Diagnosis

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The Scar Solution By Sean Lowry

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The diagnosis of a tumor of the parotid gland will be dependent upon the history, clinical examination, imaging, and fine needle aspiration biopsy (FNAB). In most cases the history will be of a painless slow-growing lump that the patient had been aware of for some months or even years, and that was noticed initially when shaving, washing, or applying makeup. Occasionally the patient will report a rapidly growing mass, but this is not always a malignancy, as a long-standing retroman-dibular tumor that can no longer be accommodated in this space may have "popped out" and become prominent. Pain in a parotid mass is usually an ominous sign and can be an indication of adenoid cystic carcinoma. A history of facial nerve weakness, numbness of the ear or facial skin, or enlarged nodes in the neck are signs of malignancy.

Clinical examination will begin with the cervical nodes and palpation of the parotid. The facial nerve and muscles of facial expression are tested and intraoral examination of the soft palate and lateral pharynx is done to exclude deep lobe tumors extending into the parapharyngeal space. Most parotid tumors will present as smooth, sometimes lobulated, firm or hard nontender masses in the superficial lobe. Most are discrete and mobile. Fixation to the skin, ulceration, or deep muscle fixation are signs of malignancy. Facial nerve palsy and associated hard lymph nodes are also signs of parotid cancer. However, only 2.6-22% of parotid cancers will have VII nerve palsy (Ord 1995). Overall, 30% of malignancies are diagnosed on clinical features with palpable cervical nodes, facial nerve palsy, deep fixation, and rapid enlargement being significant signs (Wong 2001). The majority of cancers present clinically as benign tumors.

The differential diagnosis of a parotid tumor includes lesions arising outside the parotid as well as intra-parotid masses. Skin lesions such as sebaceous or dermoid cysts are usually distinguished by their superficial origin in the overlying skin. Neoplasms of the masseter and masseteric hypertrophy will become fixed and more prominent on clenching the jaws. Condylar masses usually move with jaw opening and jaw lesions are usually bony hard to palpation. Intra-parotid masses that mimic parotid tumors include enlarged parotid nodes, and, as these may be metastatic, clinical examination of the parotid mass should always include the ear and the scalp for skin cancers. Parotid cysts may be difficult to distinguish from common parotid tumors such as PAs and low-grade muco-epidermoid carcinoma, which can present as fluctuant cysts. Tumors arising in the parotid tail may be mistaken for submandibular or neck masses (Figure 8.1), while those arising in the accessory gland may be thought to arise in the cheek itself (Figure 8.2).

In imaging the parotid, technetium scans may confirm a diagnosis of Warthin's tumor or oncocytoma but are largely of historical interest. The same is true for sialography, which is no longer used for tumors. Ultrasound can distinguish cystic from solid masses and may be helpful to guide

FNAB; however, CT scanning or MR are the imaging modalities of choice if the clinician feels the information gained is worth the financial cost. Little is added to the diagnosis when imaging tumors in the superficial lobes; however, imaging deep lobe tumors, particularly those with para-pharyngeal extension, gives the surgeon useful information. Recent papers have claimed that highresolution MR using a surface coil may allow imaging of the facial nerve and its relationship to the tumor (Takahashi et al. 2005). Other methods of predicting facial nerve position include use of anatomic lines drawn on the images, such as the facial nerve line, which connects the lateral surface of the posterior belly of the digastric muscle with the lateral surface of the cortical bone of the ascending ramus of the mandible, and which has been assessed as 88% accurate in determining the location of the tumor in relation to the nerve (Ari-yoshi and Shimahara 1998). Another proposed guideline is the Utrecht line connecting the most

Images Scans The Neck With Lump
Figure 8.1a. A woman with Warthin's tumor in the parotid tail presenting as a neck mass.
Dense Parotid Mass
Figure 8.1b. CT scan confirms the mass is in the parotid tail.

Figure 8.1c. Surgical specimen following partial parotidectomy of parotid tail with tumor.

dorsal point visible of C1 or C2 vertebra to the retromandibular vein (RMV) (de Ru, Van Bentham, and Hordijk 2002). Magnetic resonance imaging may be helpful in distinguishing benign PAs from malignant tumors, by post-contrast enhancement, a higher T2 signal, and lack of invasion (Figure 8.2). However, Fee and Tran (2003) suggest that neither MR nor ultrasound is accurate enough to

Figures 8.1d and 8.1e. Low- and high-power microscopic views of specimen, which was a Warthin's tumor.

be routinely used in the workup of parotid masses and that careful history and examination are sufficient for most cases. This conclusion was echoed by de Ru, Maartens, and Van Bentham et al. (2007), who concluded that MRI and palpation are almost equally accurate for assessing tumor location and both are superior to ultrasound. They recommend the use of FNAB as an accurate method of assessing whether a tumor is malignant, and MR only for tumors in the deep lobe or malignant tumors. PET scan and fused PET/CT have so far not been shown to reliably differentiate between benign and malignant parotid tumors (Rubello, Nanni, and Castellucci et al. 2005).

FNAB may be utilized to give a preoperative cytologic diagnosis. Open biopsy is contraindi-cated, as it will cause spillage and seeding of d e a b

Minor Salivary Gland Tumor
Figures 8.2a and 8.2b. MR T1 and T2 weighted images of a cystic pleomorphic adenoma deep in the cheek is a diagnostic challenge as to whether this is a minor salivary gland tumor or an accessory parotid tumor.
Figure 8.2c. Clinically this lesion appears to be inferior to the parotid duct, as seen in the sagittal view, which would make an accessory lobe tumor unlikely.

benign PAs and lead to increased recurrence (Figure 8.3). Although FNAB will not usually change the proposed treatment plan of parotidec-tomy, a malignant diagnosis may allow better pre-surgical counseling for possible facial nerve sacrifice. In addition, when extracapsular dissection or limited superficial parotidectomy is contemplated (see below), it is best to have confirmation of the benign nature of the tumor (O'Brien 2003). There is still controversy whether FNAB is mandatory as part of the diagnostic workup for a presumed parotid tumor. Although Schroder, Eckel, and Rasche et al. (2000) report a sensitivity of 93.1%, specificity of 99.2%, and accuracy of 98.2%, other papers have shown lower figures, sensitivity 81.5% and specificity 97.5% (Longuet et al. 2001).

Zbaren, Schar, and Hotz et al. (2001) recommended FNAB as a valuable adjunct to preoperative diagnosis, reporting 86% accuracy, 64% sensitivity, and 95% specificity. However, in a study of 6,249 participant responses from the database of the College of American Pathologists Inter-laboratory Comparison Program in Nongynecologic Cytology, the sensitivity and specificity for interpreting salivary tumors as benign or malignant was 73% and 91%. Benign cases with the commonest false positive rates were monomorphic a b

Tattoo Croce Donna

Figure 8.3a. A 45-year-old woman with parotid pleomor-phic adenoma biopsied through the cheek. The arrow points to the biopsy scar.

Figure 8.3b. The surgical incision is delineated and includes a 1 cm skin paddle surrounding the biopsy scar.

Flug Larver

Figure 8.3c. Superficial parotidectomy with complete nerve dissection.

Salivary Gland Biopsy Results

Figure 8.3b. The surgical incision is delineated and includes a 1 cm skin paddle surrounding the biopsy scar.

Figure 8.3d. Surgical specimen of parotid with overlying skin.

Figure 8.3e. Histopathology confirms diagnosis of pleomorphic adenoma. Note marked pseudocapsule of collagenous tissue. The patient is disease free 10+ years post-surgery.

adenoma (53%) and intra-parotid lymph node (36%). Malignant salivary gland tumors with the highest false negative rate were acinic cell carcinoma (49%), low-grade mucoepidermoid carcinoma (43%), and adenoid cystic carcinoma (33%). It was felt the data confirmed the difficulty inherent in FNAB of salivary glands (Hughes, Volk, and Wilbur 2005). A paper from the Memorial Sloan Kettering Cancer Center concluded that an FNAB result positive for a malignant neoplastic process is generally predictive of the final histologic diagnosis, whereas the predictive value of a negative FNAB is low (Cohen, Patel, and Lin et al. 2004).

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