- Case Report
- Open Access
A case of lipomatous pleomorphic adenoma in the parotid gland: a case report
© Kondo; licensee BioMed Central Ltd. 2009
Received: 30 March 2009
Accepted: 04 June 2009
Published: 04 June 2009
Pleomorphic adenoma is the most common benign neoplasm of the salivary glands. Extensive lipomatous involvement of the tumor is, however, a very rare finding.
Herein, a rare case of lipomatous pleomorphic adenoma arising in the parotid gland of a 14-year-old Japanese woman is presented.
This is the sixth case of lipomatous pleomorphic adenoma in the English literature. Recognition of this rare subtype of pleomorphic adenoma is important for clinical diagnosis and management. On CT scan, it may not be detected possibly due to the extensive fatty component.
Pleomorphic adenoma is the most common benign neoplasm of the salivary glands, with the highest predilection for the parotid gland. The term 'pleomorphic' refers to both histogenesis and histology of the tumor. As the term 'pleomorphic' shows, the tumor is characteristic of the diversity of the histology. Lipomatous component can be included in pleomorphic adenoma. Extensive lipomatous involvement of the tumor is, however, a very rare finding in pleomorphic adenoma, with only five cases in the English literature [1–5]. Herein, I present the pathological findings of lipomatous pleomorphic adenoma.
The term, lipomatous pleomorphic adenoma, was coined by Seifert et al.  in 1999, who defined this tumor as an otherwise typical pleomorphic adenoma with an abundant adipose component of more than 90% of the tumor area. This newly described variant is extremely rare and only five cases exist in the literature [1–5]. And this is the sixth case in the English literature. Additional file 1 summarizes the reported cases. No common symptoms of lipomatous pleomorphic adenoma were found.
Various forms of lipomatous tissue associations within salivary glands have been defined (lipoma, interstitial lipomatosis, lipoadenoma, oncocytic lipoadenoma, sialolipoma, and lipomatous atrophy). Although foci of adipose tissue are sometimes encountered within the stroma of pleomorphic adenoma, extensive replacement by adipose tissue like this case is a very rare finding. Differential diagnosis especially concerning lipoma (pure lipomatous tumor) is essential. The existence of epithelial or myoepithelial component is a diagnostic clue.
The histogenesis of lipomatous pleomorphic adenoma is not clear. Metaplastic transformation of myoepithelial cells to adipocytes and entrapment of fat tissue are two possible mechanisms.
Recognition of this rare form of pleomorphic adenoma is also important for clinical diagnosis and management. On CT scan, it may not be detected possibly due to the extensive fatty component that blends with the normal parotid gland.
In conclusion, a rare case of lipomatous pleomorphic adenoma is presented, which is the sixth case in the English literature. Recognition of this rare subtype of is essential for clinical diagnosis, management, and treatment.
Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
I thank very much Dr. Shojiroh Morinaga at Kitasato Institute Hospital, the consultant of this case. I also thank Hiroko Maeda-Kondo for helpful discussion.
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