Fine-needle aspiration (FNA) has been used increasingly

Worrisome Histologic Alterations Following Fine-Needle Aspiration of Benign Parotid Lesions Shiyong Li, MD, PhD; Zubair W. Baloch, MD, PhD; John E. Tomaszewski, MD; Virginia A. LiVolsi, MD Objective. To describe the histologic changes associated with preoperative fine-needle aspiration biopsies of benign parotid lesions and the features that distinguish these changes from malignant neoplasms. Materials and Methods. Ten benign parotid lesions with a recent history of preoperative fine-needle aspiration were selected, including pleomorphic adenoma (4 cases), oncocytic adenoma (3 cases), myoepithelioma (1 case), Warthin tumor (1 case), and lymphoepithelial cyst (1 case). Results. A spectrum of histologic alterations were observed. Alterations included squamous cell metaplasia (8 cases), infarction and necrosis (4 cases), subepithelial stromal hyalinization (3 cases), acute and chronic hemorrhage and inflammation with multinucleated giant cells (all cases), granulation tissue with subsequent fibrosis (all cases), cholesterol cleft formation (1 case), pseudoxanthomatous reaction (1 case), pseudocapsular invasion (1 case), and microcystic degeneration (2 cases). In cases with exuberant squamous metaplasia, necrosis, or subepithelial stromal hyalinization, a diagnosis of squamous cell carcinoma or low-grade mucoepidermoid carcinoma was seriously considered. Conclusions. Knowledge of a previous fine-needle aspiration procedure and awareness of its effects on histology of the subsequent parotidectomy specimens are necessary to avoid potential misdiagnosis. (Arch Pathol Lab Med. 2000;124:87 91) Fine-needle aspiration (FNA) has been used increasingly as a diagnostic procedure to evaluate neoplastic and nonneoplastic lesions in various tissues, as well as to assist in preoperative management. It has proven to be a rapid, reliable, safe, and well-tolerated method with few complications. Although a variety of atypical histologic changes have been well documented in thyroid, breast, and lymph node tissues following FNA, 1 4 only a few case reports have described infarction and necrosis of benign salivary gland neoplasms secondary to FNA. 5 8 In this article, we report the histologic alterations noted following FNA in 10 benign parotid lesions and discuss the potential problems in distinguishing these FNA-associated effects from malignant neoplasms. MATERIALS AND METHODS The surgical pathology database from 1993 to mid-1998 in the Department of Pathology at the University of Pennsylvania Medical Center (Philadelphia, Pa) was searched for benign parotid lesions with a recent history of preoperative FNA prior to surgical resection. Of the 44 cases retrieved, 7 were found to have FNA-associated histologic alterations that warranted a review at our surgical pathology consensus conference. Three additional cases came from one of the authors personal consultation files (V.A.L.). All surgical specimens were fixed in formalin and ex- Accepted for publication May 27, 1999. From the Department of Pathology and Laboratory Medicine, University of Pennsylvania Medical Center, Philadelphia, Pa. Presented in part at the XXII International Congress of the International Academy of Pathology and 13th World Congress of Academic and Environmental Pathology, Nice, France, October 1998. Reprints: Virginia A. LiVolsi, MD, Department of Pathology and Laboratory Medicine, University of Pennsylvania Medical Center, 6 Founders, 3400 Spruce St, Philadelphia, PA 19104. amined with hematoxylin-eosin stain. In addition, mucicarmine stain was performed in some cases. The FNA procedure for the University of Pennsylvania Medical Center cases was performed using a 22- or 23-gauge needle with a syringe attached to a commercially available syringe holder. The average number of passes was 2 to 3. In one of the consultation cases, a 23-gauge needle was used. The size of needle used in the remaining 2 consultation cases was unknown. The clinical data and histologic diagnoses for each patient are listed in Table 1. RESULTS As shown in Table 1, the patients in this study included 4 men, 5 women, and 1 girl; their ages ranged from 12 to 78 years (average, 54 years). The duration between FNA and surgical resection was 4 days to 3 months, with an average range of approximately 3 weeks. The underlying lesions were pleomorphic adenoma (benign mixed tumor, 3 cases), oncocytic adenoma (3 cases, all of which were consultation cases), monomorphic adenoma (1 case), myoepithelioma (1 case), Warthin tumor (1 case), and benign lymphoepithelial cyst in a patient positive for human immunodeficiency virus (1 case). The size of these benign lesions varied from 0.8 to 4.0 cm (mean, 2.0 cm), and all lesions were well circumscribed and encapsulated. A representative cut section of pleomorphic adenoma with extensive necrosis (case 1) is shown in Figure 1. The histologic changes due to FNA are summarized in Table 2. Squamous cell metaplasia was seen in 8 of the 10 cases. The metaplastic change was either focal or extensive, and the latter was associated with severe infarction and necrosis (2 oncocytic adenomas and 1 pleomorphic adenoma) or significant subepithelial stromal hyalinization (1 oncocytic adenoma). The metaplastic squamous epithelium was arranged in small islands or large masses in an arcadelike or cordlike pattern, grew in a stellate fashion Arch Pathol Lab Med Vol 124, January 2000 Alterations Following FNA of Benign Parotid Lesions Li et al 87

Table 1. Summary of the Patients Clinical Data and Histology of the Benign Parotid Lesions Case No. Age, y/sex Anatomic Location Diagnosis 1 2 3 4 5 6 7 8 9 10 37/M 78/F 66/F 60/F 71/F 50/M 12/F 54/M 67/F 43/M Myoepithelioma Monomorphic adenoma Warthin tumor Lymphoepithelial cyst Size of Lesion, cm 2.0 1.6 2.5 2.2 0.8 4.0 3.0 Time Interval Between Surgery and FNA 2 3 wk 2 3 wk 3wk 3mo 10 d 25 d 4d Case No. 1 2 3 4 5 6 7 8 9 10 Table 2. Histologic Alterations Following Fine-Needle Aspiration of Benign Salivary Gland Lesions* Squamous Metaplasia Subepithelial Hyalinization Infarction With Necrosis Fibrosis and Hemorrhage * The histologic alterations are graded from extensive () to focal (). Minus sign indicates case was negative for that alteration. Other column includes chronic inflammation, multinucleated giant cells, pseudocapsular invasion, cholesterol clefts, pseudoxanthomatous reaction, or microcyst formation. Other in a chondromyxoid background or fibroblastic stroma, and showed focal keratinization (Figures 2 and 3). The metaplastic areas were found parallel and adjacent to the central necrotic areas if necrosis was present (Figure 4). Surrounding the nests of squamous epithelium were the underlying cells of the lesion, and the transition from the epithelial cells of the underlying lesions to squamous cells was evident (Figure 5). In all 8 cases with squamous cell metaplasia, the proliferating squamous cells were confined to the underlying lesions without infiltration into the adjoining parotid parenchyma. Cytologically, the metaplastic squamous cells were usually bland with occasional focal nuclear atypia and mitoses, particularly in the areas near infarction and necrosis (Figure 4). Pseudoducts or luminal structures were seen sometimes in the metaplastic squamous epithelium with intraluminal mucicarmine-positive secretions (Figure 6); however, cytoplasmic mucicarminepositive staining was not observed. Two oncocytic adenomas and 1 pleomorphic adenoma showed extensive central necrosis associated with subepithelial stromal hyalinization (Table 2). One oncocytic adenoma demonstrated extensive subepithelial hyalinization and cystic degeneration without coagulative necrosis (Figure 7). Again, surrounding these changes was metaplastic squamous proliferation, which coalesced into the epithelium of the underlying lesions at its edge. Even in the necrotic areas, ghost outlines of the underlying cells of the lesion were evident (Figure 4). One oncocytic adenoma showed exuberant fibroblastic proliferation with multinucleated giant cells simulating sarcoma (Figure 8). Other histologic alterations included pseudocapsular invasion, linear needle tract with associated fibrosis and hemorrhage, chronic inflammation and hemosiderin-laden macrophages, microcystic formation, cholesterol clefts, and pseudoxanthomatous reaction (Table 2). COMMENT Fine-needle aspiration is a useful diagnostic and screening tool to aid in preoperative management and to avoid unnecessary surgical procedures in patients with palpable superficial and deep-seated lesions in a variety of tissues. Although it is a relatively atraumatic procedure, various histologic alterations have been observed in various tissues. The reported incidence ranges from 1.4% to 85%. 2,3 In the current study, approximately 16% of the in-house cases showed histologic alterations associated with preoperative FNA biopsy. Such a wide variation of reported incidence is probably related to the nature of the underlying lesions, the size of the needle used, the number of passes, and the technique employed. Depending on the presence or absence of diagnostic features, Batsakis et al 8 classified the FNA-associated tissue effects into the following 3 categories: micronecrosis and hemorrhage with retention of diagnostic features, macronecrosis (infarction) with deletion of diagnostic features, and macronecrosis or micronecrosis with reactive proliferation of cells of the lesion and stromal cells. Most changes belong to the first category. Occasionally, the changes almost completely obscure the underlying cells of the lesion, making the diagnosis difficult, if not impossible. In our series, the FNA-induced histologic changes did not entirely obliterate the lesions themselves. Even in cases with extensive FNA artifact, small foci or islands of the 88 Arch Pathol Lab Med Vol 124, January 2000 Alterations Following FNA of Benign Parotid Lesions Li et al

Figure 1. Case 1. A well-circumscribed pleomorphic adenoma with a thick fibrous capsule and extensive central necrosis (hematoxylin-eosin, original magnification 2.5). Figure 2. Case 2. with metaplastic squamous epithelium arranged in cordlike or arcadelike pattern (hematoxylin-eosin, original magnification 100). Figure 3. Case 1. Keratin pearl formation in a nest of metaplastic squamous cells (hematoxylin-eosin, original magnification 100). Figure 4. Case 2. Necrosis surrounded by the metaplastic squamous epithelium with mild cytological atypia in an oncocytic adenoma (hematoxylineosin, original magnification 100). underlying cells of the lesion could be identified at the periphery. In the pleomorphic adenoma, lobules of chondromyxoid stroma were admixed with benign epithelial tubules, nests, and cords. In the oncocytic adenoma, the periphery of the tumor was occupied by eosinophilic cells. The most worrisome histologic change in our study was extensive squamous metaplasia, which can be confused with squamous cell or mucoepidermoid carcinoma. Features that are most helpful in differentiating squamous metaplasia from squamous cell carcinoma are (1) circumscription or roundness of the lesion under low-power view, sometimes with an intact fibrous capsule; (2) central location of the changes within the lesion; (3) association with granulation tissue, chronic inflammation, fibrosis, or sclerosing needle tract; (4) transition from the underlying cells of the lesion to squamous cells; (5) lack of infiltration into the surrounding parotid glands; and (6) bland-appearing nuclear morphology of the metaplastic squamous cells. The mechanism for the squamous metaplasia is unclear. It may represent a regenerative and reparative process after trauma to epithelium and recovery by simplified squamous-type epithelium rather than complex glandular or oncocytic cells, similar to the processes seen in necrotizing sialometaplasia of the minor salivary glands of the palate after trauma 9 or posttraumatic lobular squamous metaplasia of breast. 10 The finding of pseudoducts or luminal structures with Arch Pathol Lab Med Vol 124, January 2000 Alterations Following FNA of Benign Parotid Lesions Li et al 89

Figure 5. Case 4. Transition from oncocytic adenoma to metaplastic squamous epithelium (hematoxylin-eosin, original magnification 100). Figure 6. Case 1. Pseudoducts or luminal structures in the metaplastic squamous epithelium with mucicarmine-positive secretions within the lumens (mucicarmine, original magnification 200). Figure 7. Case 3. with extensive subepithelial stromal hyalinization, fibrosis, and squamous metaplasia (hematoxylin-eosin, original magnification 200). Figure 8. Extensive fibroblastic reaction with multinucleated giant cells in an oncocytic adenoma (hematoxylin-eosin, original magnification 100). mucicarmine-positive secretions within the metaplastic squamous epithelium or extensive subepithelial stromal hyalinization also raises the possibility of a low-grade mucoepidermoid carcinoma. Besides the features already noted, the absence of cytoplasmic mucicarmine-positive inclusions and keratin pearl formation further distinguish the metaplastic squamous cells from a low-grade mucoepidermoid carcinoma. The absence of cysts with mucin also favors the diagnosis of metaplastic squamous epithelium. Extensive necrosis and infarction have been reported in pleomorphic adenoma 5,7 and Warthin tumor. 6 In our study, these changes were observed in 2 oncocytic adenomas and 1 pleomorphic adenoma. The presence of extensive necrosis should alert histopathologists to evaluate the specimens more carefully, especially when it is associated with proliferation of atypical squamous or fibroblastic cells. All the histologic changes described here occur spontaneously. 11 13 In all of our cases, however, the changes seen in the surgical resection specimens were not present in the aspiration material, indicating that the alterations were most likely due to the traumatic injury of needling rather than spontaneous change of the lesions themselves. It is not our intention to discourage the use of FNA in patients with palpable salivary gland lesions because of its subsequent effect on tissue histology. These alterations are infrequent. In the majority of cases, the changes are focal and the underlying cells of the lesion are readily identifiable. Only on rare occasions are the changes so extensive that they could be confused with a malignant dis- 90 Arch Pathol Lab Med Vol 124, January 2000 Alterations Following FNA of Benign Parotid Lesions Li et al

ease. Therefore, it is our purpose to emphasize the importance of recognizing the histologic changes induced by FNA needling and of obtaining the clinical history of a preoperative FNA procedure to avoid potential misdiagnosis. References 1. LiVolsi VA, Merino MJ. Worrisome histologic alterations following fine-needle aspiration of the thyroid (WHAFFT). Pathol Ann. 1994;2:99 120. 2. Ersoz C, Soylu L, Erkocak EU, et al. Histologic alterations in the thyroid gland after fine-needle aspiration. Diagn Cytopathol. 1997;16:230 232. 3. Lee KC, Chan JKC, Ho LC. Histologic changes in the breast after fine-needle aspiration. Am J Surg Pathol. 1994;18:1039 1047. 4. Tabbara SO, Frierson HF Jr, Fechner RE. Diagnostic problems in tissue previously sampled by fine-needle aspiration. Am J Clin Pathol. 1991;96:79 80. 5. Pinto RGW, Couto F, Mandreker S. Infarction after fine needle aspiration: a report of four cases. Acta Cytol. 1996;40:739 741. 6. Kern SB. Necrosis of a Warthin s tumor following fine needle aspiration. Acta Cytol. 1988;32:207 208. 7. Gottschalk-Sabag S, Glick T. Necrosis of parotid pleomorphic adenoma following fine needle aspiration: a case report. Acta Cytol. 1995;39:252 254. 8. Batsakis JG, Sneige N, El-Naggar AK. Fine-needle aspiration of salivary glands: its utility and tissue effects. Ann Otol Rhinol Laryngol. 1992;101:185 188. 9. Abrams AM, Melrose RJ, Howell FV. Necrotizing sialometaplasia: a disease simulating malignancy. Cancer. 1973;32:130 135. 10. Hurt MA, Diaz-Arias AA, Rosenholtz MJ, et al. Posttraumatic lobular squamous metaplasia of breast: an unusual pseudocarcinomatous metaplasia resembling squamous (necrotizing) sialometaplasia of the salivary gland. Mod Pathol. 1988;1:385 390. 11. Layfield LJ, Reznicek M, Lowe M, et al. Spontaneous infarction of a parotid gland pleomorphic adenoma: report of a case with cytologic and radiographic overlap with a primary salivary gland malignancy. Acta Cytol. 1992;36:381 386. 12. Taxy JB. Necrotizing squamous/mucinous metaplasia in oncocytic salivary gland tumors: a potential diagnostic problem. Am J Clin Pathol. 1992;97:40 45. 13. Lam KY, Ng IOL, Chan GSW. Palatal pleomorphic adenoma with florid squamous metaplasia: a potential diagnostic pitfall. J Oral Pathol Med. 1998;27: 407 410. Arch Pathol Lab Med Vol 124, January 2000 Alterations Following FNA of Benign Parotid Lesions Li et al 91