ABSTRACT:
Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue neoplasm of intermediate biologic potential that occurs mostly in extremities and is often misdiagnosed initially, because of its clinical and radiological similarity to other diseases.1-4 .Clinically it is very difficult to differentiate it from other tumors like angiosarcoma or a simple organised hematoma 2 .Similarly, Histopathology is not always revealing. Surgery is the mainstay of management and can effectively control local recurrence and metastasis if planned beforehand. Herein ,we describe a case report of a 55 year-old female who presented with a swelling in the popliteal region which on clinical and radiological evaluation revealed a popliteal cyst and was managed by an unplanned excisional biopsy. We present this case to emphasize to clinicians that the chances of improper management of such tumors with unplanned excision are high , if such differentials are not kept in mind preoperatively.
INTRODUCTION:Angiomatoid fibrous Histiocytoma(AFH) is a rare soft tissue tumor with intermediate biologic potential that is commonly found in the extremities of children , adolescents and young adults in deep dermis and subcutaneous plane1,2,4,5 .It was initially described as angiomatoid malignant fibrous histiocytoma by Enzinger1 ,but it is no longer regarded as malignant because of its benign appearance and favourable prognosis2,5 .Because of its indolent clinical presentation and radiological features , it is often misdiagnosed for a benign condition such as a hematoma, hemangioma or simple cysts leading to inappropriate treatments such as unplanned excision5. Although the prognosis of AFH is not poor , it recurs in up to 15 % of cases and metastasizes in fewer than 1 % of cases2 .So, keeping AFH as a differential in cases with soft tissue masses can guide us to do an extended resection of the tumor with wide margins and minimise the chances of recurrence.
CASE PRESENTATION :
A 45 year old female presented to us with a history of  right knee pain for 6 months and swelling in the posterior aspect of the knee for 1 year, which has been gradually increasing in size. The patient had difficulty squatting and sitting cross-legged . There were no constitutional symptoms. Past medical, surgical and family history were not significant. On examination, there were two soft cystic , fluctuant, non-tender swelling , each around 7*5 cm arising from the posteromedial aspect of the right knee lying longitudinally in craniocaudal fashion (Figure 1).There were no skin changes .USG findings revealed a fluid filled , well circumscribed, dumbbell  shaped  mass   with  2 cysts, each of sizes  around 6*5*3 cm communicating with each other arising from the posteromedial knee with a neck at its deepest extent, extending into the joint space between the semimembranosus and medial head of gastrocnemius suggestive of popliteal cyst. The patient underwent en bloc surgical excision(Figure 2,3,4) .On histopathological examination, the lesion demonstrated  characteristic features of Angiomatoid Fibrous Histiocytoma including multinodular growth of myoid spindled or histiocytoid cells with a distinctive syncytial appearance, pseudo-angiomatous spaces filled with blood and surrounded by tumour cells , a thick fibrous pseudo capsule with peritumoral lymphoplasmacytic cuffing with occasional germinal center formation, areas of prominent hemosiderin deposition and foam cells within the tumour cells (Figure 5,6). Immunohistochemistry for supporting the diagnosis was planned  but due to resource constraints, we could not manage the same.