Pleomorphic adenoma
Template:DiseaseDisorder infobox
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Overview
Pleomorphic adenoma is a benign neoplastic tumour of the salivary glands. It is the most common type of salivary gland tumour and the most common tumour of the parotid gland. It derives its name from the architectural pleomorphism (variable appearance) seen by light microscopy. It is also known as "Mixed tumor, salivary gland type", which describes its pleomorphic appearance as opposed to its dual origin from epithelial and myoepithelial elements.
Clinical Presentation
The tumour is usually solitary and presents as a slow growing, painless, firm single nodular mass. Isolated nodules are generally outgrowths of the main nodule rather than a multinodular presentation. It is usually mobile unless found in the palate and can cause atrophy of the mandibular ramus when located in the parotid gland. When found in the parotid tail, it may present as an eversion of the ear lobe. Though it is a benign tumour, pleomorphic adenomas have the capacity to grow to large proportions.
==Diagnosis== The diagnosis of salivary gland tumors utilize both histopathological sampling and radiographic studies. Histopathological sampling procedures include fine needle aspiration (FNA) and core needle biopsy (bigger needle comparing to FNA). Both of these procedures can be done in an outpatient setting. Diagnostic imaging techniques for salivary gland tumors include ultrasound, computer tomography (CT) and magnetic resonance imaging (MRI). Fine needle aspiration biopsy (FNA), operated in experienced hands, can determine whether the tumor is malignant in nature with sensitivity around 90%[1][2]. FNA can also distinguish primary salivary tumor from metastatic disease. Core needle biopsy can also be done in outpatient setting. It is more invasive but is more accurate compared to FNA with diagnostic accuracy greater than 97%[3]. Furthermore, core needle biopsy allows more accurate histological typing of the tumor. In terms of imaging studies, ultrasound can determine and characterize superficial parotid tumors. Certain types of salivary gland tumors have certain sonographic characteristics on ultrasound[4]. Ultrasound is also frequently used to guide FNA or core needle biopsy. CT allows direct, bilateral visualization of the salivary gland tumor and provides information about overall dimension and tissue invasion. CT is excellent for demonstrating bony invasion. MRI provides superior soft tissue delineation such as perineural invasion when compared to CT only[5]. Histologically, it is highly variable in appearance, even within individual tumours. It is characterized by an admixture of epithelial and myoepithelial elements in a variable background stroma that may be mucoid, myxoid, cartilaginous or hyaline. Epithelial elements may be arranged in duct-like structures, sheets, clumps and/or interlacing strands and consist of polygonal, spindle or stellate-shaped cells (hence pleomorphism). Areas of squamous metaplasia and epithelial pearls may be present. The tumour is usually enveloped by a fibrous capsule of varying thickness and often incomplete. The tumour often extends through these discontinuities but is not a sign of malignant transformation as it does not invade surrounding tissues.
Treatment
Treatment is by surgical excision with a margin of normal healthy tissue. Recurrences are rare unless treated too conservatively i.e. enucleation can lead to spillage and seeding of tumour cells.
See also
- Warthin's tumor - monomorphic adenoma
External links
- ↑ Cohen EG, Patel SG, Lin O; et al. (2004). "Fine-needle aspiration biopsy of salivary gland lesions in a selected patient population". Arch Otolaryngol Head Neck Surg. 130 (6): 773–8. doi:10.1001/archotol.130.6.773. PMID 15210562. Unknown parameter
|month=ignored (help) - ↑ Batsakis JG, Sneige N, el-Naggar AK (1992). "Fine-needle aspiration of salivary glands: its utility and tissue effects". Ann Otol Rhinol Laryngol. 101 (2 Pt 1): 185–8. PMID 1739267. Unknown parameter
|month=ignored (help) - ↑ Wan YL, Chan SC, Chen YL; et al. (2004). "Ultrasonography-guided core-needle biopsy of parotid gland masses". AJNR Am J Neuroradiol. 25 (9): 1608–12. PMID 15502149. Unknown parameter
|month=ignored (help) - ↑ Białek EJ, Jakubowski W, Karpińska G (2003). "Role of ultrasonography in diagnosis and differentiation of pleomorphic adenomas: work in progress". Arch Otolaryngol Head Neck Surg. 129 (9): 929–33. doi:10.1001/archotol.129.9.929. PMID 12975263. Unknown parameter
|month=ignored (help) - ↑ Koyuncu M, Seşen T, Akan H; et al. (2003). "Comparison of computed tomography and magnetic resonance imaging in the diagnosis of parotid tumors". Otolaryngol Head Neck Surg. 129 (6): 726–32. doi:10.1016/j.otohns.2003.07.009. PMID 14663442. Unknown parameter
|month=ignored (help)