Fine-Needle Aspiration of Epithelial-Myoepithelial Carcinoma of the Parotid Gland With Prominent Adenoid Cystic Carcinoma-Like Cribriform Features: Avoiding a Diagnostic Pitfall.

OBJECTIVES: Epithelial-myoepithelial carcinoma (EMC) is a rare salivary gland malignancy associated with an overall good prognosis. Fine-needle aspiration (FNA) typically shows a dual population of myoepithelial and ductal cells. Rarely, acellular matrix globules are present, raising a differential diagnosis of adenoid cystic carcinoma (AdCC), a more aggressive salivary gland malignancy associated with a poor long-term prognosis. We report an FNA case of EMC containing a predominant pattern of AdCC-like spherical globules. METHODS: We compare features of an unusual case of EMC with those of cribriform AdCC to arrive at morphologic clues to the correct diagnosis. RESULTS: Distinguishing features of EMC on FNA include (1) a prominent population of myoepithelial cells vs the predominance of basaloid cells in AdCC and (2) cohesive matrix globules with a peripheral rim of pale-staining basement membrane material compared with the dyscohesive matrix globules of AdCC. Immunochemical markers (S100, CD117, and MyB) are also useful. CONCLUSIONS: Although EMC and AdCC can both contain spherical matrix globules, close evaluation of the cytomorphology of the globules and their relationship to surrounding cells provides a clue to distinguish the two neoplasms.

ThinPrep for cytologic evaluation of follicular thyroid lesions: correlation with histologic findings.

Fine needle aspiration (FNA) is often the first step in management of a thyroid nodule. Although papillary carcinomas have distinctive features on conventional smears as well as ThinPrep preparations, cytopathologists rely on the architectural arrangement of cells to classify follicular lesions. The accuracy of ThinPrep in this regard has not been determined. We reviewed all thyroidectomy specimens from a 22-mo period that showed a follicular lesion and had one or more preoperative FNA. The architecture of the lesions on histology was classified as predominantly (>70%) macrofollicular (MA), predominantly microfollicular (MI), mixed (MX), or cystic (C). The presence of colloid, Hürthle cell features, cystic change, Hashimoto's thyroiditis, and nonspecific lymphocytic thyroiditis were also recorded. All FNA specimens were processed with the ThinPrep(R) method and were categorized as nondiagnostic, benign (MA or MX), indeterminate (due to suboptimal cellularity), or suspicious (consistent with a microfollicular or Hürthle cell neoplasm) based on cellularity, architectural arrangement of the follicular cells, and the presence or absence of colloid on FNA. Those cytologic specimens in the indeterminate category were subcategorized as suggestive of an MA, MX, or MI lesion if possible. Histocytologic findings were correlated using Fisher's exact test. A total of 95 patients with 115 FNAs were included in the study (mean age: 48 yr; 75 females and 20 males). Seven of the FNAs were nondiagnostic, 23 benign, 69 indeterminate (5, 8, and 30 favor MA, MX, and MI, respectively, 6 cyst contents and 20 not subclassifiable) and 16 suspicious. The cytohistologic correlation for architecture was significant (P = 0.003). The cytohistologic correlation of cystic change, Hürthle cell change, and the presence of colloid (large fragments of colloid and "tissue-paper-like material" on cytology vs. abundant colloid on histology) was highly significant (P < 0.001, < 0.001, and < 0.03, respectively). In conclusion, thyroid FNA with ThinPrep is useful in predicting the architectural pattern of follicular lesions. It is also reliable in predicting cystic change, Hürthle cell change, and the presence of colloid. Watery colloid is probably present as "tissue-paper-like material" in thyroid FNA ThinPrep preparations.