Abstract
The authors report a case of adenoid cystic carcinoma (ACC) complicated with sialolithiasis of the submandibular gland. The patient was a 43-year-old female with a history of papillotubular carcinoma of the breast almost at the same time. She had noticed a swelling in her sublingual area for 10 years, which was later diagnosed by her dentist to be due to a sialolith in the left submandibular gland. After several years of observation, the patient was referred to have her left submandibular gland, containing the stone, surgically removed with a diagnosis of atrophic sialadenitis. Histopathologically, the submandibular gland was extensively replaced with fibrous granulation tissue, in which there were small but invasive foci of ACC. The present case indicates that ACC could arise in the background of chronic sialadenitis. It is suggested that long-standing sialadenitis cases should be carefully examined to exclude suspicion of malignancy before surgery.
Little is known about the pathogenesis or etiology of salivary gland tumors, although the authors have demonstrated the role of radiation in Warthin’s tumors and mucoepidermoid carcinoma and Epstein–Barr viruses in lymphoepithelial carcinoma . These examples with obvious causative factors are exceptional and limited in number among salivary gland tumors. It is therefore necessary to seek and document cases that seem to have possible causative backgrounds, especially those of common salivary gland tumors, other than those mentioned above, such as pleomorphic adenoma or adenoid cystic carcinoma (ACC) .
The purpose of this report is to document a rare case of ACC in the submandibular gland of a 43-year-old female patient who had been suffering from sialolithiasis-related sialadenitis of the same gland for 10 years, to cast some light on the pathogenetic background of ACC and to suggest the necessity of undertaking full clinical and radiographic examinations to exclude suspicion of malignancy before surgery. The authors have found only one case of such a complication of ACC and sialolithiasis in the literature .
Case report
A 43-year-old female was referred with painless swelling in her sublingual area for 10 years. Although her dentist had diagnosed a sialolith in the left submandibular gland by panoramic radiography, the patient chose to forego treatment of the lesion because of its indolent symptom progression. On clinical examination, she had a discharge of pus from the opening of the Wharton’s duct in the floor of the mouth. Both plain X-ray and computed tomography (CT) in bone window ( Fig. 1 a ) examinations revealed a calculus, measuring about 5 × 5 × 10 mm in size, in the distal end of the Wharton’s duct at the hilar area of the left atrophic submandibular gland. In addition, another small sialolith was revealed within the left submandibular gland in the frontal section of the CT in soft tissue window examination ( Fig. 1 b). Following a clinical diagnosis of atrophic sialadenitis due to sialolithiasis, the submandibular gland containing the stone was surgically removed under general anesthesia. The sialolith was confirmed to be located at the distal end of the Wharton’s duct and was removed separately from the gland. The patient has been free of disease for 5 years since surgery.
The surgically removed left submandibular gland was irregularly shaped, measuring 32 × 30 × 20 mm in size, and was covered with rough surfaced fibrous connective tissue. On the cut surface, the lobular structures of the salivary gland had been replacement with fibrous granulation tissue or adipose tissue, and it was diagnosed as non-specific chronic sialadenitis ( Fig. 2 a ). The salivary stone, measuring 8 × 6 × 6 mm in size, was demineralized, and its cut surface showed a concentric lamellar structure. Histologically, the submandibular gland was extensively atrophic and replaced with fibro-adipose tissues containing some traces of lobular structures scattering minimal ductal elements ( Fig. 2 a). The Wharton’s duct ( Fig. 2 a, arrow; Fig. 2 b, asterisk) was surrounded by thick fibrous granulation tissue, in which small but invasive foci of ACC ( Fig. 2 b) were scattered. Most of the ACC cell nests showed characteristic cribriform patterns ( Fig. 2 c) with perineural invasion. The ACC foci had no capsule but were well demarcated from the surrounding submandibular tissue with extensive fatty changes ( Fig. 2 d).
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