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Thoracic Presentations of Small Round Blue Cell Tumors
Address for correspondence: Dr. Annalice Chang, Department of Radiology, Yale New Haven Hospital, 20 York St., New Haven, 06510 CT, USA. E-mail: annalice.chang@yale.edu
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Abstract
The term “small round blue cell” is frequently used as a cursory radiologic pathological correlation of aggressive tumors throughout the body. We present a pictorial essay of common and uncommon subtypes of small round blue cell tumors in the chest illustrating the characteristic radiologic findings of each lesion. In addition, we review the pathologic findings of each tumor subtype with characteristic hematoxylin- and eosin-stained photomicrographs and immunohistochemical and molecular studies. Represented tumors include small cell carcinoma, Ewing sarcoma, extranodal marginal zone B-cell lymphoma, embryonal rhabdomyosarcoma, desmoplastic small round cell tumor, and posttransplant lymphoproliferative disorder. Understanding and ability to recognize these lesions are essential to broaden the radiologist's differential diagnosis and help guide patient care.
Keywords
Radiologic-pathologic correlation
small round blue cell tumors
thoracic small round blue cell tumors
INTRODUCTION
The term small round blue cell tumors (SRBCTs) refers to similar appearing neoplasms composed of small, round, basophilic cells on hematoxylin and eosin (H and E) staining. Within the thorax, many SRBCTs appear as nonspecific pulmonary nodules or masses on imaging. Therefore, accurate diagnosis relies on a combination of clinical presentation, radiographic studies, and pathologic specimens. In this pictorial essay, we present a radiologic and pathologic review of SRBCTs in the thorax highlighting the characteristic radiologic images, histomorphology, immunohistochemistry, and molecular studies utilized to arrive at the diagnosis. Represented tumors include small cell carcinoma, Ewing sarcoma, extranodal marginal zone B-cell lymphoma, embryonal rhabdomyosarcoma, desmoplastic small round cell tumor, and posttransplant lymphoproliferative disorder (PTLDs).
SMALL CELL LUNG CARCINOMA
Small cell lung carcinoma (SCLC) is a common, rapidly growing neoplasm that has a strong correlation with cigarette smoking.[1] Patients present clinically with a cough, hemoptysis, or postobstructive pneumonia.[1] Radiographically, SCLC presents as a centrally located bulky hilar/perihilar mass with associated adenopathy. Complications include displacement or narrowing of the tracheobronchial tree or vessels, pleural effusions, and/or metastases [Figure 1]. Histologically, SCLC is characterized by densely packed neuroendocrine cells with high mitotic activity. Positive immunostaining for chromogranin A or synaptophysin is confirmatory [Figure 2].
EWING SARCOMA
Ewing sarcoma commonly presents with nonspecific localized bony pain in children and adolescents. The most common locations include the pelvis, femur, spine, ribs, and skull.[2] Radiographically, they present as an osseous lesion with aggressive periosteal reaction and soft tissue mass.[23] Extra-osseous Ewing sarcoma can present in the thorax and arise from chest wall structures or soft tissues (Askin tumor), presenting as a pleural-based mass with an associated effusion.[3] Histologically, they are characterized by sheets of small round cells (or rarely spindled cells) [Figure 3]. Positive immunostaining for CD99 [Figure 4] and t(11;22)(q24;q12) chromosomal translocation are distinguishing features.
EMBRYONAL RHABDOMYOSARCOMA
Rhabdomyosarcoma is the most common childhood soft tissue tumor and often arises from the head, neck, and genitourinary system.[4] Isolated thoracic rhabdomyosarcomas are unusual but can arise from the heart, lungs, pleura, airways, or mediastinum.[4] Radiographically, they often present as a soft tissue mass, which erodes into the adjacent bone. Metastatic disease can present as pulmonary/pleural nodules [Figure 5]. The unifying histomorphologic feature is neoplastic cells that resemble embryonic skeletal myoblasts, which display positive immunostaining for myogenin and/or MyoD1 [Figure 6].
DESMOPLASTIC SMALL ROUND CELL TUMOR
Desmoplastic small round cell tumors are rare neoplasms which typically arise in the abdomen and present with abdominal pain.[5] Radiologic imaging demonstrates multiple abdominopelvic masses with a dominant mass arising from the retrovesical/retrouterine space.[5] Thoracic dissemination may manifest as pulmonary nodules or pleural involvement [Figure 7].[5] The defining histologic feature is that of desmoplastic stroma enveloping irregular nests of cells [Figure 8]. Positive immunostaining for vimentin [Figure 8] and t(11;22)(p13;q12) chromosomal translocation are distinguishing features.[6]
EXTRANODAL MARGINAL B-CELL LYMPHOMA
Extranodal marginal B-cell lymphoma or mucosa-associated lymphoid tissue, often arises from the gastrointestinal tract.[7] Within the lungs, they can present as metastatic disease or primary bronchial-associated lymphoid tissue lymphoma. Radiographically, they appear as lung nodules/masses or airspace consolidations [Figure 9].[8] Immunohistochemically, these neoplastic cells typically express IgM and stain strongly for CD20 [Figure 10].
POSTTRANSPLANT LYMPHOPROLIFERATIVE DISORDER
PTLDs are lymphoid or plasmacytic proliferations that develop as a consequence of immunosuppression following organ transplantation. The abdomen is most frequently involved. Thoracic manifestations are less common, presenting as randomly distributed pulmonary nodules [Figure 11].[9] A characteristic feature of PTLD is its association with Epstein–Barr virus infection, which can be detected by Epstein–Barr encoding region in situ hybridization [Figure 12].
DISCUSSION/CONCLUSION
SRBCTs are a heterogeneous group of aggressive neoplasms [Table 1]. Within the thorax, many of these lesions appear as nonspecific pulmonary nodules/masses radiographically and can be difficult to diagnose definitively without soft tissue sampling. On H and E staining, SRBCTs often appear similar, and immunohistochemistry and cytogenetics help distinguish between the entities. Understanding these lesions can broaden the radiologist's differential diagnosis and help guide patient care.
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Conflicts of interest
There are no conflicts of interest.
Available FREE in open access from: http://www.clinicalimagingscience.org/text.asp?2016/6/1/25/184539
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