In a young adult with a rapidly enlarging painless subcutaneous nodule on the upper extremity whose biopsy shows a spindle‑cell neoplasm favoring nodular fasciitis, what is the most appropriate initial management?

Management of Nodular Fasciitis

For a young adult with a rapidly enlarging painless subcutaneous nodule on the upper extremity with biopsy-confirmed nodular fasciitis, observation without surgical intervention is the most appropriate initial management, as this benign lesion characteristically undergoes spontaneous resolution within 3-8 weeks. 1

Understanding Nodular Fasciitis

Nodular fasciitis is a benign, self-limited myofibroblastic proliferative lesion that is frequently misdiagnosed as sarcoma due to its rapid growth, high cellularity, and increased mitotic activity 2, 3. Despite these concerning features, it is the most common pseudosarcoma of soft tissues and has an excellent prognosis 2.

Initial Management Strategy: Active Surveillance

The primary management approach should be nonsurgical observation with close monitoring. 1

Expected Timeline for Resolution

• Spontaneous resolution typically occurs within 3-8 weeks (median 4 weeks) after diagnosis 1
• In documented cases, complete resolution has been observed in patients followed for up to 11 months 1
• The lesion will gradually decrease in size and eventually disappear without intervention 4

Monitoring Protocol

• Clinical examination should be performed at regular intervals to document progressive size reduction 1
• If the lesion does not show signs of resolution within 6-8 weeks, surgical excision should then be considered 1
• Any increase in size or change in clinical characteristics warrants immediate reassessment 4

When Surgery Becomes Necessary

Surgical excision should be reserved for cases where:

• The lesion fails to regress after 6-8 weeks of observation 1
• There is diagnostic uncertainty and malignancy cannot be excluded pathologically 4
• The lesion increases in size during the observation period 4

If surgery is performed, local excision is the treatment of choice, as recurrence is exceedingly rare 2, 3.

Critical Diagnostic Considerations

Distinguishing from Malignancy

The key challenge is differentiating nodular fasciitis from true sarcomas, particularly malignant peripheral nerve sheath tumor (MPNST) or other spindle cell malignancies 4, 5. This distinction requires:

• Correlation of pathological findings with clinical features 4
• Recognition that typical nodular fasciitis lesions are less than 5 cm and enlarge rapidly over days to weeks 1
• Awareness that the upper extremities are a common location in adults 3

Pathological Features Supporting Nodular Fasciitis

• Benign-appearing spindle cells (singly and in groups) 1
• Presence of collagen and myxoid material 1
• Proliferation of fibroblasts and myofibroblasts in subcutaneous tissues 3

Common Pitfalls to Avoid

The most critical error is performing aggressive surgical treatment based solely on the histologic appearance of high cellularity and mitotic activity without considering the clinical context 2, 3. This benign lesion does not require wide excision or the extensive surgical approaches used for true sarcomas 2.

Another pitfall is failing to recognize potential recurrence: While exceedingly rare, recurrence can occur even years after initial resolution, and such cases require careful evaluation to exclude malignancy 4.

Special Circumstance: Recurrent Lesions

If a lesion recurs at the same site after initial spontaneous resolution, particularly years later, the possibility of malignancy must be reconsidered 4. In such cases:

• Excisional biopsy with complete histopathological examination is warranted 4
• If pathological findings suggest possible malignancy (such as low-grade MPNST), wide resection should be performed 4
• The patient should be managed considering the possibility of malignancy when diagnostic uncertainty persists 4