Myoepithelioma within the carpal tunnel: a case report and review of the literature

Abstract

Myoepitheliomas of the extremity are rare and usually benign, while a minority display malignant features. This case demonstrates the diagnosis and management of myoepithelioma within the carpal tunnel. Clinical and radiological tumour features were evaluated. Hematoxylin and eosin stained tumour sections were examined, and immunohistochemistry was performed. Histology revealed a nodular mass of epithelioid cells in clusters within a myxoid/chondroid stroma. No mitoses were noted. Cytokeratins, neuron-specific enolase, synaptophysin, glial fibrillary acidic protein, and S100 were positive on immunohistochemistry. A literature review revealed very few prior reports of myoepithelioma in the wrist, and limited data concerning any relationship between recurrence and quality of surgical margins. In this case, wide local excision would have significantly compromised dominant hand function, and therefore a marginal excision was deemed appropriate in the context of bland histological features. Surgical margins noted in future case reports will aid clinical decision making.

Figure 1

Thallium-201 scintigraphy at a) 30 minutes demonstrates focal uptake in the right wrist (arrow), and b) at four hours, wash-out in this area had occurred.

Figure 2

MRI of the lesion (L) shows it a) attached to the index finger profundus tendon in the coronal plane on T1 weighted imaging, b) demonstrating septal enhancement post contrast administration, c) displacing the superficialis tendons (T) to the middle and index fingers radially on axial T1 imaging, and d) showing heterogeneous T2 hyperintensity again in the axial plane, with the compressed median nerve (N) more clearly visualised.

Figure 3

Histopathology of the excisional biopsy specimen demonstrates a) lobules of chondroid/myxoid matrix with embedded vacuolated cells and plasmacytoid cells (100×), b) these same cell populations are shown at high-power (400×), c) positive cytokeratin AE1-3 staining (200×), and d) weak GFAP staining (200×).