Fine-Needle Aspiration Cytology of Low-Grade Cribriform Cystadenocarcinoma with Many Psammoma Bodies of the Salivary Gland
A 90-year-old man presented with a palpable mass on his left postauricular region that had been present for three years. The mass was hard, fixed, and recently increased in size. These symptoms were not accompanied by pain, tenderness, local hotness, or recent weight loss. The patient was healthy for his age and had an unremarkable medical history.\nMagnetic resonance imaging revealed a well-enhanced 5 cm solid mass including a cystic component in the left parotid gland. The margin of the mass was partly ill-defined. Neither regional nor distant metastasis was found on positron emission tomography-computed tomography scan. The initial diagnosis from clinical and radiologic evidence was a metastatic lymph node or a malignant tumor of the parotid gland. FNA of the tumor was performed.\nPapanicolaou-stained smears revealed that tumor cells were arranged both in tight clusters and individually dispersed (). The tumor cells had round or oval nuclei with mild atypia. Most of the tumor cells had fine chromatin without prominent nucleoli, but some had inconspicuous small nucleoli (). The cytoplasm was scant in most of the tumor cells, and numerous naked cells were identified (). Some tumor cells had a polygonal shape with dense opaque cytoplasm, which suggested squamoid differentiation even though no obvious keratin material was noted (), and a few had cytoplasmic vacuoles of various sizes (). Cytoplasmic granules were not found. Inflammatory cells, including lymphocytes, neutrophils, and some macrophages were scattered across the background, and characteristically, numerous psammoma bodies were identified throughout the smears. Most psammoma bodies were present in the background and not connected to the tumor cells, but some of them were surrounded by tumor cells (, inset). Necrosis, mucin, and myxoid stromal components were not found in the background, and only one mitotic figure was noted. In view of these cytologic findings, we considered the possibility of either a malignant tumor of the parotid gland or a metastatic tumor of some other organs, most likely the thyroid gland. The possibility of a metastatic thyroid carcinoma could not be excluded because of the presence of many psammoma bodies, which are unusual findings in FNA of salivary glands. No other findings suggesting a specific type of thyroid carcinoma were identified, and no intra-thyroidal lesion was found in radiological examination. Therefore, we diagnosed a low-grade malignancy of the parotid gland and recommended complete excision of the mass.\nWe surgically removed the parotid gland, which measured 8.5 cm×6 cm×5 cm. On a cut section, a tan to gray solid tumor with a cystic area measuring 5.3 cm×4.5 cm×4 cm was seen. It was relatively well demarcated from the surrounding parotid gland but was nonencapsulated. In the cystic area of the tumor, an intracystic papillary-growing pattern was noted (). Microscopically, the tumor was composed of multilocular cystic lumens in the periphery and solid or papillary proliferation of tumor cells with fibrous stroma in the cystic area (). The cystic lumens were lined by two or more bland tumor cells. In the intracystic solid area, the tumor cells were arranged in papillary, cribriform, and solid patterns (). The cystic lumens were filled with pink secretory materials, including some macrophages. The tumor cells had round to oval nuclei with inconspicuous nuclear atypia and eosinophilic or clear cytoplasm. Mitotic figures were very rare (<1/10 high power fields), and necrosis was absent. Cellular pleomorphisms and prominent nucleoli were not observed, but some small nucleoli were present. Neither perineural nor vascular invasion were present, but focal stromal invasion of the tumor cells into the fibrotic stroma was noted. Numerous psammoma bodies were observed in fibrotic stroma and between the tumor cells (). All these microscopic findings in the surgical specimen were similar to the cytologic findings from preoperative FNA. Immunohistochemically, most tumor cells were positive for S-100 protein (). Smooth muscle actin (SMA) () and p63 () were positive only in the periphery of the cystic lumens and the rims of papillary, cribriform, and solid tumor cell nests, which suggests intracystic or intraductal growth. The Ki-67 proliferation index was less than 5%. Thyroid transcription factor-1 (TTF-1) and thyroglobulin were negative.