From the Guidelines
Epithelioid fibrous histiocytoma spindle cell variant with focally involved section edges is a rare dermatological tumor that requires re-excision with wider margins to ensure complete removal and prevent recurrence. This diagnosis indicates that the tumor shows a mixture of epithelioid cells (round cells with abundant cytoplasm) and spindle-shaped cells, with the pathology report noting that the tumor extends to the edges of the surgical specimen in some areas. The involvement of section edges (positive margins) suggests that complete excision may not have been achieved. The management of this condition is crucial, as incomplete removal can lead to local recurrence rates, similar to other spindle cell tumors such as Atypical Fibroxanthoma (AFX)/Pleomorphic Dermal Sarcoma, which may be mistaken clinically or histologically for other spindle cell tumours 1. Key considerations in the management of epithelioid fibrous histiocytoma spindle cell variant include:
- Complete surgical excision with wider margins to prevent recurrence
- Follow-up examinations every 6-12 months for at least 2-3 years to monitor for potential recurrence
- Distinction from other cutaneous neoplasms based on characteristic histological features and immunohistochemical profile, often showing positivity for certain markers. In the context of soft tissue sarcomas, the UK guidelines for management emphasize the importance of securing a diagnosis through preoperative core/punch biopsy, especially for tumors arising at sites where wide excision is not possible 1. Given the potential for local recurrence and the importance of complete excision, re-excision with wider margins is the recommended management approach for epithelioid fibrous histiocytoma spindle cell variant with focally involved section edges.
From the Research
Epithelioid Fibrous Histiocytoma Spindle Cell Variant
- Epithelioid fibrous histiocytoma (EFH) is a rare dermal neoplasm that can exhibit a spindle cell morphology, known as the spindle cell variant of EFH 2.
- This variant can be challenging to diagnose due to its resemblance to other dermal neoplasms, and its distinction from benign fibrous histiocytoma (BFH) may not always be straightforward 3.
- The spindle cell variant of EFH has been found to express anaplastic lymphoma kinase (ALK) protein, which can be a useful diagnostic marker 2, 4.
Histopathological Features
- The spindle cell variant of EFH is characterized by a tumor composed exclusively of spindle cells, without any epithelioid cells 2.
- The tumor cells can exhibit a whorled growth pattern and myxoid-to-collagenous stroma 4.
- Other features that may be present include an epidermal collarette, perivascular hyalinization, amianthoid collagen, and metaplastic ossification 4.
Molecular Genetics
- EFH, including the spindle cell variant, has been found to harbor ALK gene rearrangements, which can be detected using fluorescence in situ hybridization (FISH) or next-generation sequencing-based assays 2, 4, 3.
- The ALK gene rearrangements can involve various fusion partners, including DCTN1, FLNA, SQSTM1, and VCL 2, 4.
- In some cases, alternate receptor tyrosine kinase (RTK) fusions, such as RET and NTRK3, may be present instead of ALK fusions 4.
Diagnostic Considerations
- The diagnosis of EFH, including the spindle cell variant, requires a combination of histopathological and molecular genetic analysis 2, 4, 3.
- Immunohistochemistry for ALK protein can be a useful diagnostic tool, but it should be interpreted in the context of the overall histopathological and molecular genetic findings 2, 4.
- The presence of EMA positivity in some cases of EFH can be a potential diagnostic pitfall, and it is essential to consider the overall immunohistochemical profile and clinicopathologic features when making a diagnosis 5.