**Diagnostic challenges and pitfalls – Polymorphous Adenocarcinoma (POA).**

The cytological features of POA may resemble PA or ADCC [30]. The matrix of POA may be fibrillar and myxoid resembling a PA or can form hyaline globules similar to ADCC. However, the papillary architecture of cells is found in POA and its presence can distinguish it from PA and ADCC. The cells of ADCC are basaloid with coarse nuclear features rather than fine open nuclear features seen in POA [30].

## **4.2 Cystic tumours**

Cystic tumours of intraoral SGs range from benign tumours such as sclerosing polycystic adenosis, cystadenoma, cystic PA, duct papilloma to malignant tumours such as low-grade MEC and papillary cystic variant of acinic cell carcinoma (AciCC). Evaluation and interpretation of these cystic tumours is particularly challenging as usually the aspirate of these tumours is hypocellular. This may result in false negative diagnosis particularly in a low-grade malignant cystic tumours.

#### **Figure 7.**

*7a: Smear showing monomorphic small round to oval epithelial cells attached to fibrous stromal core in a case of polymorphous adenocarcinoma (Papanicolaou stain x 40), 7b: Corresponding histology showing growth of tumour cells in glandular and acinar pattern (black arrows) surrounded by adjacent fibrous stroma (white arrows) (Haematoxylin & Eosin x 10).*

*Cytopathology of Intraoral Salivary Gland Tumours and Tumour-Like Lesions… DOI: http://dx.doi.org/10.5772/intechopen.98872*
