J Pathol Transl Med.  2018 Nov;52(6):411-415. 10.4132/jptm.2018.07.15.

Squamous Metaplasia in Pleomorphic Adenoma: A Diagnostic and Prognostic Enigma

• Sharma S
• Mehendiratta M
• Chaudhary
• Gupta V
• Kohli M
• Arora A

• KMID: 2427524
• DOI: http://doi.org/10.4132/jptm.2018.07.15

Abstract

Pleomorphic adenoma (PA) is the most common benign salivary gland tumor. Histologically, squamous metaplasia has been reported in PA, but has rarely been documented as being extensive enough to cause significant misdiagnosis. Here, we present an unusual case of PA in a 50-year-old female patient presenting with swelling on the postero-lateral aspect of the palate for a week. Histopathologically, the tumor exhibited the features of conventional PA with extensive squamous metaplasia and giant keratotic lamellae in cyst-like areas. Such exuberant squamous metaplasia and keratin can be a diagnostic and prognostic pitfall and lead to overtreatment of the patient.

Keyword

Squamous metaplasia; Pleomorphic adenoma; Pathology

MeSH Terms

Adenoma, Pleomorphic*
Diagnostic Errors
Female
Humans
Medical Overuse
Metaplasia*
Middle Aged
Palate
Pathology
Salivary Glands

Figure

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  Fig. 1. (A) Swelling associated with central ulceration covered by a fibrino-purulent membrane and surrounded by palatal erythema can be seen on the right distal side of the hard palate, laterally. (B) A well-encapsulated tumor removed in toto from the palate.

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  Fig. 2. (A) Reconstructed panoramic image shows the polyp at the level of the mid right maxillary sinus. (B) Axial section shows inflamed sinus lining involving the right maxillary sinus. (C) Cone beam computed tomography (CBCT) mid-coronal section of the right maxillary third molar (18) showing the soft tissue shadow palatally. (D) Two-three dimensional CBCT image showing the antero-posterior extent of the swelling.

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  Fig. 3. (A) The periphery of the tumor with classical features of pleomorphic adenoma having abundant ducts dispersed in a myxoid and hyalinized background with multiple keratin-filled cystic areas. (B) Multitude of features, including variably shaped epithelial cells, ducts, and squames. Keratin-filled cysts dispersed in the myxoid stroma. (C) Abundant myoepithelial cells around the ducts giving the appearance of a swarm of bees. (D) Massive epithelial lined cysts with keratotic lamellae and the lining budding into the stroma.

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