Procollagen 1 expression in atypical fibroxanthoma and other tumors

Increase of atypical fibroxanthoma and pleomorphic dermal sarcoma: a retrospective analysis of four German skin cancer centers

BACKGROUND AND OBJECTIVES

In recent years, considerable insight has been gained into the pathogenesis, diagnosis and treatment of cutaneous sarcomas, including atypical fibroxanthoma (AFX) and pleomorphic dermal sarcoma (PDS). Both entities have shown increasing incidence rates in the last decade. This study was initiated to evaluate how these new insights impact the number of diagnoses of AFX/PDS compared to other cutaneous sarcoma entities.

PATIENTS AND METHODS

In a retrospective study of four German skin cancer centers, all histopathological reports of cutaneous sarcomas (AFX, PDS, dermatofibrosarcoma protuberans, cutaneous leiomyosarcoma, angiosarcoma, and Kaposi sarcoma) confirmed by board-certified dermatopathologists were analyzed during a time-period of seven years (2013-2019). Additionally, utilization of immunohistochemical markers (including pan-cytokeratin, S100, desmin, CD34, CD10, procollagen-1, CD99, CD14, and CD68) as an adjunct to diagnose AFX/PDS was recorded.

RESULTS

Overall, 255 cutaneous sarcomas were included in the present study. The diagnosis of a cutaneous sarcoma has consequently risen from 2013 to 2019 (from 16 to 52 annual cases). The results of AFX/PDS revealed 4.6 times more diagnoses in 2019 than in 2013. Atypical fibroxanthoma represented the most common subtype, displaying 49.3 % of all diagnosed cutaneous sarcomas. Additionally, the increase of AFX/PDS was linked to the use of immunohistochemistry, with specific immunohistochemical markers used in 57.1 % of cases in 2013 compared to 100 % in 2019.

CONCLUSIONS

This retrospective study of four German skin cancer centers demonstrates a substantial rise of AFX/PDS, possibly due to recently established diagnostic and terminology standards. This rise is probably linked to increased utilization of specific immunohistochemical markers. Atypical fibroxanthoma/PDS may be more common than previously thought and seems to represent the most frequent cutaneous sarcoma subtype.

Zunahme des atypischen Fibroxanthoms und pleomorphen dermalen Sarkoms: eine retrospektive Analyse vier deutscher Hauttumorzentren

HINTERGRUND UND ZIELE

In den letzten Jahren konnten umfassende Erkenntnisse über die Pathogenese, Diagnostik und Behandlung von kutanen Sarkomen, insbesondere des atypischen Fibroxanthoms (AFX) und pleomorphen dermalen Sarkoms (PDS) gesammelt werden. Beide Entitäten zeigten innerhalb der letzten Dekade steigende Inzidenzraten. Die vorliegende Studie diente der Untersuchung, welchen Einfluss die neuen Erkenntnisse auf die Fallzahlen von AFX/PDS im Vergleich zu anderen Sarkom-Entitäten haben.

PATIENTEN UND METHODIK

Diese retrospektive Studie wurde an vier deutschen Hauttumorzentren durchgeführt und alle von zertifizierten Dermatopathologen bestätigten histopathologischen Befunde von kutanen Sarkomen (AFX, PDS, Dermatofibrosarcoma protuberans, kutanes Leiomyosarkom, Angiosarkom und Kaposi-Sarkom) in einem Zeitraum von sieben Jahren (2013-2019) evaluiert. Zusätzlich wurde der Einsatz von immunhistochemischen Markern als diagnostische Hilfe (Panzytokeratin, S100, Desmin, CD34, CD10, Prokollagen-1, CD99, CD14 und CD68) erfasst.

ERGEBNISSE

Insgesamt konnten 255 kutane Sarkome in die vorliegende Studie eingeschlossen werden. Die Zahl der kutanen Sarkome nahm kontinuierlich von 2013 bis 2019 zu (von 16 auf 52 Fälle im Jahr). Die Diagnose eines AFX/PDS konnte in 2019 4,6-mal häufiger als in 2013 gestellt werden. Das AFX stellte mit 49,3 % aller kutanen Sarkome den häufigsten Sarkom-Subtypen dar. Zusätzlich war der Anstieg von AFX/PDS mit dem Einsatz von Immunhistochemie assoziiert. Der Einsatz von spezifischen Immunhistochemischen Markern stieg von 57,1 % im Jahr 2013 auf 100 % in 2019.

SCHLUSSFOLGERUNGEN

Diese retrospektive Studie von vier deutschen Hauttumorzentren demonstriert eine substanzielle Zunahme von AFX/PDS, wahrscheinlich infolge kürzlich etablierter beziehungsweise verbesserter diagnostischer und terminologischer Standards. Dieser Anstieg ist vermutlich mit dem vermehrten Einsatz von bestimmten immunhistochemischen Markern assoziiert. AFX/PDS treten wahrscheinlich häufiger auf als bisher vermutet und repräsentieren möglicherweise den häufigsten kutanen Sarkom-Subtyp.

Clear-Cell Atypical Fibroxanthoma: A Combined Immunohistochemistry Analysis

Atypical fibroxanthoma is considered to be a low-grade sarcoma, characterized by a proliferation of bizarre spindled cells. A case of a rare variant of this tumor, a clear-cell atypical fibroxanthoma, presenting with rapid growth on a 63-year-old female, is reported. The differential diagnosis of a clear cell proliferation and a review of the immunohistochemistry markers used in the diagnosis of atypical fibroxanthoma are discussed. In particular, the usefulness of markers such as CD10, procollagen 1, CD68, CD163, CD99, and S100A6, and the importance of negative markers such as S100, cytokeratin, and desmin are emphasized. Furthermore, the development of a keratoacanthoma at the site of previous Mohs surgery is recounted.

Immunohistochemistry in dermatopathology

CONTEXT

Immunohistochemistry is not a diagnostic test but a highly valuable tool that requires interpretation within a context.

OBJECTIVE

To review the current status and limitations of immunohistochemistry in dermatopathology.

DATA SOURCES

English-language literature published between 1980 and 2014.

CONCLUSIONS

Although immunohistochemistry is rarely completely specific or sensitive, it is an important adjunctive technique in dermatopathology and can be helpful in a series of diagnostic dilemmas.

Atypical fibroxanthoma: new insights

Atypical fibroxanthoma (AFX) is an ultraviolet radiation-associated dermal neoplasm. To address the clinicopathologic and molecular features of this particular neoplasm. The author conducted a literature review using PubMed searching for articles relating to AFX. AFX usually appears as a rapidly growing nodular or nodulo-ulcerative lesion. It occurs on sun-exposed skin of elderly peoples. AFX may be composed predominantly of pleomorphic, spindle, epithelioid cells, or admixture of these cells. The differential diagnosis of AFX includes pleomorphic dermal sarcoma, squamous cell carcinoma, malignant melanoma and leiomyosarcoma. Several observations favor a mesenchymal origin for AFX. These reviews address the clinicopathologic features, molecular pathology, prognosis and treatment of this neoplasm.

TERT promoter mutations are frequent in atypical fibroxanthomas and pleomorphic dermal sarcomas

Activating mutations in the TERT promoter leading to increased telomerase expression were recently identified in cutaneous melanoma and subsequently in many other types of cancer. These mutations lead to increased telomerase expression, allowing cells to proliferate continuously without entering apoptosis or senescence. Atypical fibroxanthomas and pleomorphic dermal sarcomas are genetically poorly understood tumors developing in the skin of older patients. Known genetic events in these tumors are mutations in TP53 (atypical fibroxanthoma and pleomorphic dermal sarcoma) and RAS (pleomorphic dermal sarcoma) genes, often having a UV signature. We analyzed a cohort of 27 atypical fibroxanthomas and 34 pleomorphic dermal sarcomas for the presence of TERT promoter mutations by conventional Sanger sequencing. TERT promoter mutations were identified in 25 (93%) atypical fibroxanthomas and in 26 (76%) pleomorphic dermal sarcomas. Mutations were found to have a UV signature (C>T or CC>TT) and were largely identical to those detected in cutaneous melanoma. Our data show that TERT promoter mutations are the most frequent mutations in atypical fibroxanthomas and pleomorphic dermal sarcomas reported to date. The identified mutations confirm the pathogenetic role of UV exposure in both atypical fibroxanthomas and pleomorphic dermal sarcomas and suggest that telomere maintenance through increased expression of telomerase plays an important role in the pathogenesis of these tumors.

Simulators of squamous cell carcinoma of the skin: diagnostic challenges on small biopsies and clinicopathological correlation

Squamous cell carcinoma (SCC) is a common and important primary cutaneous malignancy. On skin biopsies, SCC is characterized by significant squamous cell atypia, abnormal keratinization, and invasive features. Diagnostic challenges may occasionally arise, especially in the setting of small punch biopsies or superficial shave biopsies, where only part of the lesion may be assessable by the pathologist. Benign mimics of SCC include pseudoepitheliomatous hyperplasia, eccrine squamous syringometaplasia, inverted follicular keratosis, and keratoacanthoma, while malignant mimics of SCC include basal cell carcinoma, melanoma, and metastatic carcinoma. The careful application of time-honored diagnostic criteria, close clinicopathological correlation and a selective request for a further, deeper, or wider biopsy remain the most useful strategies to clinch the correct diagnosis. This review aims to present the key differential diagnoses of SCC, to discuss common diagnostic pitfalls, and to recommend ways to deal with diagnostically challenging cases.

Nonepithelial skin tumors with multinucleated giant cells

Recognition of the different types of multinucleated giant cells in neoplastic and pseudotumoral lesions of the skin may be helpful in the differential diagnosis of these tumors. In this review, we will analyze the different types of multinucleated giant cells that can be found in nonepithelial cutaneous tumors and, more importantly, the clinicopathological context in which they are found. Touton giant cells are typically present in juvenile xanthogranuloma, necrobiotic xanthogranuloma, and some subtypes of xanthomas. Giant cells with a ground glass appearance are typically present in the solitary reticulohistiocytoma and multicentric reticulohistiocytosis. Osteoclast-like cells are found in giant cell tumors (GCT) of soft parts, plexiform fibrohistiocytic tumor, and atypical fibroxanthoma. Floret-like cells are present in giant cell fibroblastoma, pleomorphic lipoma, multinucleate cell angiohistiocytoma, and giant cell collagenoma.

Granular cell atypical fibroxanthoma: case report and review of the literature

We present a case of granular cell atypical fibroxanthoma of the scalp. The neoplasm occurred as a tender nodule on the frontal scalp of an 82-year-old Caucasian man. Histology demonstrated a diffuse proliferation of atypical epithelioid cells with abundant granular cytoplasm. Many of the cells had large irregular nuclei and atypical mitotic figures were present. Immunohistochemical stains were positive for CD68 and procollagen 1 and negative for cytokeratin, HMB-45 and S-100 protein. The granular cell phenotype has been observed in other cutaneous neoplasms including granular cell tumors, dermatofibromas, dermatofibrosarcoma protuberans, fibrous papules, basal cell carcinomas, leiomyosarcomas, angiosarcomas and primitive polypoid granular cell tumors. We discuss the differential diagnosis and review the previously reported cases of this rare variant of atypical fibroxanthoma.

CD10, p63 and CD99 expression in the differential diagnosis of atypical fibroxanthoma, spindle cell squamous cell carcinoma and desmoplastic melanoma

BACKGROUND

Atypical fibroxanthoma (AFX) is a pleomorphic spindle cell lesion of the skin; it is considered in the differential diagnosis with spindle cell malignant melanoma (MM) and sarcomatoid carcinoma/spindle cell squamous cell carcinoma (SCC). An optimum approach has yet to fully emerge with respect to the immunohistochemical discrimination of these lesions.

METHODS

Departmental archives from 1978 onwards were searched for clinicopathologically confirmed cases of AFX, MM and SCC. Immunostains for CD10, CD99 and p63 were performed in each case. Scored staining results were analyzed using Fisher's Exact Test.

RESULTS

Twenty-seven of 31 cases of AFX were positive for CD10, as compared with 3 of 22 SCCs and 0 of 20 MMs. CD10 positivity was preferentially associated with the diagnosis of AFX (p < 0.001). p63 reactivity was observed in 15/22 cases of SCCs, 5/31 AFXs and 1/20 MMs. CD99 reactivity was observed in 3/31 cases of AFX, 2/22 SCCs and 3/20 MMs.

CONCLUSION

CD10 positivity is relatively specific in this context for the diagnosis of AFX. Its utility is enhanced when only strong, diffuse membranocytoplasmic staining is considered as a positive result. In contrast to prior reports, p63 was not found to be highly sensitive for SCC. Similarly, CD99 showed no preferential staining of any single diagnostic group of lesions.

Immunohistochemistry in the diagnosis of cutaneous neoplasms

In recent years, there has been a significant increase in the number of diagnostic immunohistochemical stains available to pathologists and dermatopathologists. Immunohistochemistry has become an indispensable tool in dermatopathology, not only in diagnosis but also in the treatment and prognostication of cutaneous neoplasms. In this review we attempt to outline current, as well as new, immunohistochemical stains of relevance in the diagnosis and classification of cutaneous neoplasms.

Diagnostic value of CD163 in cutaneous spindle cell lesions

BACKGROUND

The histologic diagnosis of atypical fibroxanthoma (AFX) can sometimes be challenging. No specific marker exists to confirm the diagnosis other than excluding other entities. CD163 has been shown to have great specificity for tumors of monocyte/histiocyte lineage. In this study, we evaluated the diagnostic utility of CD163 in diagnosing AFX and in identifying skin lesions with histiocytic/dendritic derivation.

METHODS

A total of 157 cases, including 14 AFXs, 5 spindle cell squamous cell carcinomas (SCCs), and 7 spindle cell/desmoplastic melanomas, along with other cutaneous spindle cell and histiocytic/fibrohistiocytic lesions, were stained with CD163.

RESULTS

CD163 was expressed in 11 of 14 (79%) AFXs, with moderate to strong intensity. No staining was observed in cases of spindle cell SCC (0/5) and dermatofibrosarcoma protuberans (0/10). Rare spindle cell/desmoplastic melanomas (2/7) and cutaneous leiomyosarcomas (1/5) demonstrated positive staining. CD163 reactivity was seen in 24 of 29 of benign fibrous histiocytomas (BFHs), including 8 of 8 cellular fibrous histiocytomas and 6 of 9 epithelioid cell histiocytomas. The majority of cutaneous histiocytic lesions, including juvenile xanthogranuloma, Langerhans cell histiocytosis and Rosai-Dorfman disease, were positive for CD163.

CONCLUSION

CD163 is a useful adjunct in distinguishing AFX from other malignant cutaneous spindle cell tumors and offers improved specificity in identifying cutaneous histiocytic/dendritic lesions.

Morphological and immunohistochemical characteristics of atypical fibroxanthoma with a special emphasis on potential diagnostic pitfalls: a review

The present manuscript gives emphasis on recognizing different morphological variants of atypical fibroxanthoma (AFX), on validation of immunohistochemical markers and on discussing potential diagnostic pitfalls.

MATERIAL AND METHODS

Histological features analyzed in 66 AFXs were: ulceration, morphological variants, growth pattern, location in the skin and vascular/perineural invasion. The antibodies used were CK-MNF116, CK-AE1/AE3, S100, smooth muscle actin, desmin, CD31 and EMA.

RESULTS

The study included 59 males, 7 females, aged 55-95 years, mean 77 years. All developed on sun damaged skin. Ulceration was present in 50%. Morphological patterns were pleomorphic spindle and epithelioid cells (60.6%), predominantly spindle cells (19.7%), purely spindle-cells (13.6%), and predominantly epithelioid cells (6.1%). Most were localized in the dermis (57.6%). An expansile (36.4%) rather than infiltrative (6.1%) growth into superficial subcutis was also noted. No vascular/perineural invasion was seen. Additional changes were hemorrhagic and pseudoangiomatous areas (24.2%), granular cell change (22.7%), keloid-like areas (9.1%), myxoid change (7.6%), osteoclast-like giant cells (6.1%) and clear cell change (4.6%). AFXs were consistently negative for S100, CK-MNF116, CK-AE1/AE3 and desmin. Focal positivity for SMA (45.2%), EMA (24.4%) and CD 31 (9.5%) was seen.

CONCLUSIONS

A diagnosis of AFX is still made by exclusion of other malignant neoplasms with similar morphology. Immunohistochemistry plays a crucial role in this distinction, but can also be misleading. This study expands the spectrum of non-vascular CD31 positive tumors.

Utility of p63 in the differential diagnosis of atypical fibroxanthoma and spindle cell squamous cell carcinoma

Atypical fibroxanthoma (AFX), spindle cell squamous cell carcinoma (SCSCC) and spindle cell melanoma are the primary entities in the differential diagnosis of a cytologically atypical spindle cell tumor arising on sun-damaged skin. AFX is generally regarded as a diagnosis of exclusion in this context: in the absence of S100 or keratin reactivity, a diagnosis of AFX is favored. However, keratin reactivity may be focal or even absent in SCSCC, and although numerous positive markers of AFX have been proposed, none has shown sufficient sensitivity and specificity for routine diagnostic use. We evaluated 20 AFX and 10 SCSCC with a panel of cytokeratins and p63 to assess the utility of the latter antibody in this differential diagnosis. All 10 SCSCC showed strong expression of p63, whereas all 20 AFX were p63 negative. Two additional cases (excluded from the study) were negative for keratins and S100 on initial shave biopsies, resulting in a favored diagnosis of AFX, but p63 stains performed retrospectively were positive. However, review of the excision specimens in both cases revealed deep subcutaneous extension, excluding AFX. p63 reactivity argues against the diagnosis of AFX and is therefore a useful addition to the standard immunohistochemical panel for cutaneous spindle cell neoplasms.

Evaluation of CD10 and procollagen 1 expression in atypical fibroxanthoma and dermatofibroma

Atypical fibroxanthoma (AFX) (dermal pleomorphic sarcoma) remains a somewhat controversial entity. Some authors have averred that AFX is a fiction, suggesting that such lesions merely represent misclassified examples of spindled squamous cell carcinoma. In addition, the immunoperoxidase confirmation of AFX has been less than straightforward and has historically been approached as a diagnosis of exclusion because of the lack of sensitivity and specificity of available "positive" reagents. Procollagen 1 (PC1) and CD10 represent recently developed immunoperoxidase reagents that have been forwarded as useful in this setting, and we sought to characterize our experience, both to confirm the utility of these antibodies and to compare them. Our investigation included 3 separate data sets. Group 1 consisted of a retrospective review of 98 consecutive cases in which PC1 was used in the evaluation of dermatopathology specimens in routine practice during a 13-month interval. Group 2 consisted of a direct comparison of 11 AFX, 11 dermatofibroma (DF), and 7 epithelioid dermatofibroma (EDF) using the CD10 reagent on cases identified by database search. Group 3 consisted of a retrospective review of 47 cases in which CD10 was used in routine practice during a 10-month interval. Group 1 included 47 AFX, 13 carcinomas, and 6 melanomas. PC1 expression was observed in 45 of 47 AFX (96%), with a strong reaction in 78% of cases. Among a comparison group of carcinomas, 13 of 13 displayed strong keratin immunopositivity and 11 of 13 (85%) lacked PC1 expression whereas 2 showed focal weak labeling. Six of six melanomas exhibited avid S100 expression and none labeled with PC1. In group 2, strong CD10 immunoreactivity was present in 11 of 11 AFX. Similarly, 11 of 11 DFs were also positive. In contrast, 6 of 7 cases of EDF lacked CD10 expression. Group 3 included 38 AFX and 9 miscellaneous spindle cell proliferations. Of the 38 AFX, 37 (97%) labeled with CD10 and in 34 (92%) the reaction was strong. PC1 immunostaining was also completed in 34 of 38 AFX from group 3 and 27 (79%) cases showed positive labeling. Our results confirm that both PC1 and CD10 can be used as positive markers of AFX. We believe that CD10 and PC1 immunostaining can be used as a useful adjunct to supplement the diagnosis of AFX, within the context of an immunoperoxidase panel. Not surprisingly, CD10 expression is also common in DF, a benign analog of AFX, with the exception of its epithelioid variant. In direct head-to-head comparison, our experience indicates that the staining of AFX with CD10 is more avid than that observed with PC1. Lastly, out data includes over 80 examples of AFX, <5% of which showed keratin labeling. Given a general lack of keratin expression, it seems unlikely that AFX merely represents poorly differentiated squamous carcinoma.

Atypical fibroxanthoma presenting in a patient with stage III mycosis fungoides

The association of atypical fibroxanthoma (AFX) and mycosis fungoides (MF) has never been reported. We report a 77-year-old female who was referred for Mohs micrographic surgery (MMS) of an AFX on the right hand. At the time of presentation, this patient had stage III MF, with erythroderma and palpable lymph nodes. Our patient's AFX measured 1.5x2.8 cm. The tumor was removed by MMS with clear margins. The pathologic specimen revealed a relatively well-circumscribed neoplasm in the upper dermis composed of atypical spindle cells with pleomorphism, hyperchromatic nuclei, and brisk mitotic activity. Immunohistochemical stains were focally positive for CD68, and negative for S-100, Melan-A, desmin, smooth muscle actin and neurofilament. Perilesional skin revealed epidermal hyperplasia, parakeratosis, and multiple epidermotropic lymphocytes with enlarged and hyperchromatic nuclei. One year after the initial MMS, our patient developed another tumor on the right hand, which measured 4x6 mm. This neoplasm underwent a fusiform excision with clear margins. Histological examination revealed evidence of MF and an AFX. To our knowledge, this is the first report of an AFX arising in a patient with MF.

Atypical fibroxanthoma

Atypical fibroxanthoma (AFX) is a nodular dermal ulcerative lesion with a favorable prognosis. AFX most commonly occurs on sun-exposed skin in elderly individuals. AFX is characterized by its association with ultraviolet radiation, not only from a clinical aspect, but also from a molecular aspect. Making a diagnosis of AFX is challenging, and it is important to differentiate it from squamous cell carcinoma and malignant melanoma. Histological features and combined immunohistochemical markers are necessary for a definitive diagnosis (i.e., an absence of immunostaining for cytokeratins, S100 and HMB45 in AFX is helpful for excluding both squamous cell carcinoma and malignant melanoma). AFX, as well as MFH (malignant fibrous histiocytoma), is a fibrohistiocytic lesion with myofibroblastic differentiation. AFX is considered to be a different lesion from MFH. AFX and MFH might share the same pathway which determines their morphology. However, they may have different pathways in development which determine their biological behavior.

Selected Diagnostic Problems in Neoplastic Dermatopathology

Context.—Selected cutaneous neoplasms share features with benign counterparts or have subtle morphologic features that could be overlooked by the pathologist.

Objective.—To present clues to the diagnosis of potentially deceptive malignancies, including desmoplastic malignant melanoma, nevoid malignant melanoma, subcutaneous lymphoma, metastatic breast carcinoma, and epithelioid sarcoma.

Data Sources.—Published literature and personal experience.

Conclusions.—Knowledge of commonly misdiagnosed cutaneous neoplasms will help the general surgical pathologist avoid these potential pitfalls in neoplastic dermatopathology.

Diagnosis and management of atypical fibroxanthoma

A 90-year-old Caucasian man with a history of basal cell carcinoma and squamous cell carcinoma presented with a friable erythematous nodule on his scalp that had been present for several months. The lesion measured 1.4 x 1.8 cm. What is your diagnosis? How would you proceed?

Malignant adnexal neoplasms

Malignant cutaneous adnexal neoplasms are one of the most challenging areas of dermatopathology. Tumors of the pilosebaceous apparatus can occur as single-lineage neoplasms or may manifest as complex proliferations with multilineal differentiation patterns including not only the germinative component of the hair bulb, the inner or outer root sheath epithelium and the sebaceous gland and duct, but also the sweat duct components that relate to the apocrine secretory apparatus which empties into the follicle near the follicular bulge. Eccrine and apocrine neoplasms present a bewildering array of morphologies, which often defy precise classification. The purpose of this review is to discuss in detail the malignant neoplasms of the cutaneous adnexae and their benign and prognostically indeterminate mimics.

Metastasizing atypical fibroxanthoma (cutaneous malignant histiocytoma): report of five cases

BACKGROUND

Atypical fibroxanthoma (AFX) is an unusual malignant fibrohistiocytic tumor of sun-damaged skin. When first described, it was felt to be a reactive tumor of low malignant potential. More recently, it has been shown to be a tumor of intermediate malignant potential.

OBJECTIVE

To describe five cases of metastatic AFX.

RESULTS

Five patients ranging in age from 65 to 85 years old presented with metastatic AFX. Three of the five cases presented with regional lymph node disease. Also, three of the five cases had other aggressive cutaneous malignancies. LN-2 (CD74) staining was positive in three of five primary tumors and two of five metastatic tumors.

CONCLUSION

The metastatic potential of AFX may be underestimated. LN-2 staining may be a useful marker in identifying more aggressive tumor behavior.