Histological diagnosis
Case 117
【Progress】Biopsy of oral palate tumor depicted pleomorphic adenoma. He underwent surgical resection of the tumor. A few days after, he was discharged without any complications. He was scheduled to come to our hospital for periodic follow-up.
【Discussion】
Pleomorphic adenoma is known to arise from salivary glands such as parotid gland, submandibular gland, sublingual gland and minor salivary glands. Oral palate composes of soft palate and hard palate. Irrespective of soft and hard palate, there is a large number of minor salivary glands in there. Pleomorphic adenoma is a slow growing and benign tumor and the most common of all oral palate tumors and of all salivary gland tumors (60%) (1-4). Microscopically, it includes epithelial and mesenchymal elements which is, also termed as a mixed tumor.
Most of the pleomorphic adenoma are demarcated macroscopically from the surrounding by fibrous capsule and present as submucosal tumor. When the tumor is small, the cutting surface is homogeneous and as it grows larger, it becomes heterogeneous which indicates degeneration and necrosis(1-5). Moreover, it can erode hard plate in a small percentage, mimicking malignant tumor (5). In this situation, it is difficult to differentiate from muco-epidermoid carcinoma which is most of the oral malignant tumors. In our case, CT showed heterogeneous mass with erosion of the hard plate and growing to nasal lumen. Then, before biopsy, this tumor was clinically thought to be more malignant rather than benign.
Meanwhile, CT showed the presence of bulky calcification in the tumor, mimicking benign. Microscopically, pleomorphic adenoma manifest calcification with calcified or ossified degeneration. Bulky calcification in polymorphic adenoma is not common, but it incidentally occurs in the literature (6).
Both CT and MRI were conducted in our case. Both are useful to detect three-dimensional extent of the tumor (5). However, CT was superior to MRI in detecting bone erosion of the tumor and presence of calcification in the tumor. MRI with diffusion was expected to differentiate benign from malignancy, but enough signals were not gained for differentiation. This is simply because MRI is weak to detect tumors adjacent to air such as lung tumors and thyroid tumors.
Because pleomorphic adenoma from minor salivary glands are reported to have propensity for malignant transformation and enucleation alone often recurs, wide excision is required (1-5). In case of erosion to hard plate and /or maxillary bone, bone reconstruction is supplied. Our case received hard plate reconstruction accompanied with self-granulation and heal.
【Summary】
We present a seventy two-year-old male with pleomorphic adenoma with massive growth and erosion to bone mimicking malignancy originated from minor salivary glands of hard plate. It is borne in mind that there is a large number of minor salivary glands, irrespective in oral hard and soft palate, pleomorphic adenoma occurs most of the oral palate tumors and muco-epidermoid carcinoma does most of the oral palate malignant tumors. When pleomorphic tumor grows, it becomes heterogeneous indicating degeneration and necrosis with bulky calcification and erosion to hard plate and/or maxillary bone. CT is superior to MRI simply because hard palate is adjacent with air space and in the respects of detecting bone erosion of the tumor and presence of calcification in the tumor.
【References】
1.Ethunandan M, et al. Atypical features in pleomorphic adenoma: A clinicopathological study and implication for management. Int J Oral Maxillofac Surg. 2006;35(12):608–12.
2.Sreenivas DS. Pleomorphic adenoma of the palate: A case report. J Indian Dent Assoc. 2011;5:557–558.
3.Jorge J, et al. Juvenile intraoral pleomorphic adenoma: report of five cases and review of the literature. Int J Oral Maxillofac Surg. 2002;31:273–275. doi: 10.1054/ijom.2002.0206
4.Hmidi M, et al. Pleomorphic adenoma of the soft palate: major tumor in a minor gland
Pan Afr Med J. 2015; 22: 281. Published online 2015 Nov 23. doi: 10.11604/pamj.2015.22.281.5227
5.Patigaroo, SA. Pleomorphic Adenoma of Hard Palate: An Experience. J Maxillofac Oral Surg. 2014; 13: 36–41.
6.Shi, H, et al. Pleomorphic Adenoma with Extensive Ossified and Calcified Degeneration: Unusual CT Findings in One Case. American Journal of Neuroradiology April 2008, 29 (4) 737-738
2018.8.22