Myxoid liposarcoma: Fine-needle aspiration cytopathology in the molecular era. A report of 24 cases.

Background: Application of fine-needle aspiration (FNA) biopsy to soft tissue tumors remains underutilized in North America. Myxoid liposarcoma (LPS), the second most common subtype of LPS, is characterized primarily by t(12;16)(q13;p11) which is amenable to FISH analysis using a break-apart probe for DDIT3. Little is known regarding FISH testing for DDIT3 on cytologic specimens. We report our FNA experience with myxoid LPS and application of this molecular probe.

Methods: Specimens retrieved from our cytology database used search codes for myxoid LPS. Tissue files were searched for any cases with corresponding FNA biopsies. FNA biopsy was performed using a standard technique.

Results: From 24 FNA cases of myxoid LPS (mean age = 52 years), a specific diagnosis was made in 87.5%. Two cases were diagnosed as spindle/round cell neoplasm, and 1 as suspicious for myxoid LPS. There were 2 false positive diagnoses and no false negatives. Nearly all cases arose in the extremities; thigh being most common. Principal cytologic features consisted of discrete myxocellular microfragments, a plexiform capillary pattern, and variable number of univacuolated lipoblasts. Uniformly banal ovoid nuclei were randomly scattered within myxocellular microfragments. FISH analysis for DDIT3 rearrangement from unstained smears and/or cell-block was positive in 13 cases, and unsuccessful in 3, with no false positive/false negative results.

Conclusions: Myxoid LPS is diagnosable in a high percentage of cases using FNA biopsy alone. Confirmatory FISH analysis for DDIT3 is not only possible, but also valuable for correctly recognizing this neoplasm.