Rare histologic presentation of pleomorphic adenoma: A diagnostic dilemma

Abstract

Pleomorphic adenoma is the most common benign salivary gland tumor deriving its name from varied morphological patterns in histopathology. The presence of chondromyxoid stroma in histopathology is characteristic of pleomorphic adenoma. Cellular variants without characteristic chondromyxoid stroma are rare and often pose a diagnostic challenge. We report a case of pleomorphic adenoma involving minor salivary glands of the palate presenting with a predominantly cellular histopathology. Immunohistochemical workup was pivotal in the diagnosis of this challenging case.

Keywords: Minor salivary glands; moderately cellular; palate; pleomorphic adenoma; salivary gland tumor.

Figure 1

Intraoral photograph showing a solitary, diffuse and ovoid swelling in the right posterior hard palate

Figure 2

Orthopantamograph did not reveal any hard tissue involvement

Figure 3

Axial computed tomography revealing a soft-tissue density in the right lateral aspect of the hard palate

Figure 4

Excisional biopsy of the lesion under local anesthesia

Figure 5

Histopathological images of hematoxylin and eosin stained sections. (a) Histopathological image showing moderately cellular lesion with sheets and strands of polyhedral squamous epithelial cells exhibiting duct-like structures containing eosinophilic coagulum interspersed with hyalinized areas (H&E stain, ×40). (b) Histopathological image showing duct-like structures, hyalinized areas with spindle-shaped, angular and stellate myoepithelial cells (H&E stain, ×100). (c) Histopathological image showing “cribriform-like” pattern containing multiple cyst-likespaces (H&E stain, × 200). (d) Histopathological image showing plasmacytoid myoepithelial cells (→) with eosinophilic cytoplasm and eccentrically placed nuclei (H&E stain, ×400)

Figure 6

Immunohistochemical evaluation of tissue sections. (a) A population of spindle-shaped, angular and stellate myoepithelial cells exhibiting intense, cytoplasmic expression of smooth muscleactin (×400). (b) Tumor cells exhibited diffuse positivity for Glial Fibrillary Acidic Protein (×400). (c) Ki-67 labeling index was 4% (×400)