Page 551 - Textbook of Pathology, 6th Edition

535

Figure 19.14 Pleomorphic adenoma. The epithelial element is comprised of ducts, acini, tubules, sheets and strands of cuboidal and myoepithelial
cells. These are seen randomly admixed with mesenchymal elements composed of pseudocartilage which is the matrix of myxoid, chondroid and
mucoid material.

solid but occasionally may show small cystic spaces. The adenoma may metastasise to distant sites which too will have
consistency is soft and mucoid. benign appearance as the original tumour. However, actual
Microscopically, the pleomorphic adenoma is charac- malignant transformation can also occur in a pleomorphic
terised by pleomorphic or ‘mixed’ appearance in which adenoma (vide infra). CHAPTER 19
there are epithelial elements present in a matrix of mucoid,
myxoid and chondroid tissue (Fig. 19.14): Monomorphic Adenomas
Epithelial component may form various patterns like These are benign epithelial tumours of salivary glands
ducts, acini, tubules, sheets and strands of cells of ductal without any evidence of mesenchyme-like tissues. Their
or myoepithelial origin. The ductal cells are cuboidal or various forms are as under:
columnar, while the underlying myoepithelial cells may
be polygonal or spindle-shaped resembling smooth WARTHIN’S TUMOUR (PAPILLARY CYSTADENOMA
muscle cells. The material found in the lumina of duct- LYMPHOMATOSUM, ADENOLYMPHOMA). It is a
like structures is PAS-positive epithelial mucin. Focal benign tumour of the parotid gland comprising about 8% of
areas of squamous metaplasia and keratinisation may be all parotid neoplasms, seen more commonly in men from
present. Immunohistochemically, the tumour cells are 4th to 7th decades of life. Rarely, it may arise in the submandi-
immunoreactive for epithelial (cytokeratin, EMA, CEA) bular gland or in minor salivary glands. Histogenesis of the
as well as myoepithelial (actin, vimentin and S-100) tumour has been much debated; most accepted theory is that The Oral Cavity and Salivary Glands
antibodies. the tumour develops from parotid ductal epithelium present
in lymph nodes adjacent to or within parotid gland.
Mesenchymal elements are present as loose
connective tissue, and as myxoid, mucoid and chondroid MORPHOLOGIC FEATURES. Grossly, the tumour is
matrix, which simulates cartilage (pseudocartilage) but is encapsulated, round or oval with smooth surface. The cut
actually connective tissue mucin. the matrix of the tumour surface shows characteristic slit-like or cystic spaces,
has been characterised as a product of myoepithelial cells containing milky fluid and having papillary projections.
as seen by S-100 immunostain positivity. However, true Microscopically, the tumour shows 2 components:
cartilage and even bone may also be observed in a small epithelial parenchyma and lymphoid stroma (Fig. 19.15):
proportion of these tumours. Epithelial parenchyma is composed of glandular and
The epithelial and mesenchymal elements are inter-
mixed and either of the two components may be dominant cystic structures having papillary arrangement and is
lined by characteristic eosinophilic epithelium. Variants
in any tumour.
of epithelial patterns include presence of mucous goblet
cells and sebaceous differentiation.
PROGNOSIS. Pleomorphic adenoma is notorious for Lymphoid stroma is present under the epithelium in
recurrences, sometimes after many years. The main factors the form of prominent lymphoid tissue, often with
responsible for the tendency to recur are incomplete surgical germinal centres.
removal due to proximity to the facial nerve, multiple foci of
tumour, pseudoencapsulation, and implantation in the OXYPHIL ADENOMA (ONCOCYTOMA). It is a benign
surgical field. Although the tumour is entirely benign, under slow-growing tumour of the major salivary glands. The
exceptionally rare circumstances, an ordinary pleomorphic tumour consists of parallel sheets, acini or tubules of large