Spindle Cell and Pleomorphic Lipoma

Amitabh Srivastava, MD

Key Facts

Terminology

Benign adipocytic tumors with variable admixture of spindle cells, mucinous stroma, ropey collagen, and multinucleate giant cells

Clinical Issues

Typically in older men (> 50 years)
Shoulder and posterior neck most common sites
Benign behavior

Macroscopic Features

Well-circumscribed subcutaneous lesions
Yellow-gray white, firm with myxoid areas

Microscopic Pathology

Spindle cells with ropey collagen, mature adipose tissue, and myxoid stroma with mast cells
Spindle cells are diffusely/strongly positive for CD34
Pleomorphic lipoma shows multinucleated tumor giant cells with peripheral nuclei (“floret” cells)
Lipoblasts may be present in some PL
Variants
- Pseudoangiomatoid variant of SCL shows prominent slit-like spaces resembling vascular channels
- Spindle cell proliferation dominates the picture in fat-free and fat-poor variant of SCL

Ancillary Tests

Deletions of 16q and 13q occur in SCL/PL

Top Differential Diagnoses

Dermatofibrosarcoma protuberans (DFSP)
Peripheral nerve sheath tumors
Solitary fibrous tumor (SFT)

Spindle cell and pleomorphic lipomas are well-circumscribed tumors with a pale yellow, homogeneous appearance that lacks the lobular configuration seen in typical lipomas.

Spindle cell lipomas show mature adipocytes admixed with a bland spindle cell proliferation in a dense collagenous stroma.

TERMINOLOGY

Abbreviations

Spindle cell lipoma (SCL)/pleomorphic lipoma (PL)

Definitions

Benign adipocytic tumor with variable admixture of spindle cells, ropey collagen, and multinucleated tumor giant cells

CLINICAL ISSUES

Epidemiology

Age
- Typically in older age group (> 50 years)
Gender
- Predominantly in men; < 10% in women

Site

Shoulder and posterior neck most common sites of involvement
Other sites
- Upper arm
- Face
- Oral cavity
Lower extremity involvement is rare

Presentation

Painless mass
- Dermal or subcutaneous nodule
- Often present for long duration
- Rarely multiple or familial

Treatment

Conservative surgical excision is adequate

Prognosis

Benign behavior
Local recurrence is rare

MACROSCOPIC FEATURES

Gross Appearance

Well-circumscribed tumor
Yellow-gray white appearance
Firm consistency
Some cases may show myxoid appearance

MICROSCOPIC PATHOLOGY

Histologic Features

Spindle cell lipoma is composed of variable admixture of 3 components
- Mature adipocytes
- Bland spindle cell proliferation
- Myxoid stroma with ropey collagen and mast cells
Pleomorphic lipoma is part of same spectrum
- In addition to above features, also shows multinucleated tumor giant cells with peripherally arranged nuclei (“floret cells”)
- Lipoblasts may be present in pleomorphic lipoma