Abstract
Aneurysmal fibrous histiocytoma (AFH) is a type of fibrohistiocytic tumour. We present a case of a patient who presented with a skin papule on the thigh region. Histopathological examination following total excision of the lesion revealed an AFH. No sign of recurrence was present 6 months after surgery.
Keywords: dermatology, plastic And reconstructive surgery, skin
Background
Fibrohistiocytic skin tumours are superficially located mesenchymal neoplasms with fibroblastic, myofibroblastic and histiocytic differentiation.1 Fibrous histiocytoma is a type of fibrohistiocytic tumour and has several different variants, including common (dermatofibroma), aneurysmal, haemosiderotic, epithelioid, cellular, lipidised, atrophic and clear cell variants.2 These are most commonly benign. The malignant form of fibrous histiocytoma is rare, and it is a type of sarcoma and can originate from the bone and the soft tissue. Aneurysmal fibrous histiocytoma (AFH) is a rare variant of fibrous histiocytoma.3 It has higher risk of local recurrence compared with dermatofibroma and could histologically be confused with tumour of vascular origin.
Case presentation
A 34-year-old male patient was referred to our clinic with a 7-month history of skin lesion on the right thigh region. Physical examination revealed a brown-blue skin papule with a 5 mm diameter and firm to touch with palpation (figure 1). The lesion was not tender, warm or blanchable with palpation.
Figure 1.
Preoperative photograph of the skin papule.
Differential diagnosis
Dermatofibrosarcoma protuberans, nodular fasciitis, plexiform neurofibroma, melanoma, vascular tumours and fibroblastoma should be included in the differential diagnosis.
Treatment
An incisional biopsy was performed to rule out melanoma and sclerosing blue nevus. Pathological evaluation was compatible with fibrohistiocytic skin tumours. For a definitive diagnosis, total excision of the lesion was performed with a 2 mm margin. The histopathological evaluation was compatible with AFH. Immunohistochemical analysis revealed that S-100 and Melan-A stainings were negative (figure 2). Surgical margins were reported as intact.
Figure 2.
Histopathological images show the presence of irregular, cleft-like spaces without endothelial lining. (A) HE ×40. (B) HE ×100.
Outcome and follow-up
Monthly follow-up was performed after the surgery. There was no sign of recurrence 6 months after the surgery.
Discussion
Fibrous histiocytomas are a benign dermal tumours classified under soft tissue fibrohistiocytic tumours. These can originate from fibroblastic and histiocytic cells. AFH is a rare morphological variant of fibrous histiocytoma. They are most commonly found in the trunk and extremities at sites of trauma. A high risk of local recurrence after inadequate excision with positive tumour margins has been reported.4 Currently there are no specific recommendations available regarding the excision margin in the treatment of AFH. Metastasis of benign-appearing cutaneous fibrous histiocytoma has been reported on very rare incidences.5
The pathogenesis of AFH is explained by vessel proliferation and haemorrhage inside a pre-existing fibrous histiocytoma. Angiomatoid malignant fibrous histiocytoma (AFHM) should be differentiated from AFH. Clinically AFHM is more frequently seen in children and could be located in the subcutaneous tissue as opposed to AFH.6 The clinical appearance of the lesion can be confused with malignant melanoma or haemangioma. The pathological features could also be confusing, and it could be confused with vascular tumours such as angiosarcoma and Kaposi sarcoma (KS).4 7 KS is usually found in the lower extremities of older individuals. Vascular spaces found in KS are CD34-positive, which indicates that they are lined with the endothelial cells as opposed to AFH. Angiosarcoma similarly has CD34-positive endothelial linings which are atypical and mitotically active. Immunohistochemical staining can be performed to differentiate AFH from other similar-appearing lesions. This can be done with the S-100 stain for sarcoma, neurofibroma and melanoma. Melan-A, which is less sensitive than S-100, but is more specific, can also be used for melanoma.8
Learning points.
Aneurysmal fibrous histiocytoma is a type of fibrohistiocytic tumours.
The clinical appearance of the lesion could be confused with melanoma.
There is a high risk of local recurrence in case of inadequate margin clearance.
Footnotes
Contributors: MS wrote the manuscript and performed the surgery. CL performed the pathological analysis. SKY and EKA contributed to the revision of the manuscript.
Funding: The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests: None declared.
Patient consent: Obtained.
Provenance and peer review: Not commissioned; externally peer reviewed.
References
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