Is cutaneous leiomyosarcoma a cancerous condition?

Cutaneous Leiomyosarcoma: A Malignant Skin Cancer

Yes, cutaneous leiomyosarcoma is definitively a cancerous condition that requires appropriate oncological management. 1, 2

Classification and Origin

Cutaneous leiomyosarcoma (CLM) is a rare malignant smooth muscle tumor that can arise from:

• Dermal layer: Originates from arrector pili muscles of hair follicles
• Subcutaneous layer: Arises from blood vessel smooth muscle

These tumors represent approximately 3% of all soft tissue sarcomas, with an incidence of less than 1 per 100,000 per year 2, 3.

Clinical Presentation

• Typically presents as a firm, solitary nodule in the skin
• Size usually ranges from 1-3 cm in diameter
• May be associated with pain, pruritus, or paresthesia
• Most common in adults over 50 years, with peak incidence between 60-70 years
• More frequently affects men than women
• Common locations include extremities, trunk, and scalp 3, 4

Prognostic Factors and Risk Assessment

The prognosis varies significantly based on tumor depth:

• Dermal leiomyosarcoma:

  • Better prognosis (5-year overall survival ~98%)
  • Rarely metastasizes
  • Local recurrence rate ~15% with adequate margins

• Subcutaneous leiomyosarcoma:

  • Worse prognosis (5-year overall survival ~88%)
  • Higher metastatic potential (21% metastasis rate)
  • Most common metastatic site is the lungs
  • Local recurrence rate ~22% with adequate margins 5

Diagnostic Approach

• Clinical examination reveals a firm, often painful nodule
• Imaging (ultrasound, CT, MRI) cannot reliably distinguish between benign and malignant smooth muscle tumors 2
• Definitive diagnosis requires histopathological examination:
  • Cellular pleomorphism
  • Increased mitotic activity
  • Necrosis
  • Positive immunohistochemistry for smooth muscle actin 3, 2

Treatment Recommendations

Primary Treatment

Wide surgical excision with negative margins is the cornerstone of treatment for cutaneous leiomyosarcoma. 2, 6

• Margin recommendations:

  • Minimum 1 cm margin for dermal leiomyosarcoma
  • Wider margins (≥2 cm) for subcutaneous leiomyosarcoma 5, 6

• Surgical approaches:

  • Standard wide excision is most common
  • Mohs micrographic surgery has shown good results in selected cases 7

Adjuvant Therapy

• Radiation therapy:

  • Consider for subcutaneous leiomyosarcoma (used in 68% of cases)
  • Less commonly needed for dermal leiomyosarcoma (used in 25% of cases)
  • May be indicated for positive margins or high-grade tumors 5

• Chemotherapy:

  • Limited role in localized disease
  • May be considered for metastatic disease
  • Options include doxorubicin, dacarbazine, trabectedin, pazopanib, and gemcitabine + docetaxel 2

Surveillance and Follow-up

• For dermal leiomyosarcoma:

  • Every 4-6 months for the first 3-5 years
  • Annual follow-up thereafter

• For subcutaneous leiomyosarcoma:

  • Every 3-4 months for the first 2-3 years
  • Twice yearly up to the fifth year
  • Annual follow-up thereafter
  • Include chest imaging to monitor for lung metastases 2

Genetic Considerations

In rare cases, cutaneous leiomyosarcoma may be associated with Hereditary Leiomyomatosis and Renal Cell Cancer (HLRCC) syndrome, caused by germline mutations in the fumarate hydratase (FH) gene. Patients with this syndrome require:

• Annual skin examinations
• Annual renal MRI starting at age 8
• Annual gynecologic examinations (for females) starting at age 20 1, 2

Clinical Pitfalls and Caveats

• Misdiagnosis as a benign lesion is common due to rarity and nonspecific appearance
• Inadequate surgical margins are the main cause of local recurrence
• Subcutaneous involvement significantly worsens prognosis and requires more aggressive management
• Long-term follow-up is essential due to risk of late recurrence or metastasis 3, 4
• Despite claims of radical surgical treatment, recurrence rates remain significant, warranting vigilant surveillance 3