Rhabdomyosarcoma differential diagnosis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Suveenkrishna Pothuru, M.B,B.S. [2]

Overview

Rhabdomyosarcoma must be differentiated from Ewing sarcoma, Lymphadenopathy, Neuroblastoma, Liposarcoma Osteosarcoma, Lymphoprofilerative disorders. Rhabdomyosarcoma of the orbit must be differentiated from other causes of orbital masses such as orbital pseudotumor, orbital tumors, orbital abscess, and vascular lesions.

Differential Diagnosis

• Rhabdomyosarcoma must be differentiated from following diseases:

Disease	History/demography	Symptoms			Physical examination		Diagnosis
		Palpable mass	Pain	Others	Mass tenderness	Others	Genetics	Imaging		Histology
Rhabdomyosarcoma	Most common soft tissue cancer among children and adolescents The third most common extracranial solid tumors Two-third of all cases happen under 6 years old	+	+	Skin changes Respiratory difficulties Vomitting Hematuria	+/-	Fever Erythmatous skin Proptosis Ophtalmoplasia Dysconjugate gaze	Loss of heterozygosity of 11p15. Mutations in: TP53 NRAS KRAS HRAS PIK3CA CTNNB1 FGFR4 Translocations in PAX3 or PAX7 genes with FOXO1	CT scan: Soft tissue density Enhancement with contrast Bone destruction Ultrasound: Well-defined and irregular mass Low to medium echogenicity MRI: T1: Low to intermediate intensity Hemorrhage areas are poresent in alveolar rhabdomyosarcoma T2: Hyperintense Prominent flow voids are present in extremity lesions of rhabdomyosarcoma T1 C+ (Gd): Considerable enhancement		An appearance of round blue cell tumors Myogenesis pathway has various types of differentiation Positive immunohistochemical results for: myoglobin actin desmin Myogenin
Wilms tumor	Also called nephroblastoma The most common childhood abdominal malignancy Average age of 3.5 years old	+	+	Hematuria Respiratory symptoms ( due to lung metastases)	+/-	Fever Hypertension/ hypotension	Present mutations of: WT1 P53 FWT1 FWT2 11p15.5 loci	Ultrasound: The best initial diagnostic study. Distinguish tumor mass from other causes of renal swelling like hydronephrosis. Doppler ultrasonography can help to detect invasion of renal vein and IVC by the tumor. CT scan: Heterogeneous soft-tissue density masses Areas of calcification and fat-density regions Lymph node metastasis Surrounding organs invasion Thrombus in renal vein or inferior vena cava		Arises from mesodermal precursors of the renal parenchyma Well-circumscribed/ macrolobulated lesion Hemorrhage/ central necrosis may be present It is comprised of 3 types of cells: Stromal Epithelial Blastemal The stroma may include: Striated muscle cartilage bone Fat tissue Fibrous tissue.
Ewing sarcoma	Include ewing sarcoma, askin tumor, and peripheral primitive neuroectodermal tumors The second most common childhood malignant primary bone tumors Usually arises in the long bones of the extremities Common age between 10-20 years old	+	+	Weight loss/ fatigue	+	Fever Pathologic fractures Petachia/ purpura	Reciprocal translocation between chromosomes 11 and 22	Plain radiographic of region: Poorly marginated destructive lesion Permeative or "moth-eaten" appearance CT scan: Cortical destruction Demonstrate soft tissue disease MRI: Considered as a preferred diagnostic study Better shows tumor size/ intraosseous/extraosseous extent		Small/ round/ blue cell tumors May be undifferentiated or differentiated, Regular sized primitive appearing cells
Pediatric neuroblastoma	Most common extracranial solid tumor of infancy Arising from pluripotent sympathetic cells Age distribution: < 1 years old ( 40%) 1-2 years old (35%) > 2 years old (25%)	+ (Abdominal)	+	Constipation Weakness Diarrhea	+ (Abdominal)	Proptosis Periorbital ecchymosis Horner syndrome Opsoclonus myoclonus syndrome	Chromosome1p deletion N-myc amplification	CT scan: Heterogeneous mass Calcifications Necrotic areas MRI: T1: heterogeneous mass T2: heterogeneous/ hyperintense cystic/necrotic areas C+ (Gd): Heterogeneous mass		Well defined/ infiltrative mass Homer wright rosettes Secretion of vanillylmandelic acid (VMA) and homovanillic acid (HVA)
Pediatric pheochromocytoma	Rare catecholamine-secreting tumor Occur in both children and adults Average age of 11 years old Associated with neurofibromatosis, von Hippel-Lindau disease, tuberous sclerosis, Sturge-Weber syndrome, and multiple endocrine neoplasia (MEN) syndromes	-	+/-	Headache sweating Weakness Convulsion	-	Hypertension Tachycardia Pallor face	Genetic mutation in: NF1 RET VHL SDHD SDHC EGLN1 EGLN2 KIF1B SDHAF2 TMEM127 SDHA IDH1 SDHB MAX HIF2A FH	Ultrasound: Different appearance from solid to mixed cystic or solid to cystic CT scan: Large and heterogenous Calcification Necrosis Cystic changes MRI (in extra adrenal tumors): T1: Heterogenous enhancement Hypointense T2: Hyperintense T1 C+ (Gd): Heterogenous enhancement		Zellballen pattern on microscopy Well-defined clusters Eosinophilic cytoplasm Positive stains for: Chromogranin for zellballlen cells Neurospecific enolase markers for neuronal cells S-100 protein for sustentacular cells
Pediatric osteosarcoma	The second most common primary bone tumor The third most common tumor among adolescents Can be primary or secondary Primary osteosarcoma occurs in age of 10-20 years old Secondary osteosarcoma occurs in older patients and is secondary to paget disease and bone infarcts Accompanied with positive history of trauma	+	+	Soft tissue swelling Fracture Night sweating	+	Mass swelling Fever Arthritis Decreased joint range of motion Lymphadenopathy	Alteration in retinoblastoma gene (Rb)	Plain radiography: Osteolytic/ osteoblastic feature Periosteum reaction Calcification or ossification CT scan: Primary lesion and chest CT are required Demonstrate tumor location and extension MRI: Exact assessment of tumor extension Involving joint to joint findings		Contain various cellular pleomorphism and mitoses Poorly trabecular bone formation Fibrocystic and chondroblastic features
Pediatric liposarcoma	Considered as a nonrhabdomyosarcoma soft tissue sarcomas One of the least frequent tumors during childhood Rarely seen in adolescents and age of < 8 years old Average age is 50 years among adults Occur mostly in lower extremities, retroperitoneal region, and shoulder	+	+/-	Weight loss Fatigue	-	N/A	Amplification of 12q13–15 region in MDM2 and CDK4 genes Translocation of t(12;16)(q13;p11.2) in myxoid liposarcoma	CT scan: Inhomogenous fatty structure Tumor mineralization Cortical bone erosion Calcification Infiltration to medistinum MRI: Adipose content mass Thin irregular septa Hemorrhage Necrosis areas		Divided into following subtypes: Well-differentiated Dedifferentiated, Myxoid/roundcell Pleomorphic Common findings: Lipoblasts presence Cytoplasmic lipid vacuoles Chromatin spikes
Burkitt lymphoma		+/- (in non-endemic or sporadic form of the disease)	-	-	-	-		Abdominal ultrasonography may show splenomegaly and ascites.	Chest, abdomen, and pelvis CT scan may be helpful in the diagnosis of Burkitt's lymphoma but it is not done routinely.	On microscopic histopathological analysis, characteristic findings of Burkitt's lymphoma include: Medium-sized (~1.5-2x the size of a RBC) with uniform size ("monotonous") -- key feature (i.e. tumor nuclei size similar to that of histiocytes or endothelial cells) Round nucleus Small nucleoli Relatively abundant cytoplasm (basophilic) Brisk mitotic rate and apoptotic activity Cellular outline usually appears squared off "Starry-sky pattern": The stars in the pattern are tingible-body macrophages (macrophages containing apoptotic tumor cells. The tumour cells are the sky
Hydronephrosis		+	+/-	-	-	+ (CVA tenderness in case of pyelonephritis)		Ultrasound allows for visualization of the ureters and kidneys and can be used to assess the presence of hydronephrosis and/or hydroureter.	In the case of renal colic (one sided loin pain usually accompanied by a trace of blood in the urine) the initial investigation is usually an intravenous urogram. This has the advantage of showing whether there is any obstruction of flow of urine causing hydronephrosis as well as demonstrating the function of the other kidney. Many stones are not visible on plain x ray or IVU but 99% of stones are visible on CT and therefore CT is becoming a common choice of initial investigation.	The kidney undergoes extensive dilation with atrophy and thinning of the renal cortex.
Dysplastic kidney		N/A	N/A	N/A	N/A	N/A		MCDK is usually diagnosed by ultrasound examination before birth. Mass of non-communicating cysts of variable size. Unlike severe hydronephrosis, in which the largest cystic structure (the renal pelvis) lies in a central location and is surrounded by dilated calices, in multicystic dysplastic kidney the cyst distribution shows no recognizable pattern. Dysplastic, echogenic parenchyma may be visible between the cysts, but no normal renal parenchyma is seen.	MCKD can be discovered accidentally on CT scan. CT scan shows myltiple cysts with absence of renal parenchyma.	MCKD is the result of abnormal differentiation of the renal parenchyma.
Mesoblastic nephroma		+	+	-	+	-		Ultrasound may be helpful in the diagnosis of mesoblastic nephroma. Mesoblastic nephroma may presents as a well-defined mass with low-level homogeneous echoes. The presence of concentric echogenic and hypoechoic rings can be a helpful diagnostic feature of mesoblastic nephroma.	CT scan may be helpful in the diagnosis of mesoblastic nephroma. Findings on CT scan suggestive of mesoblastic nephroma include: Solid hypoattenuating renal lesion Variable contrast enhancement No calcification	Classic mesoblastic nephroma Spindle cells in fascicles Infiltrative border Cellular mesoblastic nephroma Plump cells with vesicular nuclei Well-defined border Mitotically active Mixed mesoblastic nephroma Both classic pattern and cellular pattern areas are present