Atypical Fibroxanthoma: A Histological and Immunohistochemical Review of 171 Cases

Orbital invasion of a conjunctival atypical fibroxanthoma in a patient with systemic diffuse large B-cell lymphoma

An 88-year-old male patient presented with a large mass on the left lateral bulbar conjunctiva. The tumor appeared two months after the resection of a conjunctival atypical fibroxanthoma (AFX) performed by a cornea specialist. Magnetic resonance imaging of the orbits showed deep orbital invasion along the lateral rectus muscle. The mass and the entire conjunctival sac were totally excised with lid-sparing orbital exenteration. Histopathological analysis confirmed that the mass was an extension of the AFX. Two weeks after surgery, large B-cell lymphoma was diagnosed in the oropharynx. Chemotherapy was initiated, and after seven months of follow-up, there was no recurrence of the AFX. The authors believe that this is the first report of orbital invasion by AFX.

Is Primary Poorly Differentiated Sarcomatoid Malignancy of the Parotid Gland Sarcomatoid Undifferentiated/Dedifferentiated Melanoma? Report of Three Unusual Cases Diagnosed by Fine-Needle Aspiration Combined with Histological, Immunohistochemical, and Molecular Analyses

INTRODUCTION

Poorly differentiated primary sarcomatoid parotid malignancies are extremely rare. These tumors have not been consistently studied by morphology, immunohistochemistry, or molecular techniques.

CASE PRESENTATION

We report three unusual cases of parotid gland poorly-differentiated sarcomatoid malignancy investigated by fine-needle aspiration and studied histologically, by immunohistochemistry and molecular investigations. Aspirates showed poorly specific polymorphous sarcomatoid malignancy in all cases. Histologically, all cases were polymorphous high-grade malignancies, and additionally, one case showed epithelial structures and was finally classified as salivary carcinosarcoma. Immunohistochemistry showed classical melanocytic markers negativity but positivity for PRAME, CD10, and WT1 in all three tumors and for CD56 in two tumors, which can potentially be supportive of melanocytic origin. Although not entirely specific, molecular characterization also suggested the melanocytic lineage of these tumors.

CONCLUSION

Although rare, primary malignant melanoma of salivary gland was already described, but undifferentiated/dedifferentiated amelanotic forms are unknown in this localization up today. Further case reports of similar presentations are required to confirm the unequivocal primary origin of these obscure neoplasms in the parotid gland.

Dedifferentiated and undifferentiated melanomas: a practical approach to a challenging diagnosis

Dedifferentiation, defined as the loss of cellular features of terminal differentiation resulting in a more primitive, unspecialized phenotype, is a rare phenomenon in melanoma and more commonly observed in the metastatic setting than in primary melanomas. The diagnosis of dedifferentiated melanoma poses a significant challenge, and the tumors need to be carefully sampled and worked up to identify any residual morphologic, immunohistochemical, or molecular evidence of their melanocytic lineage. This article reviews our current knowledge of the clinical, histopathological, immunohistochemical, and molecular features of these rare tumors and provides a practical diagnostic approach and discussion of the relevant differential diagnoses and associated diagnostic pitfalls.

Cutaneous Atypical Fibroxanthoma With Osteoclast-Like Giant Cell: A Rare but Diagnostic Pitfall

BACKGROUND

Atypical fibroxanthoma (AFX) is a dermal-based, low-grade neoplasm with no specific lineage of differentiation. The occurrence of AFX with osteoclast-like giant cells is exceptionally rare. Less than 20 cases have been reported in the literature.

CASE PRESENTATION

A 77-year-old man with a medical history of multiple basal and squamous cell carcinomas of the skin, presented with a progressively growing erythematous nodule on the sun-damaged right central parietal scalp. A shave biopsy showed a dermal spindle cell proliferation accompanied by numerous osteoclast-like multinucleated giant cells and predominant atypical mitotic figures. The immunohistochemical staining showed a diffuse positive staining for CD68 and SMA, patchy staining for CD10, and negative staining for SOX-10, pan-cytokeratin, CK5/6, S100, CD34, and desmin. The tumor was completely excised with negative margins. A subsequent follow-up over a period of 13 months showed no recurrence.

CONCLUSION

Distinguishing AFX with osteoclast-like giant cells from both malignant and benign skin lesions with osteoclast-like giant cells is crucial. Although AFX tumors display worrisome malignant histologic features, most cases have a favorable prognosis with a local recurrence rate below 5% and exceedingly rare metastasis.

Fine needle aspiration cytopathology of pleomorphic dermal sarcoma

INTRODUCTION

Pleomorphic dermal sarcoma (PDS) is an uncommon cutaneous mesenchymal neoplasm. It is cytomorphologically identical to atypical fibroxanthoma (AFX), but differs due to its invasion beyond the dermis. We undertook an examination of our experience with fine needle aspiration (FNA) biopsy cytology of PDS.

MATERIALS AND METHODS

Our cytopathology files were searched for examples of PDS with concomitant histopathological verification. FNA biopsy smears and cell collection were performed using standard techniques.

RESULTS

Seven cases of PDS were retrieved from four different patients (M:F, 1:1; age range: 63-88 years; mean age = 78 years). All patients (57%) presented with a primary tumour with one having an FNA biopsy of two local recurrences and a single distant metastasis. Five aspirates were from the extremities and two from the head/neck. Tumours ranged from 1.0 to 3.5 cm (mean, 2.2 cm). Specific cytological diagnoses were pleomorphic spindle/epithelioid sarcoma (3 cases), PDS (2), AFX (1), and atypical myofibroblastic lesion, query nodular fasciitis (1). Immunohistochemical (IHC) staining from FNA-generated cell blocks in two cases showed non-specific staining with vimentin in both cases; positive CD10, CD68, and INI-1 staining in one case; and smooth muscle actin expression in the other. Multiple negative stains were performed in both of these cases to exclude malignant melanoma, carcinoma, and specific forms of sarcoma. Cytopathology consisted of a mixture of spindle, epithelioid, and bizarre pleomorphic cells.

CONCLUSION

Coupled with ancillary IHC stains, FNA biopsy can help recognise PDS as a sarcomatous cutaneous neoplasm, but is unable to distinguish PDS from AFX.

The many faces of Atypical fibroxanthoma

Atypical fibroxanthoma (AFX) is an uncommon, primary dermal neoplasm of uncertain histogenesis, typically originating in the sun-damage skin of the head and neck of the elderly. Since first description in 1958, ∼3000 cases have been reported in the literature. However, the disease is underreported as the neoplasm is considered a standard diagnosis in the last decades. On the other hand, many earlier reports likely have included non-AFX mimics or aggressive pleomorphic dermal sarcomas. In contrast to its alarming high-grade histology, AFX behaves indolently with rare recurrences/ metastatic rate of <2%. The overall 10- and 20-year disease-specific survival rates are ∼ 100% and 98%, respectively. Histologically, AFX displays undifferentiated pleomorphic spindle cell morphology akin to undifferentiated pleomorphic sarcoma (UPS), a feature that was the basis of the abandoned historical terminology "MFH of skin". However, in contrast to other undifferentiated sarcomatoid neoplasms, AFX is notorious for its highly variable histology with a plethora of patterns, underlining a wide differential diagnosis. Notably, spindle cell, keloid-like, pleomorphic, epithelioid, rhabdoid, clear cell, foamy cell, granular cell, bizarre cell, pseudoangiomatous, inflammatory, osteoclast-rich, and many others have been recognized with varying frequencies. Immunohistochemically, AFX is characterized by nonspecific profile with block-type expression of CD10 and aberrant p53 pattern and lack of pankeratin and other lineage-specific epithelial, mesenchymal, melanocytic and hematolymphoid markers. Sarcomatoid melanoma, spindle cell carcinoma and cutaneous anaplastic large cell lymphoma are major considerations. Distinction of AFX from pleomorphic dermal sarcoma (PDS) is arbitrary and is based on presence of ≥ 1 of four unfavorable histological features: more than minimal subcutaneous involvement, coagulative necrosis, lymphovascular invasion and perineurial invasion.

Degree of Actinic Elastosis Is a Surrogate of Exposure to Chronic Ultraviolet Radiation and Correlates More Strongly with Cutaneous Squamous Cell Carcinoma than Basal Cell Carcinoma

(1) Background: Keratinocyte cancer (KC) is associated with exposure to ultraviolet (UV) radiation. However, data are controversial as to whether chronic UV exposure or high intermittent UV exposure are key drivers of carcinogenesis in cutaneous squamous cell carcinoma (cSCC) and basal cell carcinoma (BCC). Prolonged sun exposure of the skin causes photo-aging, which is associated with actinic elastosis, a condition characterized by the degeneration of elastin in the upper dermis, which is assessable via conventional histology. In this study, we aimed to compare the degree of actinic elastosis in different types of KC with regard to various patient characteristics. (2) Methods: We defined a semiquantitative score for the degree of actinic elastosis ranging from 0 = none to 3 = total loss of elastic fibers (basophilic degeneration). The extent was measured histometrically by two independent dermatohistopathologists in the immediate vicinity of 353 KC. The scores were merged and matched with tumor types (cSCC and BCC with subtypes), and clinical variables such as body site, sex and age. (3) Results: As expected, the degree of actinic elastosis correlated with age. However, it was significantly higher in cSCC compared to BCC irrespective of age, sex, body site and tumor subtypes. (4): Conclusions: Lifetime sun exposure may be estimated via routine histology using this scoring technique for actinic elastosis as a surrogate marker. cSCCs are more strongly associated with chronic UV exposure than BCCs, even in sun-exposed localizations such as the face.

Clear cell variant of atypical fibroxanthoma and pleomorphic dermal sarcoma: molecular characterization and review of the literature

Atypical fibroxanthoma (AFX) and pleomorphic dermal sarcoma (PDS) are unusual cutaneous tumors that typically arise in sun-damaged skin of elderly individuals. Several histopathologic variants have been described, but the clear cell variant is particularly rare with only 18 cases of AFX and 1 case of PDS reported. Here, we present two cases of clear cell AFX and PDS highlighting key histopathologic findings and molecular alterations assessed by next generation sequencing (NGS).

Oncological Safety and Recurrence in the Surgical Treatment of Atypical Fibroxanthoma and Pleomorphic Dermal Sarcoma of the Scalp

Simple Summary

Atypical fibroxanthoma and pleomorphic dermal sarcoma represent two tumors on the spectrum of a rare dermal sarcoma entity. Close clinical presentation and nearly identical histologic features but distinct prognoses make proper treatment strategies challenging. We performed a retrospective analysis of 32 patients with AFX or PDS in the scalp to provide guidance regarding the extent of radical excision to achieve stable oncological outcomes and whether radical tumor resection on the scalps required complex soft-tissue reconstruction. Compared to AFX, PDS shows a more aggressive growth pattern with frequent satellite metastases and distant metastases. These require extensive resections for local control to achieve long-term remission in most PDS patients. Despite the limited elasticity of the scalp, plastic reconstructive procedures can obtain reliable soft tissue reconstruction, even for complete scalp defects. Due to their rarity, managing these tumors requires an interdisciplinary setting in a specialized sarcoma center.

Abstract

Atypical fibroxanthoma (AFX) and pleomorphic dermal sarcoma (PDS) are two distinct designations for a rare dermal sarcoma entity. These tumors arise predominantly in the sun-damaged skin of elderly patients. Although both AFX and PDS have a similar clinical presentation and nearly identical genetic features, they significantly differ in prognosis. Here we present a retrospective single-center chart review analyzing the outcomes of patients treated for dermal sarcoma. The radicality of the tumor-resection extent and soft-tissue reconstructive options were assessed. Patients between January 2010 and August 2021 were included. We recorded resection margins, tumor recurrence, overall survival, number of operations until complete tumor resection, and reconstructive procedures; any complications were recorded. Furthermore, we analyzed a subgroup of patients with satellite metastases. A total of 32 patients met the inclusion criteria (30 male, 2 female, median age of 77.5 years (interquartile range (IQR) 74–81)). Histopathology revealed AFX in 14 patients and PDS in 18 patients. Margin-free resection was achieved in 31 cases, and 27 patients were remission free over the reported period. The local recurrence rate was 5, and distant metastasis was detected in four cases. Of all the PDS cases, nine presented with satellite metastasis. No AFX had satellite metastases. Due to their rarity, managing these tumors requires an interdisciplinary setting in a specialized sarcoma center.

Risk factors for local atypical fibroxanthoma recurrence and progression to pleomorphic dermal sarcoma: A meta-analysis of individualized participant data

Background

Risk factors for local atypical fibroxanthoma (AFX) recurrence and progression to pleomorphic dermal sarcoma (PDS) have not previously been identified.

Objective

To identify risk factors and provide follow‐up suggestions for local AFX recurrence and progression to PDS.

Methods and Materials

A literature search was performed in the PubMed, EMBASE, and Cochrane databases. The PRISMA and MOOSE guidelines were followed. The risks of local AFX recurrence and progression to PDS were presented as Kaplan–Meier plots and risk factors were presented as hazard ratios (HRs) calculated with univariate and multivariate Cox regression.

Results

Five hundred and ninety‐eight patients with AFX from 14 studies were included. Age >74 years and male sex significantly increased the risk of local recurrence (HR: 7.31 [95% confidence interval [CI]: 1.78–30.0], p < 0.01 and HR: 2.89 [95% CI: 1.04–8.01], p < 0.05, respectively). There was no difference when comparing wide local excision and Mohs' micrographic surgery (p = 0.89). The risks of local AFX recurrence and progression to PDS after 2 years were <1%.

Conclusion

A more intensive follow‐up regimen could be considered in patients >74 years old and males due to the higher risk of local AFX recurrence.

A Multidisciplinary Approach to Complex Dermal Sarcomas Ensures an Optimal Clinical Outcome

Primary dermal sarcomas (PDS) belong to a highly clinically, genetically and pathologically heterogeneous group of rare malignant mesenchymal tumours primarily involving the dermis or the subcutaneous tissue. The tumours are classified according to the mesenchymal tissue from which they originate: dermal connective tissue, smooth muscle or vessels. Clinically, PDS may mimic benign soft tissue lesions such as dermatofibromas, hypertrophic scarring, etc. This may cause substantial diagnostic delay. As a group, PDS most commonly comprises the following clinicopathological forms of dermal sarcomas: dermatofibrosarcoma protuberans (DFSP), atypical fibroxanthoma (AFX), dermal undifferentiated pleomorphic sarcoma (DUPS), leiomyosarcoma (LMS), and vascular sarcomas (Kaposi’s sarcoma, primary angiosarcoma, and radiation-induced angiosarcoma). This clinical entity has a broad spectrum regarding malignant potential; however, local aggressive behaviour in some forms causes surgical challenges. Preoperative, individualised surgical planning with complete free margins is pivotal along with a multidisciplinary approach and collaboration across highly specialised surgical and medical specialties. The present review gives a structured overview of the most common forms of dermal sarcomas including surgical recommendations and examples for advanced reconstructions as well as the current adjunctive medical treatment strategies. Optimal aesthetic and functional outcomes with low recurrence rates can be achieved by using a multidisciplinary approach to complex dermal sarcomas. In cases of extended local tumour invasion in dermal sarcomas, advanced reconstructive techniques can be applied, and the interdisciplinary microsurgeon should be an integral part of the sarcoma board.

Cutaneous atypical fibroxanthoma with osteoclast-like giant cell: a rare phenomenon

Atypical fibroxanthoma with osteoclast-like giant cells is a rare entity. We present the case of an elderly woman who presented with a pink-purple dome-shaped nodule with central hyperkeratotic crust. Biopsy revealed a cellular, dermal based tumor comprised of spindle, oval, and osteoclast-like giant cells with pleomorphism. The immunohistochemistry profile supported a diagnosis of atypical fibroxanthoma (AFX) with osteoclast-like giant cells. We performed a literature review through PubMed and Google Scholar for AFX with osteoclast-like giant cell formation and found 16 previously reported cases. We aim to provide a review and discuss features of these cases. We also discuss the pathogenesis of these osteoclast-like cells as well as potential pitfalls in diagnosis. This article is protected by copyright. All rights reserved.

Atypical Fibroxanthoma Demonstrating HMB45+ Staining

ABSTRACT

Immunohistochemistry is useful and often necessary for the diagnosis of many histopathological entities, including atypical fibroxanthoma (AFX), which is typically considered a diagnosis of exclusion after ruling out spindle cell melanoma, sarcomatoid carcinoma, and other spindle cell tumors. AFX is a superficial fibrohistiocytic tumor previously believed to be related to pleomorphic sarcoma (formerly known as malignant fibrous histiocytoma), but is now considered a distinct clinicopathological entity. AFXs commonly express CD68, smooth muscle actin, and lysozyme and are usually negative for melanocytic markers such as HMB45 and S100. However, immunohistochemistry can sometimes be misleading, especially when used without other relevant markers in making a histopathologic diagnosis. HMB45 is a glycoprotein marker of premelanosomes and is often helpful in identifying melanoma because it stains melanosomes in the epidermis, dermis, and nevi glycocomplexes. We report a case of AFX which was strongly positive for HMB45, but negative for all other melanocytic markers. This case emphasizes the potential pitfall of relying on a single immunohistochemical marker to make the diagnosis, especially of melanoma, and also is one of the only rare reported cases of AFXs which are HMB45+.

Pleomorphic dermal sarcoma: Clinicopathological features and outcomes from a 5-year tertiary referral centre experience

BACKGROUND

Pleomorphic dermal sarcoma (PDS) describes rare dermal-based malignant tumours that are morphologically similar to atypical fibroxanthoma (AFX). PDS may be differentiated from AFX by the presence of one or more of the following histologic features: subcutaneous invasion, tumour necrosis, lymphovascular invasion (LVI), and/or perineural infiltration (PNI).

AIMS

To further define the clinicopathological features, surgical management, and outcomes of PDS primary tumours.

METHODS AND RESULTS

This study was a retrospective observational case series using a database search from 2012 to 2017. Inclusion criteria required all cases to meet the histopathologic criteria for PDS as confirmed by a specialist soft-tissue histopathologist. A total of n = 17 cases were included with a median age of 78 years (range 66-85). All tumours were located on the head and neck, with 13/17 located on the scalp. Primary treatment was with wide local excision (WLE) in all cases. Median follow-up was 48 months. Local recurrence occurred in 4/17 cases (24%) and distant metastasis in 2/17 cases (12%).

CONCLUSION

PDS behaves more aggressively than atypical fibroxanthoma with which it shares a biologic continuum. The optimal surgical management approach is yet to be determined.

Undifferentiated and dedifferentiated soft tissue neoplasms: Immunohistochemical surrogates for differential diagnosis

Undifferentiated soft tissue sarcomas (USTS) are described in the current World Health Organization Classification of Soft Tissue and Bone Tumours as those showing no identifiable line of differentiation when analyzed by presently available technologies. This is a markedly heterogeneous group, and the diagnosis of USTS remains one of exclusion. USTS can be divided into four morphologic subgroups: pleomorphic, spindle cell, round cell and epithelioid undifferentiated sarcomas, with this combined group accounting for up to 20% of all soft tissue sarcomas. As molecular advances enable the stratification of emerging genetic subsets within USTS, particularly within undifferentiated round cell sarcomas, other groups, particularly the category of undifferentiated pleomorphic sarcomas (UPS), still remain difficult to substratify and represent heterogeneous collections of neoplasms often representing the common morphologic endpoints of a variety of malignant tumors of various (mesenchymal and non-mesenchymal) lineages. However, recent molecular developments have also enabled the identification and correct classification of many tumors from various lines of differentiation that would previously have been bracketed under 'UPS'. This includes pleomorphic neoplasms and dedifferentiated neoplasms (the latter typically manifesting with an undifferentiated pleomorphic morphology) of mesenchymal (e.g. solitary fibrous tumor and gastrointestinal stromal tumor) and non-mesenchymal (e.g. melanoma and carcinoma) origin. The precise categorization of 'pleomorphic' or 'undifferentiated' neoplasms is critical for prognostication, as, for example, dedifferentiated liposarcoma typically behaves less aggressively than other pleomorphic sarcomas, and for management, including the potential for targeted therapies based on underlying recurrent molecular features. In this review we focus on undifferentiated and dedifferentiated pleomorphic and spindle cell neoplasms, summarizing their key genetic, morphologic and immunophenotypic features in the routine diagnostic setting, and the use of immunohistochemistry in their principal differential diagnosis, and highlight new developments and entities in the group of undifferentiated and dedifferentiated soft tissue sarcomas.

Cutaneous soft tissue sarcomas: survival-related factors

Cutaneous sarcomas are a heterogeneous group of rare mesenchymal neoplasms representing less than 1% of malignant tumors. Histology report remains the cornerstone for the diagnosis of these tumors. The most important clinicopathologic parameters related to prognosis include larger tumor size, high mitotic index, head and neck location, p53 mutations, depth of infiltration and histological grade, vascular and perineural invasion as well as the surgical margins status. Applying advanced biopsy techniques might offer more precise assessment of surgical margins, which constitutes a significant precondition for the management of these tumors. The management of cutaneous soft tissue sarcomas requires a multidisciplinary approach. Surgery remains the standard treatment, nonetheless adjuvant therapy may be required, consisting of radiotherapy, chemotherapy, and molecular targeted therapies to improve treatment outcomes. The role of molecular profiling in the treatment of uncontrolled disease is promising, but it may be offered to a relatively small proportion of patients and its use is still considered experimental in this setting. Due to the rarity of the disease, there is a need for knowledge and experience to be shared, pooled, organized and rationalized so that recent developments in medical science can have a major impact on the disease course. Multicenter clinical trials are needed to improve the care of patients with cutaneous sarcomas.

Pleomorphic dermal sarcoma: a clinical and histological review of 49 cases

Pleomorphic dermal sarcoma (PDS) is a rare mesenchymal neoplasm that shares histopathological features with atypical fibroxanthoma (AFX), but has additional features of deep invasion of the superficial subcutis, tumour necrosis, and vascular and perineural invasion, which confers a risk of local recurrence and metastases. To study the clinical and pathological spectrum more comprehensively, we retrieved 49 cases of pleomorphic dermal sarcoma from our departmental files. There was a strong male predominance (n=45). The mean (range) age at presentation was 80 (47-97) years. The tumours had a median (range) maximum dimension of 23.5 (5-75) mm. There was a strong predilection for the head and face (n=47), with the scalp (n=32) being the most common site. Ulceration was observed in 21 patients, tumour necrosis in seven, perineural infiltration in six, and lymphovascular invasion in two. CD10 was expressed in all cases. Smooth muscle actin was expressed in 15 and CD68 in 14. Follow up was available in 41 cases (mean (range) 22.4 (2-90) months). Six patients had local recurrences, despite all having originally undergone primary surgical resections and having reports of clear margins. Progressive metastatic disease was observed in one patient who died from their disease. Based on the Kaplan Meier method, median overall survival was 70.8 (8.4-133.1) months. Although AFX and PDS may be part of a spectrum, distinction is important to emphasise the potential for malignant behaviour in PDS.

Atypical fibroxanthoma: An analysis of 105 tumors

Atypical fibroxanthoma (AFX) is a rare, low-grade dermal sarcoma. We analyzed our files from January 2001 to January 2020 for AFX. Clinical parameters, histopathology, treatment and outcome have been investigated. We identified 87 patients (mean age of 80.0 ± 8.4 years) with 105 confirmed tumors. Of these patients 86.2% were males. The most common clinical presentation was nodular (93.3%). The majority of AFX was located on the head with a mean tumor diameter of 15.0 mm ± 3.5 mm. All tumors showed a dermal localization, in 46.4% with a focal infiltration of the deeper layers. Second skin cancer was reported in 62.1% of patients. Collision tumors were seen in six patients. Treatment was surgical with three-dimensional margin control. Relapses were noted in 11.4% of tumors with a mean delay of 11.7 ± 17.3 months. Focally deeper infiltration of AFX was a risk factor (P = .014). None of the purely dermal AFX relapsed. No metastasis was observed. AFX is a rare mesenchymal tumor of elderly patients. Treatment of choice is the complete surgical excision. Due to the high rate of other skin malignancies among patients with AFX, a regular follow-up is recommended.

Soft Tissue Special Issue: Cutaneous Pleomorphic Spindle Cell Tumors

This manuscript provides an overview of pleomorphic spindle cell tumors presenting on sun-damaged skin of the elderly and includes discussions of atypical fibroxanthoma, pleomorphic dermal sarcoma, spindle cell and metaplastic squamous cell carcinoma, spindle cell and dedifferentiated melanoma and poorly differentiated cutaneous angiosarcoma. These tumors share many of the clinical presenting and histological features, making confident diagnosis challenging. A reliable and robust diagnosis is necessary to predict behavior as the biologic potential of these tumors ranges from benign (e.g. atypical fibroxanthoma) to outright malignant with poor survival rates (e.g. cutaneous angiosarcoma). The salient clinical, histologic and immunohistochemical characteristics are discussed in detail with emphasis on distinguishing features and differential diagnosis to provide the reader with a better understanding of these entities and helpful clues for a more robust diagnosis.

Pleomorphic Sarcomas: The State of the Art

This article focuses on pleomorphic sarcomas, which are malignant mesenchymal tumors with complex genetic background at the root of their morphologic pleomorphism. They are poorly differentiated tumors that may retain different lines of differentiation, sometimes correlating with clinicopathological or prognostic features. Accurate diagnosis in this group of tumors relies on adequate sampling due to their heterogeneity and assessment with both microscopy and large panels of immunohistochemistry. Molecular analyses have a limited role in their diagnosis as opposed to translocation-related sarcomas but may provide theranostic and important prognostic information in the future.

Case for diagnosis. Atypical fibroxanthoma

Atypical fibroxanthoma is a rare superficial fibrohistiocytic tumor. Clinically, it presents itself as a painless, solitary, ulcerated, and slow-growing nodule found mainly on sun-exposed areas - especially of the head and neck - of elderly individuals. The diagnosis is based on histopathological and immunohistochemical features. Immunohistochemical staining plays a critical role for the exclusion of differential diagnoses. Since atypical fibroxanthoma has an indolent clinical course, surgical excision is adequate for treatment. We present a case of atypical fibroxanthoma on the ear of a patient.

MYC gene amplification is a rare event in atypical fibroxanthoma and pleomorphic dermal sarcoma

Atypical fibroxanthoma (AFX) and pleomorphic dermal sarcoma (PDS) are rare malignancies typically occurring in elderly patients and predominantly located in skin regions exposed to UV-light. Thus, a role of UV-radiation-induced damage for AFX and PDS tumorigenesis has been postulated. MYC gene amplification has been demonstrated as a distinctive feature of radiation-induced angiosarcoma. In order to investigate whether chronic exposure to UV-light might also lead to MYC copy number changes, 51 AFX and 24 PDS samples were retrospectively analyzed for MYC amplification by fluorescence in situ hybridization using a MYC and a CEP8 gene probe. Of the 44 analyzable AFX samples, one case showed MYC amplification (defined as a MYC/CEP8 ratio ≥2.0), whereas 13 cases demonstrated low level copy number gains (defined as MYC/CEP8 ratio ≥ 1.2-< 2.0). MYC amplification was seen in an AFX sample of extraordinary tumor thickness of 17.5 mm (vs. median 3.25 mm for all samples). Of the 24 PDS cases, five specimen demonstrated MYC low level copy number gains. Immunohistochemically, neither the AFX nor the PDS cases showed MYC protein expression. In summary, these findings rule out that MYC amplification is a major genetic driver in the process of AFX or PDS tumorigenesis. However, MYC amplification may occur as a late event during AFX development and hence might only be detectable in advanced, thick lesions.

Dermoscopy features of atypical fibroxanthoma: A multicenter study of the International Dermoscopy Society

BACKGROUND/OBJECTIVES

Little is known about the dermoscopic features of atypical fibroxanthoma.

METHODS

This was a case-control study. Atypical fibroxanthoma lesions were compared with a control group with non-melanoma skin cancer.

RESULTS

Altogether 40 atypical fibroxanthoma were collected. Most developed in men (93%), appearing mainly as nodular (63%), amelanotic (93%) and ulcerated (78%) lesions. Most lesions were located on the scalp (55%) and the ears (13%). Dermoscopically, most atypical fibroxanthoma displayed red (83%) and white (70%) structureless areas and irregular linear vessels (43%). A series of features achieved statistical significance when comparing atypical fibroxanthoma with non-melanoma skin cancer. The presence of red and white structureless areas and white lines, and the absence of yellowish-white opaque scales, hairpin vessels and arborising vessels were predictive of atypical fibroxanthoma in univariate analysis. However, when squamous cell carcinoma was excluded from the analysis, none of the criteria achieved statistical significance. When basal cell carcinoma was excluded, three variables achieved statistical significance in predicting atypical fibroxanthoma: red, structureless areas, the absence of opaque yellowish-white scales and absence of white circles.

CONCLUSIONS

Atypical fibroxanthomas seem to be barely distinguishable from basal cell carcinoma dermoscopically, but they are more easily distinguishable from a well to moderately differentiated squamous cell carcinoma. A histopathological examination is needed for the final diagnosis.

Cutaneous/subcutaneous mesenchymal proliferations of the breast

Cutaneous mesenchymal "spindle cell" lesions arising in the vicinity of the breast represent a complex clinical and diagnostic scenario which may overlap histopathologically and immunohistochemically with mammary spindle cell proliferations, potentially impacting management and overall prognostication. In this review, we suggest a pattern-based approach to assist in the evaluation of these lesions. A comprehensive description of each entity is accompanied by a cutaneous and mammary differential diagnosis.

Atypical Fibroxanthoma Revisited

Atypical fibroxanthoma (AFX) represents a rare mesenchymal neoplasm arising predominantly in the head and neck area of elderly patients. Clinically, the neoplasm is characterized by a rapid and exophytic growth with frequent ulceration of the epidermis. Histopathologically, AFX represents a well-circumscribed, dermal-based neoplasm composed of a variable admixture of large histiocytoid cells, enlarged spindled and epithelioid tumor cells, and multinucleated tumor giant cells with bizarre and pleomorphic nuclei. If strict diagnostic criteria are applied, the clinical behavior of AFX is benign in most cases, and complete excision represents the treatment of choice.

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.

Atypical Fibroxanthoma

Atypical fibroxanthoma is a malignant skin tumor with histologic features similar to those of undifferentiated pleomorphic sarcoma, but lacking its more aggressive behavior. The tumor is composed of pleomorphic cells with hyperchromatic nuclei and abundant cytoplasm, commonly arranged in a spindle cell pattern. Recent genetic studies have identified similarities between atypical fibroxanthoma and undifferentiated pleomorphic sarcoma, such as the presence of 9p and 13q deletions in both tumors, favoring a common histogenesis. However, the lack of K-ras and H-ras mutations in atypical fibroxanthoma compared with undifferentiated pleomorphic sarcoma could explain the difference in aggressiveness and continued separation of these entities. Exclusion of other neoplasms by histology and immunohistochemistry followed by complete surgical removal remains the standard of care.

Clear cell atypical fibroxanthoma: a case report and review of the literature

Atypical fibroxanthoma (AFX) is a group of cutaneous tumors characterized by a population of fusiform, epithelioid and pleomorphic cells. Clinically, AFX is commonly found on the head and neck of older adults as a solitary ulcerated nodule. Clear cell atypical fibroxanthoma is a very rare variant of AFX, with only 13 cases reported to date. The differential diagnoses often include dermal neoplasms composed of clear cells, such as squamous cell carcinoma, basal cell carcinoma, metastatic renal cell carcinoma and balloon cell malignant melanoma. These diagnoses can be ruled out by the typical immunohistochemical profile of clear cell AFX, which is negative for specific epithelial and melanocytic markers. Herein, we describe a rare and unusual case of clear cell AFX arising on the ear of a relatively young adult patient. Histologically, the dermis was completely replaced by an atypical population of vacuolated cells with numerous atypical mitoses. Immunohistochemical stains were negative forpancytokeratin, CK5/6, CK7, and p63 S100 and Melan-A stains. CD10 and CD68 stains were positive, making the findings consistent with the diagnosis of clear cell atypical fibroxanthoma.