Left Facial Mass in an Elderly Man

The patient was a 63-year-old white man who presented with a 1-month history of a left facial mass in the area of the parotid gland. The mass, which had been slowly enlarging, was firm and measured 1.5 cm. It was not associated with pain, pressure, or any change in facial nerve function. Preoperative magnetic resonance imaging confirmed the mass to be in the parotid gland; there were no other masses in the head or neck. The computed tomographic scan of the chest revealed no evidence of disease. Preoperative fine-needle aspiration biopsy of the parotid mass yielded a diagnosis of a malignant neoplasm.Two and one-half years prior to presentation, the patient had a 6 × 4 × 1-mm macular skin lesion located just lateral to the left eyebrow. Shave biopsy of this lesion revealed a dermal proliferation of spindle and pleomorphic cells admixed with large, epithelioid cells (Figure 1). Occasional multinucleated giant tumor cells were also seen. On the basis of this biopsy, the lesion was excised. The lesion recurred 1 year later and was again excised. The skin biopsy and the 2 subsequent surgical excisions had similar histologic appearances.Regarding the current presentation, the patient underwent a superficial parotidectomy, which revealed a 1.5 × 1.1 × 1.0-cm well-circumscribed, encapsulated, and hemorrhagic mass. The tumor appeared to be within an intraparotid lymph node because lymphoid tissue was present at the periphery of the mass (Figure 2). Numerous spindled and large polygonal cells with extensive nuclear pleomorphism were again seen (Figure 3). Tumor giant cells were present and mitotic activity was high. Immunohistochemical evaluation revealed the tumor cells to be positive for CD68 (Figure 4) and vimentin, and negative for cytokeratins (AE1/AE3), smooth-muscle actin, CD45, S100 protein, HMB-45, glial fibrillary acidic protein, and CD31.What is your diagnosis?Atypical fibroxanthoma is a cutaneous tumor of fibroblastic/myofibroblastic origin that typically occurs on sun-exposed skin of the head and neck of adults. Although atypical fibroxanthoma has a “malignant” histologic appearance, it typically follows a benign clinical course. Recurrences are common, but metastasizing atypical fibroxanthoma is rare. We present a case of atypical fibroxanthoma on the left side of the face of an elderly man that subsequently metastasized to an ipsilateral intraparotid lymph node.Atypical fibroxanthoma (AFX) is a cutaneous tumor of fibroblastic/myofibroblastic origin with marked cellular pleomorphism and histiocytic differentiation, but with a typically benign biologic behavior.1 Recurrences are common, but metastasizing AFX is rare.2 As shown in this case, AFX metastasizes primarily to regional lymph nodes.2 Atypical fibroxanthoma typically occurs on sun-exposed skin in elderly individuals, with a male predominance (2:1).1 Most of these lesions arise as rapidly growing nodules and are less than 2 cm in size at the time of biopsy. The head and neck are the most common locations, but lesions on the trunk and limbs have been described, especially in younger patients. In spite of its malignant histologic appearance, AFX is not considered an aggressive neoplasm. In most cases, surgical excision results in complete cure.The tumor is typically located in the dermis and extends upward to the dermoepidermal junction.1 The tumor is usually composed of 3 different cell types, all of which exhibit marked pleomorphism.1 The predominant type is a spindle-shaped cell, often with a plump, prominent, and vesicular nucleus. Intermixed are numerous large, polygonal cells with abundant, often vacuolated, cytoplasm. The third cell type is the multinucleated tumor giant cell. Necrosis is uncommon except near an ulcerated surface. Rare cases of AFX containing osteoid, cartilage, osteoclast-like giant cells, and pigment have been described.1 These features contribute to the overall malignant appearance of AFX.Immunohistochemical evaluation of AFX has revealed consistent staining with vimentin.3 CD68 (57%) and smooth muscle actin (41%) are characteristically expressed as well.4 Recent reports have shown that a high percentage of AFX lesions express procollagen-1 (87%) and CD99 (73%).56 Importantly, cytokeratins and S100 protein have had consistently negative findings, excluding sarcomatoid carcinoma and malignant melanoma from the differential diagnosis of these lesions.3 Of interest, HMB-45 and MART-1 expression within the giant cells of AFX have been documented in a rare case.7Because of the common histologic and immunophenotypic profiles, AFX, superficial malignant fibrous histiocytoma, and deep malignant fibrous histiocytoma have been considered by some authors as a spectrum of biologic behavior within a single pathologic entity.8 Some authors have suggested that the distinction between these entities should be abandoned. The primary contention is that AFX has a good prognosis simply because of its size, dermal location, and lack of metastasis. Malignant fibrous histiocytoma is a similar tumor to AFX histologically, but it has a much worse prognosis. Malignant fibrous histiocytoma has been documented to be aneuploid more frequently than AFX.9 Malignant fibrous histiocytoma expresses LN-2 (CD74) significantly greater than does AFX, suggesting that the acquisition of LN-2 is a marker of progression.10 Ultraviolet light has been thought to play a role in the pathogenesis of AFX because of the common location of AFX on sun-damaged skin.11 Further studies, especially those employing molecular techniques, are warranted regarding the pathogenesis of AFX.In summary, AFX is a lesion with an overall malignant histologic appearance but with a benign clinical course. As this case and other published cases demonstrate, metastasis can occur in AFX.