G. Seifert et al., Lipomatous pleomorphic adenoma of the parotid gland. Classification of lipomatous tissue in salivary glands, PATH RES PR, 195(4), 1999, pp. 247-252
Lipomatous pleomorphic adenoma is an unusual subtype with a lipomatous stro
mal component of more than 90% of the tumour tissue. This special type of p
leomorphic adenoma must be distinguished from other types of lipomatous tum
ours or non-tumourous lipomatosis of the salivary glands. Until now only tw
o cases of lipomatous pleomorphic adenoma have been reported in the literat
ure. We report of a 36-year old woman who developed a well circumscribed no
dule measuring 3,5 x 2,5 x 2 cm in the right parotid gland. The cut surface
was grey-yellowish. Histologically, more than 90% of the tumour tissue was
fatty tissue with univacuolar adipocytes. The pleomorphic epithelial eleme
nts were duct-like cells forming small lumina and spindle-shaped myoepithel
ial cell with surrounding mucoid stroma. Components of pleomorphic adenoma
were intermingled with mature adipose tissue which was more concentrated in
the central portion of the adenoma. Some compressed epithelial cords in th
e adipose tissue formed a septa-like pattern. The differential diagnosis to
other lipomatous tumours (lipoadenoma, lipoma) and to nontumourous interst
itial lipomatosis as well as the possible pathogenesis as metaplastic chang
e or epithelial-mesenchymal transdifferentiation are discussed.