*4.3.5 Secretory carcinoma (SC)*

Previously called as mammary analogue secretory carcinoma, it is a new subtype of SG carcinoma and is reported to occur in minor salivary gland [43]. It also shows cells with vacuolated to clear cytoplasm.

**Key cytological features –** Aspirates show loosely cohesive epithelial cells arranged in small sheets, papillary fragments, acinar groups or follicular structures and also dispersed singly. The cells show variable cytoplasm ranging from granular to vacuolated and eosinophilic to clear cytoplasm. The cells show minimal or no pleomorphism. Background shows mucinous material.

**Diagnostic challenges and pitfalls –** The vacuolated cells may resemble cells of AciCC but lack intracytoplamic zymogen granules. Also, IHC on cell blocks is positive for markers such as mammaglobin, S-100 and vimentin and negative for DOG1 [41, 43].

### **4.4 Oncocytic tumours**

#### *4.4.1 Oncocytoma*

Oncocytoma is a benign tumours of SG predominantly occurring in parotid. However, these tumours are also known to occur in intraoral minor SGs [44].

**Key cytological features –** The cells are seen in two or three dimensional and multilayered clusters. The cells are round to polygonal with oncocytic morphology consisting of dense granular abundant cytoplasm with a round nucleus and distinct nucleolus (**Figure 10b**). The background is clean without debris, fluid and lymphocytes. The oncocytic cytoplasm of cells containing abundant mitochondria can be highlighted by strong positivity for phosphotungstic acid-haematoxylin (PTAH) stain.

#### **Diagnostic challenges and pitfalls – Oncocytic Tumours**


e.Warthin's Tumour constitutes 5–15% of all salivary gland tumours. Although, it shows cohesive two or three- dimensional clusters of oncocytic cells resembling an oncocytoma but it occurs almost exclusively within the parotid gland [46]. The background is usually cystic with debris, lymphocytes and lympho-histiocytes.
