wider surgical excision range than other previously reported BCAC cases of the palatal minor salivary glands. In this case, the proper diagnosis could not be made by local biopsy alone. It should be kept in mind that it may be difficult to distinguish BCAC from basal cell adenoma by microscopic examination of biopsy specimens alone.
Basal cell adenocarcinoma (BCAC) is a rare salivary gland tumour, comprising 3% of all malignant salivary neoplasms . BCAC predominantly affects the parotid or submandibular gland, and BCAC occurring from the minor salivary gland is exceedingly rare. BCAC of the minor salivary gland has been reported in very few cases since it was first reported in 1992 . In the present report, the authors describe the case of a massive BCAC arising from the palatal minor salivary gland that progressed into the maxillary sinus, nasal cavity and pterygopalatine fossa.
Case report
A 69-year-old man was referred to the authors’ department in May 2010 for a tumour in his right nasal cavity. A few days before presentation, he had consulted an otolaryngologist for right nasal obstruction and a right nasal tumour was identified. Symptoms, such as epistaxis and pain were absent. The patient was a deaf–mute and illiterate, so communication was limited to sign language. Anterior rhinoscopy revealed a red smooth mass in the right nasal cavity and an ulcerating mass was observed outside of the right upper gingiva ( Fig. 1 ). No other specific findings were observed in his head and neck region. Enhanced computed tomography (CT) showed a homogenous mass infiltrating the palate, nasal cavity, right maxillary sinus and right pterygopalatine fossa with almost no enhanced effect ( Fig. 2 ). Bony resorption of the palate and maxillary sinus wall (medial, lateral and bottom) was observed. T1-weighted gadolinium (Gd) enhanced magnetic resonance imaging (MRI) showed an isointense tumour with a moderately enhanced effect. The palate-occupying tumour was 4.0 cm × 2.5 cm and the connective pterygopalatine fossa-occupying tumour was 3.1 cm × 2.3 cm. The lesion was relatively well demarcated, and pterygoid muscle was displaced ( Fig. 2 ). A biopsy was performed using the Caldwell-Luc method under general anaesthesia, and showed a solid mass overlying the maxillary mucosa to the nasal cavity. Pathological findings showed a tumour consisting of extensive basaloid cells with eosinophilic cytoplasm, exhibiting trabecular and tubular features. A small mitotic activation area was revealed, but no clear figure of microinvasion into the adjacent soft tissue was observed. Immunohistochemical examinations showed a small number of p53-positive cells, and the Ki-67-positive index was 10%. At this time, the diagnosis was basal cell adenoma (tubulotrabecular type). Observation was the management selected initially because the patient was asymptomatic and did not consent to radical surgery. After 2 months, mass enlargement was observed in the right nasal cavity, and the patient developed faint cheek pain; he agreed to undergo radial surgical therapy.
At surgery, the maxilla was approached using a Weber-Ferguson incision and a subtotal maxillectomy was performed. The resection area included the right hard palate, zygomatic arch, coronoid process, maxillary posterior wall, part of the nasal septum, and the pterygoid process. The maxillary defect was reconstructed with a fascia lata musculocutaneous flap ( Fig. 3 ).
Microscopic examination showed a mainly pseudoencapsulated tumour that was strikingly similar to a basal cell adenoma. The neoplastic cells were basaloid cells and were different types of tumour cells, with a solid growth pattern and tubulotrabecular pattern. In some areas, the tumour showed invasion of the adjacent soft tissues and bone tissue, but marked vascular invasion was not observed. Although tumour invasion into the pterygoid process was revealed, all surgical margins were negative. A final diagnosis of basal cell adenocarcinoma was made ( Fig. 4 ). Postoperatively, the patient’s course was uneventful, and there have been no signs of local recurrence or distant metastasis during the 8-month follow-up.
