Abstract
Pleomorphic lipoma is a relatively uncommon entity, and is considered as a variant of spindle cell lipoma. Histologically, spindle cell lipoma/pleomorphic lipoma consists of varying quantity of mature fat, bland spindle cells and ropey collagen. In addition, pleomorphic lipoma is characterized by multinucleate giant cells, which possess the “floret-like” nuclei and marked pleomorphism. So, in contrast to spindle cell lipoma, pleomorphic lipoma is more easily misdiagnosed as a malignant tumor. Herein, we report a peculiar case of pleomorphic lipoma occurring in axilla with entirely devoid of mature fat in a 71-year-old male. The histopathological findings demonstrated the tumor was made up of bland spindle cells admixed with scattered “floret-like” cells and irregular ropey collagen in an extensive myxoid stroma. Immunostaining showed that the tumor was positive for the Vimentin, Bcl-2 and CD34, and was negative for S-100, desmin, CD68, and α–SMA. Although no fat component was found in the whole section, the tumor was still diagnosed as a pelomprphic lipoma. To our knowledge, this is the third reported case of pelomprphic lipoma which entirely lacked lipomatous component. Because of the existence of atypical multinucleate giant cells and lack of mature fat, this tumor may be easily misdiagnosed nonlipomatous lesions, such as myxoid fibrosarcoma, giant cell fibroblastoma.So, it is necessary to pay careful attention to the histological spectrum of pleomorphic lipoma, including the tumor with devoid of fat, and it should be kept in mind that pelomprphic lipoma still can be diagnosed even if lacking lipomatous component.Virtual slidesThe virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1967123180611361
Highlights
Pleomorphic lipoma was first described by Shmookler and Enzinger in 1981 [1], 6 years later than the first description of spindle cell lipoma by Enzinger and Harvey [2]
Tissue blocks were cut into 4-μm slides, deparaffinized in xylene, rehydrated with graded alcohols, and immunostained with the following antibodies: Vimentin, CD34, S-100, desmin, α–smooth muscle actin (α–SMA), Bcl-2, CD68 and Ki-67
The tumor was made up of hypocelluar bland spindle cells admixed with scattered multinucleated cells and irregular ropey collagen in a diffuse myxoid stroma
Summary
Pleomorphic lipoma was first described by Shmookler and Enzinger in 1981 [1], 6 years later than the first description of spindle cell lipoma by Enzinger and Harvey [2]. Pleomorphic lipoma occurs predominantly in the subcutaneous tissue of the posterior neck, shoulder, and back [1]. Less frequently, it can occur in unusual locations including palm [9], tonsillar fossa [10], orbit [11], tongue [12], vulva [13] and oral cavity [14]. Some tumors may predominantly consist of adipose tissue with scattered spindle cells or “floret-like” cells, others may predominantly consist of spindle cells and “floret-like” cells with a little adipose tissue Very rarely, it may entirely lack mature adipocytes which can pose a great challenge, and be misdiagnosed
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