Primary cutaneous sarcomas showing rhabdomyoblastic differentiation

Area of Science:

• Dermatopathology
• Pediatric Oncology
• Skeletal Muscle Neoplasms

Background:

• Rhabdomyosarcoma is a rare soft tissue neoplasm, typically affecting children and adolescents, with common sites including the head/neck, genitourinary tract, and extremities.
• Primary cutaneous rhabdomyosarcoma is exceptionally rare, with limited reports in existing literature.

Observation:

• This report details two cases of primary cutaneous rhabdomyosarcoma: an embryonal type in a 9-year-old girl and a solid alveolar variant in an 86-year-old man.
• Tumors presented as solitary, plaque-like or nodular skin lesions on the nose and chest wall, respectively.
• One case showed malignant 'triton' tumor features upon recurrence, with S-100 positive spindle cells alongside rhabdomyoblastic components.

Findings:

• Histopathological and immunohistochemical analyses confirmed rhabdomyoblastic differentiation, with positive staining for muscle-specific actin, desmin, and vimentin in both cases.
• Ultrastructural examination revealed intermediate filaments consistent with rhabdomyoblastic differentiation.
• Both patients experienced multiple local recurrences over 2-4 years despite surgical excision; the older patient also developed axillary lymph node metastasis.

Implications:

• Primary cutaneous rhabdomyosarcoma must be considered in the differential diagnosis of small blue cell tumors and undifferentiated skin neoplasms.
• Accurate diagnosis necessitates comprehensive immunohistochemical studies and, in select cases, electron microscopy.
• The aggressive nature and high recurrence rate underscore the need for vigilant follow-up and potentially multimodal treatment strategies.