Well-differentiated spindle cell liposarcoma (‘atypical spindle cell lipomatous tumor‘) does not belong to the spectrum of atypical lipomatous tumor but has a close relationship to spindle cell lipoma: clinicopathologic, immunohistochemical, and molecular analysis of six cases

Abstract

Well-differentiated spindle cell liposarcoma represents a rare atypical/low-grade malignant lipogenic neoplasm that has been regarded as a variant of atypical lipomatous tumor. However, well-differentiated spindle cell liposarcoma tends to occur in subcutaneous tissue of the extremities, the trunk, and the head and neck region, contains slightly atypical spindled tumor cells often staining positively for CD34, and lacks an amplification of MDM2 and/or CDK4 in most of the cases analyzed. We studied a series of well-differentiated spindle cell liposarcomas arising in two female and four male patients (age of the patients ranged from 59 to 85 years). The neoplasms arose on the shoulder, the chest wall, the thigh, the lower leg, the back of the hand, and in paratesticular location. The size of the neoplasms ranged from 1.5 to 10 cm (mean: 6.0 cm). All neoplasms were completely excised. The neoplasms were confined to the subcutis in three cases, and in three cases, an infiltration of skeletal muscle was seen. Histologically, the variably cellular neoplasms were composed of atypical lipogenic cells showing variations in size and shape, and spindled tumor cells with slightly enlarged, often hyperchromatic nuclei. Multivacuolated lipoblasts were present in three neoplasms. Focal myxoid stromal changes were seen in three cases. Immunohistochemically, CD34 was at least focally positive in all cases, whereas scattered tumor cells only showed a nuclear expression of MDM2 in two neoplasms. FISH analysis revealed a deletion of the Rb-1 gene in all six cases, whereas no MDM2/CDK4 amplification was identified in all cases tested. Follow-up information was available in four cases (range from 4 to 24 months), and revealed a local recurrence in one case. Although well-differentiated spindle cell liposarcoma and atypical lipomatous tumor behave clinically similar, it can be speculated on the basis of clinicopathologic and molecular findings that welldifferentiated spindle cell liposarcoma may constitute an independent entity rather than a morphologic variant of atypical lipomatous tumor, and may represent the atypical/low-grade counterpart of spindle cell lipoma. Modern Pathology (2010) 23, 729-736; doi:10.1038/modpathol.2010 published online 12 March 2010 Keywords: liposarcoma; atypical lipomatous tumor; spindle cell liposarcoma; spindle cell lipoma; immunohistochemistry; cytogenetics Atypical and malignant lipogenic neoplasms represent the most common soft tissue sarcoma in adults, accounting for approximately 20% of all sarcomas. Liposarcoma is currently subclassified into five main subtypes, including atypical lipomatous tumor/well-differentiated liposarcoma, dedifferentiated liposarcoma, myxoid liposarcoma,

Recently characterized soft tissue tumors that bring biologic insight

“…In contrast to conventional atypical lipomatous tumor, staining for MDM2 and CDK4 is most often negative. This latter result is in line with more recent genetic data, 28,29 which have proposed that these tumors show either monosomy of chromosome 7 or, as suggested by Mentzel et al, 16 rearrangement of 13q. In our experience, the latter finding seems to be most accurate and this may be further supported by loss of Rb protein expression (Figure 8).…”

Malignant dermatofibroma: clinicopathological, immunohistochemical, and molecular analysis of seven cases

“…[23][24][25] Given the fact that premalignancy represents a biological rather than a morphological concept, 26 it is not surprising that a small group of premalignant mesenchymal neoplasms exist, which may progress to sarcomas with metastatic potential but have not attained all morphological features of malignancy at the time of first presentation.…”

Posterior Neck Triangle Spindle Cell Lipoma

“…CD34 immunoreactivity can also be demonstrated in atypical lipomatous neoplasms and well-differentiated liposarcomas [4,12]. Therefore, CD34 expression alone is not pathologically diagnostic of SCL, but can aid the pathologist in making the diagnosis.…”

“…Further definition of an SCL is they are atypical benign lesions, composed of atypical adipocytes with varying shaped and sized hyperchromatic nuclei associated with slightly atypical spindle-shaped cells [4].…”