Recurrent Angiomatoid Fibrous Histiocytoma of thigh in a middle aged female: A case report

Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue tumor of intermediate malignant potential seen predominantly in children and young adults. We here report a case of recurrent AFH in right medial thigh of a 46 year old female which recurred locally within 13 months of wide local excision of the mass. The lesion may mimic hematoma, soft tissue hemangioma, nodular malignant melanoma or any cutaneous and skin adnexal tumor clinically as well as radiologically. Hence it is imperative to consider this lesion in the differential diagnosis of a soft tissue tumor in spite of elderly age.


Introduction
Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue tumor of intermediate malignant potential, which accounts for approximately 0.3% of soft-tissue neoplasms [1,2]. It is predominantly seen in the deep dermis and subcutis of the extremities of children and young adults. [3,4]. Apart from extremity, it has been also reported to occur at various sites like hard palate, mediastinum, vulva, retroperitoneum, ovary, and lung [5]. Majority of AFH are slow growing and painless lesions [6] while systemic symptoms such as pallor, fever and weight loss are rarely encountered. . Herein, we present the case of a 46 year old female with a local recurrence of an AFH over the right medial thigh.

Case Report
A 46 year old female presented to the outpatient department in our institute with painless slow growing lump over the medial aspect of the right thigh for the past 5 years with increase in size since 6 months. Clinical examination revealed a mass measuring 3x2cm with overlying purple brown to dark skin surface. The mass was well circumscribed with uneven consistency varying soft to firm. General physical examination was within normal limit. An excision wedge biopsy was performed. On histomorphology, a diagnosis of Angiomatoid Fibrous Histiocytoma was given. Comment on surgical margin of the wedge biopsy was not possible. However, the patient was lost to follow-up. After 13 months, she again presented to our institute with recurrence of similar lesion at same site along with ulceration and bleeding from the overlying skin. A wide local excision of the right thigh mass was performed. Grossly, it measured 6x6x3cm, overlying ulcerated skin measured 6.5x3cm. Cut section of the specimen showed a fairly circumscribed, soft to firm, brownish tumor nodule with area of hemorrhage Based on classical morphology and immunohistchemistry, a diagnosis of AFH was made. Postoperatively, she has done well and after thirteen months since her re-excision, the patient shows no evidence of recurrence to till date and is on regular follow up every 6 month.

Discussion
The term -Angiomatoid Malignant Fibrous Histiocytoma‖ first described by Enzinger in 1979 [3]. Initially, A MFH was described as a variant of malignant fibrous histiocytoma; Because of its benign microscopic appearance , relatively rarity of metastasis [7] and overall excellent clinical course, in World Health Organization (WHO) 2002 classification, it was removed from the malignant fibrous histiocytoma subtype of sarcoma and was placed under the category of tumors of uncertain differentiation as angiomatoid fibrous histiocytoma [6]. AFH is mostly seen in the first 2 decades of life, although the age distribution is wide, ranging from infant [8] to eight decade [2]. No sex predilection is noted. Majority of case occur in extremity followed by trunk and head and neck. However, occurrence of AFH in non somatic soft tissue sites such as the lung, mediastinum, vulva, retroperitoneum, ovary, pulmonary artery, kidney, and brain [9]. Omentum [10], ovary, vulva, and bone [11] have been documented in the literature. Our index case was seen in 40 years woman with a recurrent thigh mass measuring 6 cm in maximum dimension. Microscopically, it is characterized by varying proportions of spindled or histiocytoid cells, arranged in a nodular pattern, pseudovascular spaces and prominent lymphoplasmacytic rim [12,13].
However, various morphology of AFH has been documented in the literature. Chen et al reported clear cells, rhabdomyoblast-like cells, pulmonary edema like pattern and myxoid stroma in some AFH cases [5]. Bohman et al have reported perineurioma-like pattern, moderate pleomorphism, significant areas of sclerosis, eosinophils in the stroma [12,13] [12,16] while consistently negative for S100 protein, CD34, CD35, CD21 and Cytokeratin. Our case shows immunopositivity for desmin, EMA and CD68. Cytogenetically AFH is associated with 3 characteristic translocations: t(2:22)(q33:q12), most common, 90% of cases [2], t(12:22)-(q13:q12) and t(12:16)(q13:p11). In our index case cytogenetics studies were not performed as morphology was classical. As AFH have no any distinct clinical or radiological findings, with various morphological pattern and lacks specific immunophenotypic markers, making this diagnosis can be very challenging. . The differential diagnosis of AFH includes Granulomatous inflammation (lacks vascular space), Aneurysmal benign fibrous histiocytoma(heterogeneous cell population than AFH , lacks a surrounding lymphoplasmacytic infiltrate, and is desmin negative) Spindle cell hemangioma(occurs in the dermis and subcutis of extremities and has cavernous vascular spaces but is poorly circumscribed, with true vascular spaces lined by attenuated endothelial cells ) Inflammatory myofibroblastic tumor (myofibroblasts with distinct cell borders and eosinophilic cytoplasm, vesicular nuclei with distinct nucleoli, inflammatory cells intimately intermingled with the neoplastic cells without forming a peritumoral rim. Positive for actin, desmin, and ALK), Nodular Kaposi sarcoma (dermal and circumscribed with bland cytology and contains slitlike blood-filled spaces rather than the cystic ones seen in AFH, express CD34 and human herpesvirus 8). Other rare differentials are Follicular dendritic cell tumor, Ewing sarcoma, Rhabdomyosarcoma, Malignant extra renal rhabdoid and metastatic tumor deposits.
Chow et al reported that the majority of patients are disease free after wide local excision [17]. Fanburg et al reported a 1% frequency of metastasis in their series [1]. In other studies up to 23% of patients may develop recurrence and 8.7% develop metastasis within 24 months post excision [4,18] Due to metastatic potential, AFH has been classified in intermediate malignant potential. Costa et al [19] reported that recurrent AFH can be successfully managed with local radiation, which is an important consideration for our patient.
In conclusion, AFH though rare tumor should be kept in mind in differentials of recurrent soft tissue lesions even in the middle age. It should be managed with appropriate surgical excision to obtain negative surgical margins and patient should be kept on close follow up. Local radiation therapy may be helpful in managing the recurrence.