Fat Free Pleomorphic Lipoma of Oral Cavity: A Rare Entity

Abstract

Pleomorphic lipoma is a rare, benign, soft tissue neoplasm that characteristically occurs as a subcutaneous mass in the posterior neck or upper back and rarely in the tonsillar fossa and oral cavity. Histologically, pleomorphic lipoma contains varying amounts of mature fat, areas of spindle and pleomorphic cells, floret giant cells and thick rope - like collagen in a myxoid stroma. Pleomorphic lipoma with scanty fatty elements is called the fat free variant of pleomorphic lipoma. The combination of meagre amount of fat and presence of pleomorphic elements gives a pseudosarcomatous picture under the microscope leading to misdiagnosis and over treatment. Here, we report a case of fat free pleomorphic lipoma, first of its kind in the oral cavity and discuss the diagnostic features and differential diagnosis.

Keywords: Floret giant cells; Ropey collagen; Soft tissue neoplasm.

[Table/Fig-1]:

a) Diffuse swelling 2 cm lateral to the right corner of the mouth. b) A well-defined T2/STIR hyperintense, T1 isointense radiopaque lesion measuring 18.7x18.4x14.7 mm in the subcutaneous plane of right cheek (red arrow).

[Table/Fig-2]:

Intraoperative photograph showing in toto removal of the lesion.

[Table/Fig-3]:

Specimen photograph showing translucent jelly like colour of the specimen.

[Table/Fig-4]:

Low power view of the lesion shows a mixture of pleomorphic spindled cells and thick ropey collgen (H&E; 10X).

[Table/Fig-5]:

Negligible amount of fat like areas (green arrow) seen amidst pleomorphic spindled cells. Rope like collagen seen here (red arrow) (H&E;10X).

[Table/Fig-6a,b]:

High power view of the pleomorphic spindle cells with hyperchromatic bizarre nucleus (H&E; 20X). (Images left to right)

[Table/Fig-7]:

Coarse rope like collagen randomly distributed in diffuse myxoid stroma (H&E; 20X).

[Table/Fig-8a,b]:

Floret like multinucleated giant cell with radially arranged hyperchromatic nuclei and central eosinophilic cytoplasm, (red arrow) (H&E; 20X).

[Table/Fig-9]:

a) Positive immunoreactivity with CD34 (IHC, 20X); negative immunostaining with; b) CD68 (IHC, 20X); c) Ki-67 (IHC, 20X); d) S-100 (IHC, 20X); e) SMA (IHC, 10X).