A 59-year-old woman presented with a plantar foot mass that is present for 15 years. She has a history of a tumour debulking surgery 12 years ago. The mass is painful when standing or walking.
Radiographs demonstrate well-defined erosions of the cuboid, navicular, anterior calcaneus, and intermediate and lateral cuneiforms.
Axial PD FS and sagittal T2 FS MR images demonstrate a lobulated, mildly heterogeneous, hyperintense lesion in the deep plantar soft tissue of the foot, with erosion into the surrounding bones. The mass has heterogeneous, primarily low T1 signal intensity. The mass partially encases the flexor hallucis longus and flexor digitorum longus tendons. Contrast-enhanced T1 images show diffuse enhancement of the mass.
Histopathology images at low and high magnification show nests of epithelioid cells on a background of myxoid and chondroid stroma.
Chondroid syringoma (CS), also known as cutaneous mixed tumour, is a skin appendageal tumour of sweat gland origin, usually found in the head and neck region and much less commonly found in the extremities [1]. CS has an incidence of <0.098% and most commonly affects middle-aged or older males [2]. CS is morphologically identical to pleomorphic adenoma of the salivary glands.
The typical presentation is a slow-growing, firm nodule in the dermis or subcutaneous fat. Prior case reports have shown a heterogeneous T2 hyperintense and T1 hypointense mass on MRI, with enhancement following contrast administration [1,2]. While it is most commonly benign, rare cases have been shown to be malignant [3]. Since malignant CS is uncommon, there are currently no concrete criteria to determine benign versus malignant CS when analyzing histopathology [4].
At pathology, there is extensive chondroid and/or myxoid stroma, with nests of epithelioid cells that have abundant eosinophilic cytoplasm and vesicular nuclei [5].
Whether benign or malignant, it has been found that surgical excision with wide margins is often curative [5], with no requirement for radiation or systemic therapy for benign disease. Once excised, the sample can be analyzed for evidence of malignancy. Although there are no well-defined criteria for malignant CS, findings such as pleomorphism, mitoses, and cytoplasmic atypia may indicate malignancy [3]. Adjuvant radiation therapy has been utilized in the treatment of rare malignant tumours [3]. In this case, there were no features of malignancy, and the patient had no evidence of tumour recurrence on one-year follow-up MRI.
As a skin appendageal tumour, chondroid syringoma is uncommonly a radiologic diagnosis. However, due to the potential for deep growth, CS can be included in the differential diagnosis for an infiltrative mass in the extremities.
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Benign chondroid syringoma
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A soft tissue mass shadow is visible in the patient’s right plantar region, with relatively clear boundaries. There is local soft tissue proliferation accompanied by varying degrees of swelling. X-ray imaging shows that the continuity of the metatarsal and tarsal bones is intact, without obvious signs of bone destruction or fracture, and a dense shadow can be seen in the adjacent soft tissue. MRI indicates the lesion is located within the plantar soft tissue layer, presenting low or iso-intensity on T1-weighted sequences and high signal intensity on T2-weighted sequences. Contrast-enhanced scans show marked enhancement, suggesting certain soft tissue tumor characteristics.
Considering the patient’s age, clinical presentation (chronic plantar foot pain, pain while standing and weight-bearing), surgical history, imaging findings (high T2 signal and significant contrast enhancement), and pathological results (presence of cartilaginous matrix and skin appendage epithelial components), the most likely diagnosis is Chondroid Syringoma (Mixed Tumor of Soft Tissue). Currently, the lesion shows benign characteristics with no clear signs of malignancy.
If the lesion enlarges again, pathology indicates malignancy, or recurrence is observed, further evaluation or a more extensive resection, possibly combined with radiation therapy, may be considered.
Treatment Strategy:
Rehabilitation and Exercise Prescription (FITT-VP Principle):
Important Precautions:
Disclaimer: This report is provided for informational purposes only and is not a substitute for in-person medical consultation or professional diagnosis and treatment. If you have any questions or changes in your condition, please seek medical advice promptly.
Benign chondroid syringoma
