A 30-year-old female presented with complain of swelling over left elbow for 2 years. It was associated with mild pain and showed gradual increase in size. No other known co-morbids. No family history for malignancy.
On examination a solitary, firm and tender lump was palpable. Systemic examination was unremarkable.
MRI examination showed an abnormal signal intensity lesion along the medial aspect of elbow joint adjacent to the ulnar olecranon process, involving flexor carpi ulnaris and flexor digitorum profundus. The lesion appears mildly hyperintense to muscle with some focal prominent hyperintensities on T1. It appears hyperintense on T2 and T2 FAT SAT images. It shows heterogeneous post-contrast enhancement. The lesion is infiltrating the subcutaneous fat with small interface between skin and tumour. The ulnar nerve is also infiltrated by the tumour. It is closely abutting the ulnar bone however, no cortical break or abnormal bone signals noted. No involvement of the elbow joint noted.
Soft tissue tumours of elbow are rare, the incidence documented is around 3.8 % [1]. Most of the soft tissue tumours around elbow joint are benign [2], although malignant tumors are rare, they do occur with unique clinical and histopathological characteristics. Management of such tumours is challenging. Careful reporting, histological diagnosis and treatment is necessary for a better clinical outcome. Missed or delayed diagnosis can lead to bad outcomes. [3]
Clear cell sarcomas are a rare type of soft tissue sarcomas that occur in almost 50% in the lower extremities followed by upper extremities and rarely in the neck or trunk [4]. It predominantly affects younger age group with a female predilection [5]. It is aggressive in nature and morphologically shares features of melanoma, but unlike melanoma, it has chromosomal translocation of t(12:22)(q13:q12) which affects EWSR1-ATF1 gene.[6-7]
MR imaging with contrast administration is regarded as the best tool in characterizing the tumour along with neurovascular involvement, extent, staging and also for the preoperative assessment [8]. Literature search shows great variability of clear cell sarcoma signals on T1 and T2W images appearing variably low to high. Paramagnetic effect of melanin present in these tumours causes T1 shortening due to which they appear bright, however on T2 images, these appear low. [9] Tumour may show both T1 and T2W hypointense signals and no intracellular melanin may be present under the microscope.[10] Due to this variability of signals preoperative diagnosis using MR may be limited.
In this case hyperintense signals on T1 and T2W images were identified. Microscopically sections from the specimen exhibit a lesion in the deeper subcutaneous tissue. Higher magnification reveals compact nests or fascicles of fusiform or spindle-shaped cells that have oval to elongated vesicular nuclei and variably prominent nucleoli, resembling melanoma cells. Intracytoplasmic melanin pigment was not appreciated. The tumour cells showed a positive expression for immunohistochemical stains, S-100, Sox-10 and Melan-A. EWSR gene rearrangement in the tumour was detected on FISH studies.
On histopathology, no specific markers are used for its diagnosis. The molecular genetic testing for clear cell carcinoma has proved its role (8). Chromosomal translocation has been seen with clear cell sarcomas. In this case, molecular testing showed 22q12 translocation. This translocation has not been described in melanomas.
Though the gold standard for diagnosis of soft tissue sarcomas is histopathology, imaging features can help us to support and narrow down differential diagnosis to guide the surgeons. T1 hyperintense signals on MR examination call out to have a strong differential of malignant melanoma, however, being confined to the soft tissues with no or less involvement of the overlying epidermis can be of help. T1 hyperintense signals can also be seen in intratumoral haemorrhage, which is a pitfall and should be included in the list of differentials in correct clinical scenarios. As stated above clear cell sarcoma is a malignant mesenchymal tumour, the outcome of clear cell sarcomais poor with high rates of recurrence of pulmonary metastasis in 40% or lymph node metastasis in at least 30-50% of patients. Metastases often occur more than a decade after initial diagnosis. Tumour size > 5cm, necrosis, and regional lymph node involvement are unfavourable prognostic factors. Awareness of this rare tumour is crucial and suspicion can be raised in masses located in deep-seated sites in the extremity and this entity may be put in the differential diagnosis. However. role of MRI to diagnose it is still low due to signal variability.
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Clear cell sarcoma
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The patient is a 30-year-old female with a two-year history of swelling in the left elbow, mild pain, and gradual enlargement of the mass. Based on the provided MRI images, there is a space-occupying lesion within the soft tissue near the left elbow joint, with relatively distinguishable boundaries, presenting as a well-defined soft tissue mass. The lesion shows high signal intensity on T1-weighted imaging and relatively high signal intensity on T2-weighted imaging. The notes suggest the lesion may contain special components internally (e.g., melanin or hemorrhage), and a certain degree of contrast enhancement is observed. The surrounding neurovascular bundles appear to be intact; however, careful attention should be paid to local infiltration and soft tissue involvement.
The lesion is located in the deeper layer of the subcutaneous tissue and is partially adjacent to the muscle fascia. The overall edge is relatively clear, but its potential invasiveness should be evaluated in conjunction with the lesion’s biological characteristics.
These are the primary differential diagnoses in this case, as they can all present as soft tissue masses with possible high T1 signal.
Based on the patient's age, clinical presentation (slow growth with minimal pain but progressive enlargement), MRI findings (high signal on T1- and T2-weighted images), and pathological and molecular testing (immunohistochemistry positive for S-100, Sox-10, and Melan-A, as well as EWSR gene translocation), the most consistent diagnosis is Clear Cell Sarcoma.
If further clarification of tumor extent and potential metastasis is required, more precise imaging evaluations (such as whole-body PET-CT) or arthroscopy/biopsy around the lesion could be considered to rule out other rare tumor types.
After determining the tumor treatment plan, rehabilitation should be tailored to the surgical site and the patient’s overall condition, emphasizing individualization and safety.
Throughout the rehabilitation process, close follow-up is essential to promptly detect any signs of recurrence or metastasis and to ensure balance between safety and rehabilitation progress.
This report is based on the current imaging and pathological data for reference only and cannot replace a face-to-face diagnosis or professional medical opinion. Specific treatment plans and rehabilitation programs should be determined by specialist physicians based on individual patient conditions. If you have any questions or changes, please consult your clinical medical team promptly.
Clear cell sarcoma
