Clinical Presentation
A 30-year-old male presented with a one-year history of right little
finger progressive paresthesia and a non-tender palpable enlarging mass
in the right axillary fossa.
MR neurography revealed a 30×25×24 mm heterogeneous, high-signal, round
mass within the right axillary fossa in proximity to the medial aspect
of brachial plexus branches. The mass showed high-signal intensity on T1
image, a very high T2 signal intensity and no signal drop on
fat-saturated sequence with the fluid-fluid level (Figure 1), indicating
a hemorrhage in the tumor. On operation a well-circumscribed ovoid,
solid, dark-blue tumor, originating from the ulnar nerve covered by the
nerve sheath was seen. Some nerve bundles were encased in the tumor with
no extra-neural invasion (Figure 2).
Frozen-section study revealed a small, round, blue cell tumor. Since all
motor functions of the ulnar nerve were intact, total tumor resection
with a wide margin of the surrounding soft tissue was done.
Histomorphological study (Figure 3) and IHC staining (Figure 4) revealed
a malignant, small, round, blue cell tumor, consistent with primitive
neuroectodermal tumor.