Pleomorphic lipoma lacking mature fat component in extensive myxoid stroma: a great diagnostic challenge

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

Pleomorphic lipoma of the neck in an infant: A rare clinical entity

“…[ 6 ] However, this tumor has always been seen in older men ranging with a median of over 55 years. [ 3 ] This is the first case report in the pediatric age group.…”

“…[ 10 ] In addition, multinucleated giant cells are scattered amid the spindle cells, and their nuclei are radically arranged in a “floret-like” pattern. [ 2 3 ] The spectrum of the histology shows a wide variation and varies from tumor(s) that resembles ordinary lipoma with few spindle cells to tumor that mainly consists of spindle cells with just a few fat cells. Cytologically, spindle cells have single elongated hyperchromatic nuclei and inconspicuous nucleoli, whereas multinucleated giant cells have irregular, hyperchromatic, and significantly atypical nuclei.…”

“…[ 2 ] Pleomorphic lipomas are rare variants of spindle cell lipoma occurring in men in the seventh and eight decades. [ 3 ] An extensive literature search shows no reported cases in children. We report the first case of pleomorphic lipoma, in the pediatric population to the best of our knowledge.…”

Pleomorphic lipoma in the anterior mediastinum: A case report

“…Furthermore, PLS tumors are basically free from mucous components. On the contrary, PL presents with almost no mitosis, hemorrhage, or necrosis, which is significantly different from PLS[9].…”

Solitary myofibroma of the sigmoid colon: case report and review of the literature

“…Therefore, pathologists should be aware of the histologic spectrum of the tumors to avoid mistaken diagnosis of malignancy. For example, pleomorphic lipoma can be misdiagnosed as a nonlipomatous tumor such as myxofibrosarcoma if the tumor lacks mature fat component [8]. Similarly, solitary fibrous tumor is one of the tumors which can show a wide range of morphologic features [9].…”