Introduction
Atypical fibroxanthoma (AFX) is a low-grade superficial sarcoma that typically develops on chronically sun-damaged skin, particularly in the head and neck region, of elderly individuals.1 Clinically, AFX typically presents as a rapidly growing erythematous or violaceous papule or nodule, often with ulceration.1,2 Histopathologically, it is characterized by a dermal proliferation of pleomorphic spindle and epithelioid cells with frequent atypical mitoses and tight juxtaposition to an atrophic or ulcerated epidermis.2
AFX remains a diagnosis of exclusion, lacking a specific immunohistochemical marker and requiring distinction from spindle cell squamous cell carcinoma, melanoma, leiomyosarcoma, and angiosarcoma.2 Numerous histologic variants have been described, including osteoclastic giant cell-rich forms, which are rare and might pose diagnostic difficulty.3,4
In addition to histologic heterogeneity, AFX may exhibit atypical clinical morphologies.5 Rare cases have mimicked benign vascular lesions such as hemangiomas or venous lakes, increasing the risk of misdiagnosis.5,6
Herein, we report 2 cases of AFX with osteoclastic giant cells that clinically presented as vascular lesions. This combination represents a rare and diagnostically challenging clinicopathologic variant with potential for confusion with vascular neoplasms, including angiosarcoma.
Case reports
Case 1
A 77-year-old man presented with a newly developed dark red-purple, well-circumscribed papule on the upper portion on the back of the right arm (Fig 1, A). The lesion appeared clinically vascular, favoring a benign vascular proliferation.
Fig 1.
A, Dark red-purple, well-circumscribed papule on the upper portion on the back of the right arm with a vascular appearance. B, Dermal proliferation of pleomorphic spindle cells with atypical mitoses, hemorrhage, and admixed osteoclastic giant cells. C, Immunostaining highlighting multinucleated osteoclastic giant cells. (B, Hematoxylin-eosin stain; C, CD68+ immunostain; original magnifications: B, ×10; C, ×10).
Shave biopsy revealed a dermal-based pleomorphic spindle cell neoplasm with numerous atypical mitoses and admixed osteoclastic giant cells on hematoxylin-eosin stain (Fig 1, B). Immunohistochemistry demonstrated positivity for CD10, CD68, and c-MYC and negativity for Melan-A, CK5/6, smooth muscle actin, CD31, CD34, and ERG. MYC is often used to support angiosarcoma; however, negative CD31, CD34, and ERG stains suggest against this diagnosis.7 Recent studies suggest that CD10 can be a useful positive immunomarker for AFX because there are few differential diagnoses in the skin with CD10 positivity besides spindle cell squamous cell carcinoma.5,8 Independent dermatopathology review confirmed AFX with osteoclastic giant cells, with CD68 highlighting the multinucleated giant cells (Fig 1, C).
The patient underwent staged excision with complete margin evaluation. No recurrence was observed at 3-month follow-up. However, the relatively short follow-up period is a limitation because most AFX recurrences occur within 1 to 2 years.
Case 2
A 77-year-old man presented with a slowly enlarging dark red-purple papule on the left antitragus (Fig 2, A). The lesion was clinically suggestive of a benign vascular tumor.
Fig 2.
A, Dark red-purple papule on the left antitragus clinically suggestive of a vascular lesion. B, Pleomorphic dermal spindle cell neoplasm with hemorrhage and osteoclastic giant cells. (Hematoxylin-eosin stain; original magnification: ×20).
Histopathologic examination demonstrated a pleomorphic dermal spindle cell neoplasm with hemorrhage and numerous osteoclastic giant cells (Fig 2, B). Initial immunostaining showed CD68 positivity and focal CD31 staining, raising concern for angiosarcoma or even a histiocytic/myeloid proliferation. The case was referred for expert consultation for further classification. Repeat staining for CD31, CD34, and ERG was negative, excluding vascular malignancy, and the lesion was classified as an atypical intradermal spindle cell neoplasm most consistent with AFX.
The patient underwent staged excision with complete margin control. No recurrence was observed at the 2-year follow-up.
Discussion
AFX is a diagnostically challenging tumor due to its histologic variability and lack of specific immunohistochemical markers.2,5 While most cases present as erythematous or ulcerated nodules, atypical clinical presentations, including vascular-appearing lesions, have been reported.5,6 These lesions may mimic benign vascular proliferations, potentially delaying biopsy and diagnosis.
The osteoclastic giant cell variant of AFX is rare, with fewer than 20 cases reported.3,4 These CD68+-multinucleated cells are considered reactive rather than neoplastic but may raise concern for more aggressive entities such as pleomorphic dermal sarcoma or angiosarcoma.4 Pleomorphic dermal sarcoma has deeper subcutaneous invasion, necrosis, lymphovascular invasion, or even perineural invasion, with a higher recurrence rate and metastatic rate than AFX.8 During staged excision of both lesions, the aforementioned histologic findings were absent, precluding a diagnosis of pleomorphic dermal sarcoma.
The combination of a vascular clinical appearance and osteoclastic giant cells, as seen in our cases, represents a particularly uncommon presentation that may further confound diagnosis. Prior reports have described AFX with hemorrhage, pseudoangiomatous features, or vascular mimicry, underscoring the importance of histopathologic evaluation in suspicious vascular-appearing lesions in sun-exposed skin.5,6
Immunohistochemistry is essential in excluding mimickers. Although vascular markers such as CD31 may show nonspecific or focal staining, true vascular tumors are typically confirmed by diffuse positivity for CD31, CD34, and ERG.7 Careful interpretation in conjunction with morphology is critical.
AFX generally carries a favorable prognosis with low metastatic potential (metastasis rate, 0.59%) but a risk of local recurrence (local recurrence rate, 4.73%).9 Mohs micrographic surgery or staged excision with complete margin assessment is associated with lower recurrence rates.10
This report highlights a rare clinicopathologic variant of AFX characterized by both vascular clinical mimicry and osteoclastic giant cells. Recognition of this presentation is important to avoid misdiagnosis as a benign vascular lesion or angiosarcoma and to ensure appropriate management.
Conflicts of interest
None disclosed.
Footnotes
Funding sources: Supported (in whole or in part) by HCA Healthcare and/or an HCA Healthcare affiliated entity. The views expressed in these publications represent those of the authors and do not necessarily represent the official views of HCA Healthcare or any of its affiliated entities.
Patient consent: The authors attest that they have obtained written consent from patient/s, their legal guardian/s or person/s with legal authority, for their photographs and medical information to be published in print and online and with the understanding that this information may be publicly available. Patient consent forms were not provided to the journal but are retained by the authors to be made available upon request.
IRB approval status: Not applicable.
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