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Case 374 - Discussion

Uploaded: 2009-10-30, Updated: 2009-11-03

 

Spindle Cell/Pleomorphic Lipoma

CLINICAL FEATURES

  • Mostly in men 45-60 years of age, in the subcutaneous tissue of the posterior neck, shoulder and back.

  • Typically slowly growing, solitary, painless, firm nodule.

GROSS FINDINGS

  • Well circumscribed, soft yellow, with focal gray-white gelatinous areas, of increased cellularity.
  • Some tumors show extensive myxoid changes or lipomatous changes.

MICROSCOPIC FINDINGS

  • Typically a mixture of mature fat and spindle cells.
  • The spindle cells
    • Arranged haphazardly, but tend to arranged in short, parallel bundles, often with nuclear palisading.
    • Are uniform with a single elongated nucleus and narrow, bipolar cytoplasmic processes. Nucleoli and mitoses are inconspicuous.
    • Background with mucoid material and collagen fibers.
  • Tumor may show predominant spindle cells or mature fat.
  • Mast cells in all cases.

IMMUNOPROFILE

  • CD34+, S100+ in mature fat, BCL2+, SMA-

CYTOGENETIC STUDIES

  • Del(16q) or del(13q)
  • Lack of giant marker and ring chromosomes.

DIFFERENTIAL DIAGNOSES

  • DFSP: storiform, no fat tissue.
  • Nodular fasciitis: more variable appearance, SMA+, CD34-.
  • Solitary fibrous tumor: patternless pattern, thin collagen fibers, no prominent adipose, CD99+, BCL2+, CD34-.
  • Atypical/well differentiated liposarcoma: deep soft tissue of abdomen and extremities, pleomorphic lipoblasts, giant marker and ring chromosomes.
  • Pleomorphic liposarcoma: extremitis, pleomorphic lipoblasts, metastasis.

TREATMENT AND PROGNOSIS

  • Completely benign lesion. Rarely recurs, even if incompletely excised.

REFERENCES: Enzinger and Weiss's Soft Tissue Tumors, 5th Edition. By Drs. Sharon Weiss and John Goldblum. 2007