An angiomatoid fibrous histiocytoma over the left pre auricular region in a 13-year-old boy1. Department of Internal Medicine, Oldness and Nephrologic Diseases, Dermatology, University of Bologna, Italy. email@example.com
Annalisa Patrizi MD1, Michela Tabanelli MD1, Georgia Filippi MD1, Carlotta Gurioli MD1, Paolo Nozza MD2, Francesco Savoia MD1, Pietro Dalmonte MD3, Cosimo Misciali MD1
Dermatology Online Journal 16 (5): 4
2. Department of Pathology "G. Gaslini" Institute Children's Hospital, Genova, Italy
3. Cardiovascular Department "G. Gaslini" Institute Children's Hospital, Genova, Italy
A 13-year-old boy presented to us for the evaluation of a slowly growing mass over the left preauricular region. Physical examination showed a nodular swelling, firm on palpation. The patient had no lymphadenopathy. The findings of magnetic resonance imaging (MRI) and vascular MRI led us to suspect a vascular growth. An incisional biopsy was performed and revealed an angiomatoid fibrous histiocytoma (AFH). Angiomatoid fibrous histiocytoma (AFH) is a rare tumor of the soft tissue with fibrohistiocytic and vascular differentiation that shows an intermediate malignancy grade, mainly occurs in patients younger than 20 years of age, and is usually localized on the extremities. Angiomatoid fibrous histiocytoma is considered to be a tumor of intermediate malignancy because of its less aggressive course in contrast to conventional malignant fibrous histiocytoma (MFH). Our case of AFH is peculiar because of its localization in the pre auricular region and because it appeared in a young patient. Surgical excision with maxillo-facial, chest-abdomen, and neck CT and prolonged follow-up is recommended because rare cases of metastasizing AFH have been reported.
|Figure 1. A slowly growing mass over the pre-auricular region of the right ear|
A 13-year-old boy attended our department for evaluation of a slowly growing mass over the left pre auricular region (Figure 1). The patient did not remember any previous episode of trauma and his medical history was not contributory. Physical examination showed a firm, nodular swelling, approximately 2.5 X 2.0 cm in size. The skin over the nodule was violaceous. The patient had no lymphadenopathy. The findings of magnetic resonance imaging (MRI) and vascular MRI led us to suspect a vascular growth. Subsequently, an incisional biopsy was performed for histopathological examination.
The histopathological examination revealed an angiomatoid fibrous histiocytoma.
The biopsy samples consisted of several pieces of tissue, brownish in color. A dermal tumor was seen.
|Figure 2. Nodular dermal neoplasm (x2)|
Microscopically, this rather hypercellular tumor was composed of both round and spindled cells with vesicular nuclei and eosinophilic cytoplasm. The growth was supplied with a network of small vessels; some larger vessels, forming small cystic spaces, were randomly scattered around the tumor (Figures 2, 3a, and 3b).
The mitotic index was 2 per 10 high-power fields. All the tumor cells expressed vimentin; over half of them expressed CD68. CD31, CD34, smooth muscle actin, and muscle-specific actin were not expressed by the tumor cells.
The immunohistochemical staining for desmin and the myogenic transcription factors, as well as those for cytokeratins, were negative. Among the CD68+ histiocytes were some round cells with stubby cytoplasmatic processes. The tumor was evenly sprinkled with T (CD3+) lymphocytes (Figure 3c).
The histopathological features of this lesion of the superficial soft tissue of the head were in keeping with an angiomatoid fibrous histiocytoma (AFH); the nature of the surgical samples, consisting of small pieces of tissue, prevented us from seeing the pseudocapsule, which is a common histological feature. The tumor did not exhibit any typical features of the conventional cutaneous benign fibrous histiocytoma (FH). The biopsy, however, did not contain epidermis or papillary dermis.
Treatment and follow-up
A wide surgical excision of the tumor was performed under general anesthesia. Follow-up involved clinical observation, maxillo-facial MRI, chest-abdomen, and neck CT at one and six months after the surgical excision. During these periods no local recurrence or pathological systemic lesions were observed.
The term angiomatoid fibrous histiocytoma (AFH) was first proposed by the World Health Organization (WHO) in 1994 and then updated in 2006 to define a variant of malignant fibrous histiocytoma (MFH) .
Angiomatoid fibrous histiocytoma, a rare tumor of soft tissue with fibrohistiocytic and vascular differentiation, shows an intermediate malignancy grade and mainly occurs in patients younger than 20 years of age. It is mainly localized on the extremities.
Recently Thway and colleagues demonstrated the cytogenetics of this particular tumor; 2 specific translocations, t(12:16)(q13:p11) and more recently t(12:22)(q13:q12), were described .
The lesions manifest as a slowly growing swelling or as a multinodular or cystic mass located in the subcutis or lower dermis, in some cases associated with pigmentation [3; 4]. Enzinger  and other authors have reported that the tumor is more common on the extremities (85%) rather than on the head and neck region (10%) or on the trunk (5%). In a few cases the lesions are well-circumscribed and freely movable, resembling lymph nodes; often the clinical picture is similar to a hemangioma or hematoma. Pain and tenderness are rarely encountered .
Microscopic examination characteristically reveals three important features occurring in varying proportion: irregular solid masses and nodules of fibroblast and histiocyte-like cells, focal areas of hemorrhage-filled spaces, chronic inflammatory cells, mainly lymphocytes and plasma cells (proliferating fibroblast and histiocyte-like cells have round or elongated vesicular nuclei and a pale eosinophilic cytoplasm) . Hemosiderin could be demonstrated in many cells and may account for the color of some of the tumors [5; 7]. Multifocal hemorrhage is a striking feature that is predominant in many of the cases. The degree of nuclear atypia in the cells of AFH is modest and mitotic features are rare .
In the angiomatoid (vascular) variant there are numerous small branching vessels in a variable collagenous stroma. Focal hypercellularity resembling that seen in the fibrocollagenous type is often present. Hemosiderin is present in about half the cases.
Immunohistochemical workup is important to determine the appropriate diagnosis. Immunoreactivity for alpha-1 anti-chymotrypsin (ACT) and vimentin is present in all lesions and is commonly positive in hystiocytic lesions, although it has been found in a large range of cell types. It is not clear if the cell of origin is a fibroblast or a more primitive cell. Immunohistochemical staining is positive in most cases for lysozyme, MAC387, and CD68.
In one study, Daw et al.  reported their institutional experience in the classification and the incidence in children of MFH and fibrohistiocytic tumors (FH). The most common soft tissue sarcoma during childhood is rhabdomyosarcoma; nevertheless non-rhabdomyosarcomatous soft tissue sarcomas are a well-defined group of tumors that present different morphologic and clinical features. These authors observed 249 pediatric patients (age <14 years) for a 30-year period and noticed that 17 (7%) of these patients had MFH, 10 had FH, and 1 had a plexiform fibrohistiocytic tumor. The median age of patients at the time of the diagnosis was 7.3 years (range 0.3-29.5 years). The most common primary tumor sites were the extremities and a few patients presented with tumors on the head and neck. Metastases to the lung were present in only three patients affected by MFH.
Angiomatoid fibrous histiocytoma is considered to be a tumor of intermediate malignancy because of its less aggressive course in contrast to conventional MFH. The group of tumors classified under the intermediate malignancy grade is characterized by a tendency to local recurrence, associated with an extremely low rate of systemic metastases .
Our case is rare on account of its localization in the pre-auricular region and because it appeared in a young patient.
A wide and aggressive surgical resection with histologically free margins is mandatory to avoid recurrences. Maxillo-facial, chest-abdominal, and neck CT along with prolonged follow-up is recommended because rare cases of metastasizing AFH have been reported.
Our patient has a good prognosis because of the age of development, the size of the tumor, the negative maxillo-facial MRI, chest-abdominal CT, and neck CT scans.
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