A multidisciplinary sarcoma tumor board is reviewing the pathology of several young adult patients presenting with deep soft tissue and bone masses. To establish the definitive diagnosis and guide neoadjuvant therapy, the pathologist correlates the microscopic morphology and immunohistochemical (IHC) profiles with their defining molecular signatures. Match the following complex histopathologic and immunohistochemical biopsy descriptions with their corresponding definitive diagnoses and characteristic chromosomal translocations.
- A deep thigh mass biopsy reveals a dual population of primitive spindle cells and glandular-like epithelial structures. The tumor cells show strong nuclear expression of TLE1 and focal positivity for cytokeratin.Synovial sarcoma; t(X;18) causing SS18-SSX fusion
- An intramuscular calf lesion biopsy demonstrates prominent arborizing, delicate capillaries in an abundant basophilic, myxoid stroma, containing scattered cells with multiple cytoplasmic lipid vacuoles.Myxoid liposarcoma; t(12;16) causing FUS-DDIT3 fusion
- A deep aponeurotic mass in the foot shows nested aggregates of uniform, pale-staining cells separated by fibrous bands. Immunohistochemistry is strongly positive for S100 protein and HMB-45, but lacks BRAF mutations.Clear cell sarcoma of soft tissue; t(12;22) causing EWSR1-ATF1 fusion
- A rapidly enlarging extremity mass biopsy exhibits uniform, primitive round cells arranged in nests separated by thick fibrous bands. The cells in the center of the nests are discohesive. IHC shows strong nuclear myogenin expression.Alveolar rhabdomyosarcoma; t(2;13) causing PAX3-FOXO1 fusion
- A diaphyseal biopsy of a permeative bony lesion demonstrates dense sheets of uniform cells with scant cytoplasm, round nuclei, and indistinct nucleoli. Tumor cells show strong, diffuse membranous staining for MIC2 (CD99).Ewing sarcoma; t(11;22) causing EWSR1-FLI1 fusion
Cevap
The correct matches integrate the distinct morphologic descriptions and IHC markers with their pathognomonic translocations: The TLE1+ biphasic tumor is Synovial Sarcoma; the myxoid tumor with arborizing capillaries is Myxoid Liposarcoma; the deep S100/HMB-45+ mass is Clear Cell Sarcoma; the myogenin+ discohesive round cell tumor is Alveolar Rhabdomyosarcoma; and the CD99+ small round blue cell bone tumor is Ewing Sarcoma.
Each histopathologic description contains pathognomonic keywords directly linked to a specific sarcoma subtype and its defining cytogenetic abnormality. TLE1 and biphasic histology point to synovial sarcoma (t(X;18)). Chicken-wire vasculature with lipoblasts indicates myxoid liposarcoma (t(12;16)). Melanocytic markers in a deep mass without BRAF mutations denote clear cell sarcoma (t(12;22)). Pseudo-alveolar architecture with myogenin designates alveolar rhabdomyosarcoma (t(2;13)). Membranous CD99 in a bony small round cell tumor signifies Ewing sarcoma (t(11;22)).
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Anahtar Kavram
Integrating histomorphology, specific immunohistochemical staining patterns, and pathognomonic chromosomal translocations is essential for establishing the definitive diagnosis of soft tissue and bone sarcomas.