Breast - nonmalignant
Benign tumors / changes
Spindle cell lipoma / pleomorphic lipoma

Author: Cansu Karakas, M.D. (see Authors page)

Revised: 29 December 2015, last major update December 2015

Copyright: (c) 2002-2015,, Inc.

PubMed Search: Spindle cell lipoma [title] breast
Cite this page: Spindle cell lipoma / pleomorphic lipoma. website. Accessed April 25th, 2017.
Definition / General
  • A rare variant of breast lipoma characterized by a mixture of mature adipocytes, collagen forming spindle cells and varying degrees of myxoid change
  • The first report citing breast as a possible location of benign spindle cell tumor was by Toker et al in 1981 (Cancer 1981;48:1615)
  • Usually age > 40 years; no gender preference
  • Although pleomorphic lipoma was initially considered a separate entity, it is now accepted that both tumors are part of a spectrum of neoplasms characterized by similar clinical, morphologic and genetic features (J Cancer Res Clin Oncol 1994;120:707)
Radiology Description
  • Usually appears on mammogram as a well circumscribed mass
  • On ultrasound, usually a homogeneously hyperechoic solid mass or nodule
Case Reports
  • Benign tumors are managed by routine follow up
  • Malignant or potentially malignant tumors should be completely excised
Gross Description
  • Usually 3 to 5 cm, but can be up to 14 cm
  • Most tumors present as a single, well demarcated, firm, unencapsulated mass
  • Cut surface is pale, white to gray with a variably lipomatous and myxoid component
  • Calcification, hemorrhage and necrosis are not present
Gross Images
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White fibrous tumor

Micro Description
  • Spindle cell lipoma typically contains three components: thin, uniform spindle cells arranged in short, parallel bundles, mature adipocytes and ropy birefringent collagen
  • Myxoid background appears as a thin, amorphous and semitransparent substance
  • Very low rate of mitosis, no necrosis
  • Pleomorphic lipomas have prominent floret cells
Micro Images

Images hosted on PathOut server:

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Courtesy of Dr. Mark R. Wick

Images hosted on Other servers:

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Spindle cells associated with collagen

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Cytology, H&E, CD34

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Spindle cells are CD34+

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Spindle cells are desmin-

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Spindle cells are SMA-

Cytology Description
  • Benign spindle cell tumor: presence of spindle cells without ductal epithelial cells
  • Pleomorphic lipoma: Clusters of multinucleated floret-like giant cells with hyperchromatic nuclei; also round cells and few spindle shaped cells (Acta Cytol 2000;44:255)
Positive Stains
Differential Diagnosis