Primary intranodal epithelioid rhabdomyosarcoma

Area of Science:

• Oncology
• Pathology
• Head and Neck Surgery

Background:

• Primary epithelioid rhabdomyosarcoma is an exceptionally rare malignancy.
• Rhabdomyosarcoma typically arises in skeletal muscle but can occur in lymph nodes.
• Parotid gland masses require careful differential diagnosis, including rare neoplasms.

Observation:

• A 72-year-old male presented with a 5-cm mobile, nontender mass in the parotid tail and level II neck region.
• Positron emission tomography/computed tomography revealed a hypermetabolic soft tissue mass within the right parotid gland.
• Histopathology demonstrated an intraparotid lymph node effaced by a centrally necrotic epithelioid neoplasm with rhabdoid features.

Findings:

• Immunohistochemistry confirmed neoplastic cells expressed desmin and myogenin.
• Electron microscopy revealed features consistent with rhabdomyosarcoma, including sarcomeres.
• Genetic analysis for FOXO1, PAX3, and/or PAX7 rearrangements was negative.

Implications:

• This case highlights the importance of considering rare tumors in the differential diagnosis of parotid masses.
• Complete surgical resection and adjuvant chemotherapy can be effective treatment for this rare entity.
• Further research into the pathogenesis and optimal management of primary lymph node rhabdomyosarcomas is warranted.