Spindle Cell Atypical Fibroxanthoma: Myofibroblastic Differentiation Represents a Diagnostic Pitfall in This Variant of AFX

Keloidal atypical fibroxanthoma of the scalp

Atypical fibroxanthoma (AFX) is a rare low-grade sarcoma that occurs mainly in the elderly and may recur locally. There are multiple variants including keloidal AFX (KAF). KAF is characterised by a proliferation of atypical spindled and epithelioid cells admixed with bizarre pleomorphic cells. These cells intersect among broad bands of keloidal collagen. AFX is a diagnosis of exclusion so a broad panel of immunohistochemical staining should be applied to rule out other differentials (squamous cell carcinoma (SCC), melanoma, leiomyosarcoma, etc). There is added difficulty with the diagnosis of KAF as it may mimic multiple keloidal lesions, including exuberant scarring, as in this case. p53 immunohistochemistry staining can be useful in highlighting the presence of tumour cells. Additionally, next generation sequencing can detect genetic mutations identified in clonal proliferations consistent with tumour formation. KAF is easily overlooked and it should be included in the differential diagnosis for keloidal lesions showing even mild atypia.

Pleomorphic Dermal Sarcoma With Metastasis to the Lung: A Case Report

ABSTRACT

Atypical fibroxanthoma and pleomorphic dermal sarcoma (PDS) are dermal malignant mesenchymal tumors that lie at the ends of the same disease spectrum. Clinically indistinguishable from atypical fibroxanthoma, PDS has a more aggressive course with significantly higher rate of local recurrence and metastases. Histological findings that favor a PDS include subcutaneous invasion, tumor necrosis, lymphovascular invasion, and/or perineural infiltration. Herein, we report a case of PDS with metastasis to the lung. Our report highlights the risk of local recurrence and metastatic spread in this cutaneous tumor and the importance of distinguishing this entity from its less aggressive counterpart.

Relation Between Atypical Fibroxanthoma and Pleomorphic Dermal Sarcoma: Histopathologic Features and Review of the Literature

The relation between atypical fibroxanthoma and pleomorphic dermal sarcoma has led to confusion and debate in the literature. Both tumors present on sun-exposed skin, typically on the head and neck, in patients of advanced age. Both are comprised of a variable mix of histiocytoid, spindle, epithelioid, and/or giant multinucleated cells with pleomorphic nuclei. No immunohistochemical diagnostic techniques have emerged to distinguish these tumors. Diagnosis is by exclusion. Histologically, atypical fibroxanthoma is seen as a well-circumscribed dermal nodule but there will be no evidence of extensive subcutaneous invasion, tumor necrosis, or lymphovascular or perineural invasion. Therefore, if any of the aforementioned features is present, the diagnosis would be pleomorphic dermal sarcoma. This narrative review of the literature aims to identify the distinguishing and overlapping histopathologic features of these 2 tumors as they have been described in case series.

Could cathepsin-k be a driver of the myofibroblastic differentiation observed in dermatofibroma, atypical fibroxanthoma and pleomorphic dermal sarcoma?

Dermatofibroma (BFH), atypical fibroxanthoma (AFX) and dermal pleomorphic sarcoma (DPS) are skin-based soft-tissue neoplasms of uncertain lineage. They are classified as "fibrohistiocytic" neoplasms, even if the World Health Organization stated that this term connotes a polymorphic group of lesions that histologically resemble fibroblasts and histiocytes. It is well-known that this group of lesions shows a "fibro-histiocytic-dendritic" and/or a "myofibroblastic" phenotype, even within the same lesion. We studied the expression of cathepsin-k in 34 cases (25 BFH, 5 AFX, 4 DPS) with a broad panel of antibodies. 20 cases (5 dermatofibrosarcoma protuberans, 5 melanomas, 5 basal cell carcinomas, 5 squamous cell carcinomas) were chosen as controls. Although our results need to be validated, they support a myofibroblastic and/or partial myofibroblastic ("proto-myofibroblastic") phenotype and the lineage-plasticity of these neoplasms, highlighting the potential role of cathepsin-k in myofibroblastic trans-differentiation. Cathepsin-k proved to be an additional immunoistochemical marker potentially useful in the diagnostic algorithm.

Primary leiomyosarcoma of the skin: a comprehensive review on diagnosis and treatment

Sarcomas are a heterogeneous group of mesenchymal tumors which can affect bone and soft tissue. Leiomyosarcoma (LMS) is a rare subtype localized to the skin or subcutaneous tissue. Due to the heterogeneity of sarcomas, reviews and guidelines with an in-depth focus specifically on primary LMS of the skin are sparse. This article is intended to provide an up to date and systematic overview on diagnosis, treatment, and surveillance of this rare entity to provide a framework for decision making and management for dermato-oncologists. We discuss novel treatment options for advanced disease such as targeted therapy with kinase inhibitors and immune checkpoint blockade which may improve the prognosis even in advanced stages of LMS.

Aberrant tyrosinase expression in an atypical fibroxanthoma: A case report

Atypical fibroxanthoma (AFX) is a histologic mimicker of a variety of spindle cell neoplasms, and careful microscopic and immunohistochemical evaluation is critical in establishing the correct diagnosis. Here we report the histologic and immunohistochemical work up of a 1 cm nodule involving the left dorsal hand of a 66-year-old patient. Light microscopy revealed fascicles of spindled and pleomorphic cells within the dermis showing increased mitotic activity occurring in the background of sun-damaged skin. There were numerous multinucleated cells with hyperchromatic nuclei and ample finely vacuolated or foamy cytoplasms. There was strong and diffuse CD10 and patchy CD68 expression among the spindled cells and multinucleated cells. The neoplastic cells did not show immunoreactivity against S100, p75-NGFR, HMB-45 or a panel of keratinocytic, vascular and smooth muscle markers. Tyrosinase and Melan-A were not expressed within the spindle cell component of this neoplasm; however, there was tyrosinase expression among numerous multinucleated giant cells. Melan-A expression was also observed among rare multinucleated giant cells. Tyrosinase expression has not previously been reported in AFX.

Case of Pleomorphic Dermal Sarcoma of the Eyelid Treated with Micrographic Surgery and Secondary Intention Healing

Pleomorphic dermal sarcoma (PDS) is a rare mesenchymal neoplasm sharing histopathological features with atypical fibroxanthoma (AFX), but has additional features of deep invasion of the superficial subcutis, tumor necrosis and vascular/perineural invasion. It is not well documented in the literature because of its rarity, and its clinical course has been debated due to the lack of homogenous criteria. We describe here the case of a 91-year-old female with a 6-month history of a solitary, asymptomatic, well-defined, 3.4-cm-sized, reddish, hard, protruding mass on the lateral aspect of the right upper eyelid. On the basis of initial punch biopsy results, storiform cellular infiltrate of pleomorphic spindle and polygonal cells with frequent atypical mitoses, the lesion was identified as AFX. Following the initial biopsy, micrographic surgery was performed and a tumor-free margin was confirmed. Considering the conservation of the periocular function and the advanced age of the patient, we planned secondary intention healing rather than primary suturing. After surgery, skeletal muscle infiltration was found and the diagnosis was revised to PDS by a pathologist based on the currently accepted criteria for PDS. There has been no evidence of recurrence or periocular functional defects during a 2-year follow-up without adjuvant therapy. Although the PDS is highly malignant, complete excision under micrographic surgery can prevent recurrence without adjuvant therapy. Also, the secondary intention healing is an effective method for closure of large defects on the face.