Small Round Cell Tumors of Soft Tissue and Bone

Abstract

Context.— Small round cell tumors of soft tissue and bone constitute a divergent group of neoplasms. These lesions often demonstrate overlapping clinical and radiologic characteristics and share histomorphologic and sometimes immunophenotypic similarities, but they typically have diverse prognostic outcomes, thus warranting different clinical management. Recent advances in molecular and cytogenetic techniques have identified a number of novel molecular alterations contributing to the diversity of these lesions. This state-of-the-art knowledge has enhanced our understanding of these diseases. Objective.— To provide an overview of the current concepts in the classification and diagnosis of small round cell tumors of soft tissue and bone, focusing on salient histologic features, key immunophenotypic characteristics, and recent molecular genetic advancements. Data Sources.— Data were obtained from pertinent peer-reviewed English-language literature and firsthand experience from the authors as practicing bone and soft tissue pathologists. Conclusions.— Immunohistochemistry plays a vital role in rendering a specific diagnosis or narrowing the differential diagnosis in small round cell tumors of soft tissue and bone. Molecular genetic studies are often needed, especially for those lesions with unusual histologic features, an uncommon immunoprofile, and/or unusual clinical presentation. Accurate diagnosis of these tumors necessitates recognition of salient histologic features, judicious and astute use of ancillary studies, and correlation with the clinical and radiologic characteristics to guide clinical decision-making.

Cutaneous Metastasis of Alveolar Rhabdomyosarcoma in a Child

“…Table 2 presents a summary of the most common SRBCT that may arise in the head and neck region of children along with a list of key initial immunohistochemical markers frequently used for their diagnosis and classification. 21–23 In the present case, however, the history of a primary RMS combined with the histopathological features suggested a cutaneous metastasis. This hypothesis was confirmed using a single immunohistochemical marker (desmin) and a genetic panel, which not only allowed for a more expedited workup of this patient, but also optimized the utilization of resources.…”

The Challenges and Opportunities of Translational Pathology

“…This is particularly true in hematological, bone and soft tissue and urological pathology. 7 - 9 For example, fumarate hydratase–deficient renal cell carcinoma and microphthalmia transcription factor (MiTF) family translocation–associated renal cell carcinomas are no longer part of type 2 papillary renal cell carcinoma, according to the 2016 edition of the World Health Organization (WHO) genitourinary tumor classifications. 9 A host of emerging molecular genetic/genomic markers have also been discovered and utilized for diagnosing and/or treating sarcomas, lymphomas and leukemias.…”

“… 9 A host of emerging molecular genetic/genomic markers have also been discovered and utilized for diagnosing and/or treating sarcomas, lymphomas and leukemias. 7 , 8 One of the most exciting developments in this area is the discovery of pan-cancer biomarkers (also known as tumor-agnostic markers). These include microsatellite instability , tumor mutation burden and neurotrophic receptor kinase fusions, each of which are rather tumor-specific and have corresponding therapeutics (immunotherapy for the first two markers and NTRK inhibitors for the latter).…”

Ewing Sarcoma and Ewing-Like Sarcoma and the Role of NKX2.2 Immunoreactivity

“…But the importance of proper diagnosis is critical as many in this class are highly aggressive malignant tumors. The typical pathologic findings of tumors in this class include small round, hyperchromatic undifferentiated cells that have an increased nuclear-to-cytoplasmic ratio [ 1 ].…”

“…ES classically has a type III margin, meaning that it is permeative [ 3 ]. Additionally, the lesion characteristic for ES appears osteolytic with a multilayer periosteal reaction that is commonly referred to as “onion skin-like appearance” [ 1 ]. For ES, radiographic imaging is the current method for assessing tumor burden at diagnosis, monitoring response to therapy, and detecting disease recurrence.…”