Fine needle aspiration cytology of polymorphous adenocarcinoma of the salivary glands: A report of 11 patients and review of the literature

Abstract

Background: Polymorphous adenocarcinoma (PAC) is a rare malignant tumor of the minor salivary glands. It has an infiltrative growth, variable architectural patterns, neurotropism and cellular monomorphism. Approximately 75% of the cases show a specific mutation in the protein kinase D1 (PRKD1) gene. Reflecting the rarity of the tumor and intraoral location, the cytologic experience is limited with few reported series. In this study we analyze our cytologic experience to determine if a preoperative diagnosis is possible. Methods: A retrospective study of 11 patients with PAC in which a cytologic study was available. A review of the literature was also performed. Results: Our study shows that PAC has relatively constant cytological features. The analysis of the cytological literature although it shows some heterogeneity, also reveals repetitive cytological findings. Smears are cellular with irregular groups some showing pseudopapillary branching morphology. Monolayered clusters and small acinar structures are also present. Most cases have small metachromatic globules embedded within the groups determining a cylindromatous pattern. Tumoral cells are small and uniform with scarce to moderate cytoplasm. Nuclei are round and oval with occasional grooves and small nucleoli. Conclusion: PAC has characteristic cytological features that together with its location in minor salivary gland must make us consider it preoperatively. It may resemble basal cell adenoma and epithelial-rich pleomorphic adenoma so we should be cautious in the final diagnosis. Whenever possible, the characteristic cytomorphology of PCA should make us evaluate the mutational status of PRKD1 gene since it may permit a more accurate diagnosis.

Classic polymorphous adenocarcinoma: Fine needle aspiration cytopathology of eight cases

“…The cytomorphology of aspirates from our series largely mirrors that described from prior reports of the relatively sparse literature regarding this tumor 7‐19 . Cell uniformity is constant in nearly all cases of PAC as is the presence of tightly aggregated cell clusters, a clean smear background, and architectural heterogeneity among cell collections.…”

“…These include rounded and branching cell aggregates, multilayered folding of cell groups, papillary‐like features, and cells in flat plates as illustrated in Figure 1A‐D. Although intranuclear inclusions and/or tyrosine‐rich crystals have been cited by some authors, 8,9,11,13 these were not convincingly present in our cases, and are not specific for PAC. Nor was mucinous, apocrine, clear cell, or oncocytic change seen, which has been described as part of the diverse histopathology seen in PAC 5 .…”

“…PAC is an SG neoplasm where FNA biopsy has had limited success in accurate diagnostic recognition. In the literature review by Jiménez-Heffernan et al there were 35 cases (including 12 from their own series) where a specific FNA diagnosis was listed, 9 whereas three articles from that review failed to list a specific FNA diagnosis. 7,11,17 When one combines the diagnoses listed in that revew 9 and the diagnoses from two other PAC FNA cases, 19,22 an accurate FNA interpretation of PAC occurs in less than half (49%) of the cases.…”

“…In the literature review by Jiménez-Heffernan et al there were 35 cases (including 12 from their own series) where a specific FNA diagnosis was listed, 9 whereas three articles from that review failed to list a specific FNA diagnosis. 7,11,17 When one combines the diagnoses listed in that revew 9 and the diagnoses from two other PAC FNA cases, 19,22 an accurate FNA interpretation of PAC occurs in less than half (49%) of the cases. This includes both primary and metastatic FNA PAC cases, as well as two cases where the diagnosis was low-grade adenocarcinoma, rather than PAC specifically.…”

Cytomorphologic features of intraductal salivary gland carcinoma: A multi‐institutional study of 13 FNA cases with histologic, molecular, and clinical correlations

“…18,19 Polymorphous adenocarcinoma may have a similar immunoprofile overlapping with IDC; however, this is most often in the minor salivary glands, whereas IDC is most often localized to the parotid gland. 4,20 In addition, polymorphous adenocarcinoma often displays an unusual and distinct p63+/p40-immunoprofile. In contrast to LG IDC, 67% of HG IDCs express androgen receptor and Her2/Neu.…”