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Presented by Dr. Ashley Cimino-Matthews and prepared by Dr. Jason Kern
Case 2: Retroperitoneal mass in a 50 year old female
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1. Question
Week 628: Case 2
Retroperitoneal mass in a 50 year old female
Correct
Answer: Dedifferentiated liposarcoma
Histology: Surgical resection of the retroperitoneal mass shows a tumor comprised of large, pleomorphic and atypical cells with hyperchromatic, irregular nuclei and numerous mitotic figures. There is no overt lineage of differentiation or low grade component. An immunostain for MDM2 shows positive nuclear labeling in the atypical cells.
Discussion: Although a well-differentiated component is not present, the MDM2 positivity supports diagnosis as a dedifferentiated liposarcoma. Of note, the lesion grossly measures 20 cm, so it is possible that a well-differentiated component was not sampled in the sections, or that the well-differentiated component had simply been overrun by the dedifferentiated component. Liposarcoma is the most common sarcoma in adults and most commonly involves the retroperitoneum, as in this case. There are three main subtypes of liposarcoma, including the well-differentiated/dedifferentiated, the myxoid/round cell, and the pleomorphic liposarcomas. Each subtype has different genomic aberrations.
The well differentiated/dedifferentiated liposarcomas show MDM2 and CDK4 amplification due to amplification of chromosome 12q13-15; thus, immunohistochemistry for MDM2 is useful in this setting (but is not 100% specific). Myxoid/round cell liposarcomas are translocation sarcomas that characteristically display a t(12;16) translocation between FUS-DDIT3 (TLS-CHOP) and less commonly a t(12;22) translocation between EWSR1-DDIT3. Pleomorphic liposarcomas have complex karyotypes reflected in the markedly pleomorphic nature of the cells. Morphologically, the lesion in this case is very atypical and the differential diagnosis for any pleomorphic, spindled-epithelioid lesion includes a variety of sarcomas, melanoma, and even pleomorphic carcinoma. Given the retroperitoneal location of the tumor, a liposarcoma is high on the differential. Although the markedly pleomorphic cells raise the possibility of pleomorphic liposarcoma, the MDM2 positivity supports classification as a dedifferentiated liposarcoma.
References:
1. Binh MB, Sastre-Garau X, Guillou L, et al. MDM2 and CDK4 immunostainings are useful adjuncts in diagnosing well-differentiated and dedifferentiated liposarcoma subtypes: a comparative analysis of 559 soft tissue neoplasms with genetic data. Am J Surg Pathol. 2005 Oct;29(10):1340-7.
2. Henricks WH, Chu YC, Goldblum JR, Weiss SW. Dedifferentiated liposarcoma: a clinicopathological analysis of 155 cases with a proposal for an expanded definition of dedifferentiation. Am J Surg Pathol. 1997 Mar;21(3):271-81.Incorrect
Answer: Dedifferentiated liposarcoma
Histology: Surgical resection of the retroperitoneal mass shows a tumor comprised of large, pleomorphic and atypical cells with hyperchromatic, irregular nuclei and numerous mitotic figures. There is no overt lineage of differentiation or low grade component. An immunostain for MDM2 shows positive nuclear labeling in the atypical cells.
Discussion: Although a well-differentiated component is not present, the MDM2 positivity supports diagnosis as a dedifferentiated liposarcoma. Of note, the lesion grossly measures 20 cm, so it is possible that a well-differentiated component was not sampled in the sections, or that the well-differentiated component had simply been overrun by the dedifferentiated component. Liposarcoma is the most common sarcoma in adults and most commonly involves the retroperitoneum, as in this case. There are three main subtypes of liposarcoma, including the well-differentiated/dedifferentiated, the myxoid/round cell, and the pleomorphic liposarcomas. Each subtype has different genomic aberrations.
The well differentiated/dedifferentiated liposarcomas show MDM2 and CDK4 amplification due to amplification of chromosome 12q13-15; thus, immunohistochemistry for MDM2 is useful in this setting (but is not 100% specific). Myxoid/round cell liposarcomas are translocation sarcomas that characteristically display a t(12;16) translocation between FUS-DDIT3 (TLS-CHOP) and less commonly a t(12;22) translocation between EWSR1-DDIT3. Pleomorphic liposarcomas have complex karyotypes reflected in the markedly pleomorphic nature of the cells. Morphologically, the lesion in this case is very atypical and the differential diagnosis for any pleomorphic, spindled-epithelioid lesion includes a variety of sarcomas, melanoma, and even pleomorphic carcinoma. Given the retroperitoneal location of the tumor, a liposarcoma is high on the differential. Although the markedly pleomorphic cells raise the possibility of pleomorphic liposarcoma, the MDM2 positivity supports classification as a dedifferentiated liposarcoma.
References:
1. Binh MB, Sastre-Garau X, Guillou L, et al. MDM2 and CDK4 immunostainings are useful adjuncts in diagnosing well-differentiated and dedifferentiated liposarcoma subtypes: a comparative analysis of 559 soft tissue neoplasms with genetic data. Am J Surg Pathol. 2005 Oct;29(10):1340-7.
2. Henricks WH, Chu YC, Goldblum JR, Weiss SW. Dedifferentiated liposarcoma: a clinicopathological analysis of 155 cases with a proposal for an expanded definition of dedifferentiation. Am J Surg Pathol. 1997 Mar;21(3):271-81.
