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A 13-year-old girl presents to a primary healthcare center in Saudi Arabia with swelling in her left arm. Six weeks previously, she had injured her arm in a fall while playing at school, which left her with significant superficial abrasions, but the swelling has gradually expanded.

General practitioners assessing her injury at the time of her fall had identified the swelling as a traumatic hematoma, and instructed her to apply ice packs and compression to the injured area.

She returns for reassessment when the recommended conservative measures have not stopped the swelling. The patient is otherwise healthy and has no history of prolonged bleeding; both her past medical and her family history identify nothing of note.

Clinicians examine the swelling, now 10 × 5 cm; it is tender, firm, and immobile, and the overlying skin appears normal.

An x-ray of the humerus from 4 weeks previously (performed 2 weeks after the injury) reveals a large soft tissue mass with areas of calcification. Clinicians also note irregular cortex and periosteal reactions, findings that had not been taken into account when the imaging was performed. Results of lab tests, including a coagulation profile, were normal.

A bedside ultrasound of the patient's left upper arm is performed by the family medicine physician, who has 5 years of experience in general ultrasound examinations. This identifies the swollen injured area as a hypoechoic mass, measuring 5.0 × 1.8 cm, with evidence of internal septation and increased vascularity. The underlying bone is irregular and shows a periosteal reaction, which based on the initial injury, had originally been interpreted as a subcutaneous hematoma with granulation tissue.

Given the prolonged duration and progressive nature of the swelling, clinicians refer the patient for an MRI of the arm to assess the lesion in greater detail.

The clinicians, however, perform the MRI without intravenous contrast, reporting that the patient is uncooperative. The image shows a large soft tissue mass located midshaft of the left humerus, 9.4 × 3.4 × 3.0 cm in size, and encasing the entire circumference of the diaphysis, protruding toward the front of the arm.

The signal intensity of the tissue resembles that of skeletal muscles on both T1- and T2-weighted images, and there is a heterogeneous area of high T2 and low T1 signal intensities seen in the diaphysis, characterized by an ill-defined margin and wide zone of transition. The edges of the lesion have an interrupted and irregular periosteal reaction, although the proximal and distal epiphyses are not affected.

Clinicians arrive at a presumptive diagnosis of high-grade osteosarcoma, and perform ultrasound-guided biopsy of the lesion after the patient is sedated. Histopathological examination shows broad sheets of small round cells with scant cytoplasm in a background having scant stroma; there is also evidence of coagulative necrosis and reactive new bone formation.

Immunohistochemistry testing is strongly positive for CD99, vimentin, and synaptophysin, but negative for cytokeratin, desmin, and CD45. This confirms the diagnosis of Ewing sarcoma, and a bone scan performed for staging shows no signs of distant metastases.

After referral to a specialized cancer center, the patient undergoes wide local resection, and reconstruction with a vascularized fibular graft after completion of a course of chemotherapy. Surgery is successfully completed with no complications, but it is noteworthy that the entire process delayed the diagnosis by about 6 months from the initial presentation.

Follow-up assessment at 12 months finds the patient well, and a radiograph shows that the humerus is properly aligned.

Discussion

The physician reporting this of a 13-year-old girl whose arm swelling due to Ewing sarcoma was misdiagnosed as a hematoma, despite the radiographic and sonographic findings, notes that such misdiagnoses of soft tissue tumors are unfortunately not unusual due to their rarity, wide range of clinical and histological presentations, and low index of suspicion by physicians.

That diagnosis of this patient was delayed for over 6 months from the time of initial presentation highlights the importance of prompt diagnostic evaluation by MRI and biopsy to avoid delayed treatment, the case author emphasizes.

Ultrasound examination does not allow sufficient accuracy to properly evaluate soft tissue masses, he notes, citing a review of of soft tissue tumors conducted by radiologists, which found that almost 25% were misdiagnosed, most commonly as hematoma.

Early referral to a specialized center can help reduce the mortality and morbidity associated with soft tissue sarcomas, since management often involves a multidisciplinary approach to treatments that may include chemotherapy, radiotherapy, and surgery.

Given that soft tissue hematoma due to trauma typically regresses over time, patients with a solid mass that persists beyond 4 weeks should have a proper diagnostic evaluation, the author writes; tumors less than 5 cm should be excised and biopsied, while larger tumors should be assessed with MRI followed by incisional biopsy.

Ewing sarcoma – the second most common malignant bone tumor in children – generally involves the long bones. Retrospective analysis of of 100 consecutive histopathologically proven cases of Ewing sarcoma found that the bones involved in order of frequency were long bones (n=38), rib (n=22), iliac bone (n=12), vertebrae (n=7), scapula (n=3), sacrum (n=3), craniofacial bone (n=3), clavicle (n=1), and extraosseous (n=11).

Sites of lesion other than the long bones, ribs, and pelvis were regarded as uncommon, accounting for 25% of the sample, the researchers wrote, adding that among pelvic bone lesions, sacral involvement is uncommon.

In the case of this patient, the author notes that radiologically, Ewing sarcoma presents as a destructive bone lesion with interrupted periosteal reaction, although uncommon radiological features have been reported in about 8% of cases. This patient's case involved one such uncharacteristic finding -- soft tissue calcification -- which represents debris of a periosteal bone reaction. MRI not only aids in diagnosis, but also allows for accurate anatomic analysis and biopsy planning.

The case author writes that given that delays may have a negative impact on a patient's outcome and experience, timely diagnosis of cancers is crucial, and in fact, missed diagnoses of cancer represent a leading cause of in primary care.

As patients' first point of contact within the healthcare system, primary care physicians have a vital role to play in shortening the diagnostic process by making . This may rely substantially on clinicians' history-taking skills, given the limited access to diagnostic tools, the author notes.

Conclusions

He concludes that this case of Ewing sarcoma mistaken for a traumatic hematoma highlights the need to consider soft tissue tumors as a differential diagnosis in patients who present with progressively expanding swelling, adding: "Primary care physicians should have a high index of suspicion for malignancies and should not be reluctant to refer patients for further investigations in cases exhibiting an unusual clinical course of the condition."

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