Page 552 - Textbook of Pathology, 6th Edition

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Figure 19.15 Warthin’s tumour, showing eosinophilic epithelium forming glandular and papillary, cystic pattern with intervening stroma of
lymphoid tissue.

cells with glandular eosinophilic cytoplasm (oncocytes). It It is the most common example of radiation-induced malig-
is also called as mitochondrioma because of cytoplasmic nant tumour, especially therapeutic radiation.
granularity due to mitochondria.
MORPHOLOGIC FEATURES. Grossly, the tumour is
OTHER TYPES OF MONOMORPHIC ADENOMAS. usually circumscribed but not encapsulated. It varies in
There are some uncommon forms of monomorphic size from 1 to 4 cm.
adenomas: Microscopically, the tumour is classified into low, inter-
i) Myoepithelioma is an adenoma composed exclusively of mediate and high grade depending upon the degree of
myoepithelial cells which may be arranged in tubular, differentiation and tumour invasiveness. The tumour is
SECTION III
alveolar or trabecular pattern. composed of combination of 4 types of cells: mucin-
ii) Basal cell adenoma is characterised by the type and producing, squamous, intermediate and clear cells. Well-
arrangement of cells resembling basal cell carcinoma of the differentiated tumours have predominance of mucinous
skin. cells, while poorly differentiated have more solid and
iii) Clear cell adenoma has spindle-shaped or polyhedral cells infiltrative pattern (Fig. 19.16).
with clear cytoplasm.
MISCELLANEOUS BENIGN TUMOURS

A number of mesenchymal tumours can rarely occur in
salivary glands. These include: fibroma, lipoma, neurilem-
Systemic Pathology
momas, neurofibroma, haemangioma and lymphangioma.

B. MALIGNANT SALIVARY GLAND TUMOURS
Mucoepidermoid Carcinoma

The status of ‘mucoepidermoid tumour’ as an intermediate
grade tumour in the previous classification has undergone
upgradation to mucoepidermoid carcinoma now having the
following peculiar features:
It is the most common malignant salivary gland tumour
(both in the major and minor glands).
The parotid gland amongst the major salivary glands and
the minor salivary glands in the palate are the most common
sites.
Common age group affected is 30-60 years but it is also
the most common malignant salivary gland tumour affecting Figure 19.16 Mucoepidermoid carcinoma. The tumour shows
combination of mucinous, squamous and intermediate cells and having
children and adolescents. infiltrative border.