The Small Round Cell Sarcomas Complexities and Desmoplastic Presentation

Abstract

<b><i>Background:</i></b> Small round cell sarcomas (SRCSs) account for most solid malignancies in the pediatric age group and are a part of group of malignant tumors characterized by heterogenous clinical presentation and overlapping microscopic features of small, round, primitive cells. In addition to the recently established certain genetically defined subset of undifferentiated round cell sarcomas of soft tissue and bone, this group of sarcomas include desmoplastic small round cell tumor, poorly differentiated synovial sarcoma, alveolar rhabdomyosarcoma, mesenchymal chondrosarcoma, and small cell osteosarcoma. Although, those entities share clinical and cytomorphologic features and cannot be unequivocally classified based on clinical presentation and morphology alone. Most of SRCSs characterizes of particular patterns of protein expression or genetic changes and ancillary tests remain necessary to confirm or rule out a specific diagnosis. Subtle but occasionally distinctive cytologic features narrows the number of differential diagnoses and helps to select appropriate ancillary tests necessary for the final diagnosis. Thus, when adequate fine needle aspiration (FNA) biopsy specimen is combined with ancillary tests, a specific histologic diagnosis can be made in almost all cases. However, due to complex cytologic features of SRCS as well as various quality and diversity of FNA smears, there are cases in that cytologic features which do not entirely match the known diagnostic criteria. <b><i>Summary:</i></b> The aim of this review was to summarize cytomorphologic criteria and to present rare and divergent cytological features of SRCSs. Careful assessment of clinical presentation, cytological features, immunohistochemical patterns, and molecular alternations is necessary for an accurate diagnosis. Knowing of rare and divergent microscopic findings that does not fit with the known cytological criteria will help to avoid misdiagnosis. <b><i>Key Messages:</i></b> The role of FNA biopsies diagnosing soft tissue and bone tumors has been increasing because of the ability of ancillary tests to assist in the diagnosis of specific tumors. SRCSs may be diagnosed accurately in cytology specimens. Access to clinical and radiographic presentation, utility of ancillary tests, understanding complexity of cytological features, and awareness of the rare cytologic findings that differ from that of the established diagnostic criteria are essential to make correct diagnosis.

Case report: Lymph node metastasis of pelvic alveolar rhabdomyosarcoma diagnosed by fine needle aspiration cytology

“…However, a reliable subclassification of RMS cannot be made only by FNA smears due to the lack of histological structure. Moreover, the ARMS also needs to be differentiated from other small blue-round cell tumors, including lymphoma, Ewing/PNET, neuroblastoma, and desmoplastic small round tumors ( 5 ). The rhabdoid feature can provide a hint and help with the differential diagnosis, which is more obvious on the cell block sections.…”

“…ARMS occurs most frequently in the deeper parts of the extremities and can also involve the trunk, perineum, and pelvis. In terms of age, ARMS accounts for approximately 20% of all pediatric RMS and is most common in adolescents and young adults between the ages of 10 and 25 ( 5 ).…”

Needle preceding the scalpel in soft-tissue sarcomas – A case series

“…Other small cell malignant tumors such as lymphomas, blastemal tumors, and small cell carcinomas should be considered as differentials for SRCSs. 14 ES includes undifferentiated SRCS of bone and soft tissue including round cell sarcomas with EWSR1-non-ETS fusions, CIC-rear-ranger sarcomas, and sarcomas with BCOR genetic alterations. The peripheral PNET was used when ES displayed neuroectodermal differentiation.…”

“…As both tumors share the same molecular profile, the term PNET is not used now. 14,15 ES family of tumors are highly aggressive tumors common in the first and second decade of life. However, studies have reported them in elderly age group also.…”

Chemotherapeutic drugs for soft tissue sarcomas: a review

“…The first-line chemotherapy drug for pleomorphic rhabdomyosarcoma and adult spindle cell rhabdomyosarcoma is usually doxorubicin ( Gallego et al, 2021 ; Gronchi et al, 2021 ), and for other subtypes include ifosfamide, vincristine, actinomycin D, doxorubicin, cyclophosphamide, and vinorelbine ( Walterhouse et al, 2014 ; Walterhouse et al, 2017 ; Bisogno et al, 2019 ; Schoot et al, 2022 ; Bisogno et al, 2023 ). Ewing sarcoma family of tumors are considered main members of small round cell sarcomas ( Rajwanshi et al, 2009 ; Marino-Enriquez and Fletcher, 2014 ; Domanski, 2022 ; Gajdzis et al, 2022 ). Vincristine, doxorubicin, cyclophosphamide, ifosfamide, and etoposide are the first-line drugs recommended for Ewing sarcomas ( Brennan et al, 2022 ).…”