Decreased Srcasm expression in hyperproliferative cutaneous lesions

Background:  Src-family tyrosine kinases (SFKs) are signaling proteins that regulate keratinocyte proliferation and differentiation. Src-activating and signaling molecule (Srcasm) is a recently identified molecule that downregulates SFK activity and promotes keratinocyte differentiation. To determine if Srcasm expression correlates with keratinocyte differentiation, we characterized the level of Srcasm expression in some cutaneous lesions that exhibit increased keratinocyte proliferation.
Methods:  Formalin-fixed sections of randomly selected seborrheic keratoses (SKs) and basal cell carcinomas (BCCs) were analyzed for Srcasm and Ki-67 immunohistochemical staining. Anti-Srcasm and anti-Ki-67 stainings were performed in parallel.
Results:  All SKs displayed decreased Srcasm staining in areas comprised of basaloid keratinocytes that exhibited an increased Ki-67 index. Higher Srcasm staining levels were detected near pseudohorn cysts where keratinocytes exhibited a lower Ki-67 index. All multicentric and nodular BCCs displayed a prominent loss of Srcasm staining in association with a marked increase in Ki-67 staining.
Conclusions:  Our results support the hypothesis that Srcasm protein levels are decreased in the hyperproliferative keratinocytes found in SKs and BCCs. Increased Srcasm protein levels are detected in keratinocytes undergoing differentiation. Decreased Srcasm levels may be part of the pathophysiologic mechanism in cutaneous lesions, exhibiting keratinocyte hyperproliferation.     

MYC gene numerical aberrations in actinic keratosis and cutaneous squamous cell carcinoma

Background  The genetic alterations that drive the transition from actinic keratoses (AKs) to cutaneous squamous cell carcinomas (SCCs) have not been defined precisely. Amplification and/or overexpression of the MYC proto-oncogene have been demonstrated in several human, malignant tumours including head and neck SCCs.
Objectives  To evaluate the presence of MYC genomic aberrations in both AKs and SCCs.
Methods  Skin biopsy specimens corresponding to AKs, SCCs and control samples were included in two paraffin-embedded tissue microarrays. MYC cytogenetic profile was evaluated by fluorescence in situ hybridization (FISH). The results obtained were compared with MYC immunohistochemical expression.
Results  Twenty-three AKs and 30 SCCs were evaluated. MYC numerical aberrations were observed in eight of 23 (35%) AKs and 19 of 30 (63%) SCCs ( P  = 0·05). MYC numerical aberrations were more frequent in moderately to poorly differentiated SCCs (77%) when compared with well-differentiated SCCs (25%; P  = 0·027). A significant association between copy number gains of MYC by FISH analysis and MYC protein expression was demonstrated.
Conclusions  MYC gains and amplifications are frequent cytogenetic abnormalities in SCCs and may play a relevant role in promoting SCC undifferentiation and tumoral progression.     

Immunopathological study of proliferation-associated antigens in proliferative skin diseases

59 specimens consisting of 10 psoriasis vulgaris, 1 squamous cell carcinoma, 1 Paget disease, 3 keratoacanthomas, 1 pemphigus vulgaris, 18 cutaneous T cell lymphomas, 2 ATLs, and other skin diseases were studied by immunoperoxidase technique. We used four antibodies to demonstrate a cell proliferation-associated antigen (PC, DNA polymerase-alpha and transferrin receptor) and epidermal growth factor receptor. Our observations suggested that the expression of PC and DNA polymerase-alpha may correlate well with cell proliferation, which were demonstrated in the epidermis of psoriasis vulgaris. Primary and metastatic squamous cell carcinoma and some of psoriasis vulgaris had a positive staining for EGF-R, while normal epidermis and almost all other skin diseases were negative.     

Abnormal aquaporin-3 protein expression in hyperproliferative skin disorders

Non-melanoma skin cancers (NMSCs) and psoriasis represent common hyperproliferative skin disorders, with approximately one million new NMSC diagnoses each year in the United States alone and a psoriasis prevalence of about 2% worldwide. We recently demonstrated that the glycerol channel, aquaporin-3 (AQP3) and the enzyme phospholipase D2 (PLD2) interact functionally in epidermal keratinocytes of the skin to inhibit their proliferation. However, others have suggested that AQP3 is pro-proliferative in keratinocytes and is upregulated in the NMSC, squamous cell carcinoma (SCC). To evaluate the AQP3/PLD2 signaling module in skin diseases, we determined their levels in SCC, basal cell carcinoma (BCC) and psoriasis as compared to normal epidermis. Skin biopsies with the appropriate diagnoses (10 normal, 5 SCC, 13 BCC and 10 plaque psoriasis samples) were obtained from the pathology archives and examined by immunohistochemistry using antibodies recognizing AQP3 and PLD2. In normal epidermis AQP3, an integral membrane protein, was localized mainly to the plasma membrane and PLD2 to the cell periphery, particularly in suprabasal layers. In BCC, AQP3 and PLD2 levels were reduced as compared to the normal-appearing overlying epidermis. In SCC, AQP3 staining was “patchy,” with areas of reduced AQP3 immunoreactivity exhibiting positivity for Ki67, a marker of proliferation. PLD2 staining was unchanged in SCC. In psoriasis, AQP3 staining was usually observed in the cytoplasm rather than in the membrane. Also, in the majority of psoriatic samples, PLD2 showed weak immunoreactivity or aberrant localization. These results suggest that abnormalities in the AQP3/PLD2 signaling module correlate with hyperproliferation in psoriasis and the NMSCs.     

Nucleolus organizer regions as useful proliferation markers in hyperproliferative epidermal lesions

Aim To study the suitability of the AgNOR technique for the determination of epidermal proliferative activity in hyperproliferative epidermal lesions. Background Nucleolus organizer regions are nuclear DNA segments of ribosomal genes, which can he visualized in histological sections by using a silver staining technique. Several studies in different tumors have demonstrated that the determination of AgNOR expression makes it possible to obtain precise information on cellular proliferative activity. Methods We investigated the epidermal AgNOR behavior in silver-stained sections of different non-neoplastic hyperproliferative epidermal lesions by image analysis. Results Psoriatic lesions showed the highest AgNOR expression, the lowest AgNOR status was found in senile atrophic epidermis. Acute-exanthematic psoriasis could be distinguished significantly from chronic plaque-type psoriasis. The AgNOR status of lichen planus and verrucous epidermal naevi corresponded to that of normal epidermis. We found a significant correlation with the values of PCNA expression. For analysis of AgNOR expression the count in the basal cell layer is sufficient. Conclusions The AgNOR technique is suitable for estimation of epidermal proliferative activity of hyperproliferative epidermal disorders. The method is easy and can he successfully used in paraffin-embedded tissues.     

Proliferation, apoptosis, and survivin expression in keratinocytic neoplasms and hyperplasias

The dysregulation of apoptosis occurs in many cutaneous disease states. Several apoptosis inhibitors have been shown elevated in neoplasms and in some inflammatory conditions, but their relation to proliferative and apoptotic states has not been defined. We examined the expression of the apoptosis inhibitor survivin in a panel of keratinocytic neoplasms and hyperproliferative skin lesions using both immunohistochemistry and a newly developed in situ hybridization technique. Proliferation and apoptotic indices were also assessed by immunohistochemical staining for proliferating cell nuclear antigen and TUNEL, respectively. We found the highest rate of proliferation in verrucae and psoriasis followed by actinic keratosis, squamous and basal cell carcinoma, lichen simplex chronicus, and seborrheic keratosis; all were significantly (P < 0.05) higher than normal skin. Apoptotic rate was increased in squamous (P = 0.05) and basal cell carcinoma (P = 0.03), but not significantly different from normal skin in the other lesions tested. Survivin expression was seen in most neoplasms and hyperproliferative lesions, but not normal skin. Survivin expression was often restricted to the upper third of the epidermis in psoriasis and lichen simplex chronicus, whereas all the other lesions stained diffusely. Survivin expression appears to be a consistent feature of keratinocytic neoplasms and hyperproliferative lesions and may contribute to the formation of epidermal hyperplasia seen in all of these disease states.     

Fluorescence diagnosis in actinic keratosis and squamous cell carcinoma

Background: As different tissue types have distinct capabilities to accumulate protoporphyrin IX, fluorescence diagnosis with aminolevulinic acid‐induced porphyrins (FDAP) could be used to discriminate between different types of tissue. Previous results demonstrated higher fluorescence ratios in squamous cell carcinoma (SCC) compared with actinic keratoses (AKs). Objectives: The lesional : non‐lesional fluorescence ratio of AKs was compared with the ratio of SCC. Other factors influencing macroscopic fluorescence were also assessed, including stratum corneum thickness, which has been demonstrated to account for heterogeneous fluorescence in psoriasis and in AKs. Methods: After 1 week of keratolytic pretreatment, FDAP was performed in 13 patients with 36 lesions suspected for AK or SCC. Biopsies were taken for histopathological diagnosis and measurement of stratum corneum thickness. Results: No significant differences were found in the fluorescence ratio (lesional : non‐lesional skin) between AKs and SCCs, although macroscopic fluorescence was significantly higher in Bowen's disease and micro‐invasive SCCs. Conclusions: There could be a potential applicability of FDAP to differentiate premalignant lesions with a tendency to progress into SCC and squamous cutaneous lesions already progressing into early invasive cancer from other squamous cutaneous (pre)malignancies. The amount of hyperkeratosis, invasiveness and degree of differentiation seem to be responsible for variations in fluorescence intensity.     

Incipient intraepidermal cutaneous squamous cell carcinoma: a proposal for reclassifying and grading solar (actinic) keratoses

Actinic keratoses (AKs) are primarily induced by ultraviolet (UV) radiation and are often identified as premalignant lesions. In our opinion, AKs are proliferations of transformed, neoplastic keratinocytes confined to the epidermis that may eventually extend into the dermis, at which point they are termed squamous cell carcinoma (SCC). In contrast to AKs, SCCs have the potential to metastasize and kill. This process is analogous to that of evolving carcinoma of the uterine cervix that has been termed cervical intraepithelial neoplasia (CIN), a time-tested and reliable classification that provides clinicians with accurate information on which to base treatment decisions regarding cervical neoplasms following biopsy testing. A similar classification scheme could provide guidance to clinicians for the diagnosis and treatment of evolving SCC of the skin and as such, we propose a similar classification using the terminology keratinocytic intraepidermal neoplasia (KIN). This system is more reflective of the histology and natural history of SCC and eliminates ambiguity in the terminology of lesions currently referred to as AKs. The KIN classification defines features by which individual specimens can be objectively graded and specific treatment recommendations are made based on the grade of the lesion. We propose that the term keratinocytic intraepidermal neoplasia (KIN) be used to define and describe evolving SCC of the skin and that the term actinic (solar) keratosis be eliminated.     

Rapidly‐growing squamous cell carcinoma shortly after treatment with ingenol mebutate for actinic keratoses: report of two cases

Actinic keratoses (AKs) are defined as cutaneous areas of atypical squamous transformation that are regarded as an early step in the continuum of alterations leading from normal skin to invasive and metastatic squamous cell carcinoma (SCC). AKs are classified as precancerous lesions by some authors and in situ SCC by others. The rate of evolution of a given AK to an invasive SCC has been estimated as 0·075–0·096% per lesion per year. These rates are similar to those estimated for gynaecological intraepithelial neoplasia. We describe two cases of SCC with rapid onset that developed after the application of ingenol mebutate gel for the treatment of AKs.     

Expression of minichromosome maintenance 5 protein in proliferative and malignant skin diseases

BACKGROUND: The entire minichromosome maintenance (MCM) family (MCM2-7) play roles in the initiation and elongation of DNA replication. Many studies have demonstrated that MCM proteins may be better indicators of a wide variety of proliferative or cancer cells in malignant tissues. OBJECTIVES: To characterize the pattern and frequency of MCM5 expression in proliferative and malignant skin diseases in comparison with those of proliferating cell nuclear antigen (PCNA). METHODS: Twelve normal skin specimens, 12 specimens of psoriasis, 21 specimens of bowenoid papulosis (BP), 16 specimens of Bowen's disease (BD), 38 specimens of skin squamous cell carcinoma (SCC), and 11 specimens of basal cell carcinoma (BCC) were subjected to immunohistochemical staining for MCM5 and PCNA. Results MCM5 protein was expressed in the lower layers of epidermis in psoriasis, while MCM5 protein were present throughout the tumor cells in BP, BD, and moderately/poorly differentiated SCC. MCM5 protein was preferentially expressed in the periphery of well-differentiated SCC or bigger nests of BCC, although some small nests of BCC seemingly showed diffuse staining patterns. The percentages of MCM5-positive cells were 15.7% in normal skin, 21.8% in psoriasis, 75.9% in BP, 83.8% in BD, 63.5% in well-differentiated SCC, 77.5% in moderately differentiated SCC, 79.8% in poorly differentiated SCC, and 21.2% in BCC in average. Well-differentiated SCC showed a significantly lower percentage of positive cells than did moderately differentiated SCC or poorly differentiated SCC. MCM5 staining basically show a similar staining pattern to that of PCNA, but more cells tended to be stained with MCM5 than with PCNA. CONCLUSIONS: Our results demonstrate pattern and frequency of MCM5 expression in various skin diseases and suggest that MCM5 may be a useful marker to detect cell proliferation in skin tissue sections.     

Differential expression of p63 isoforms in normal skin and hyperproliferative conditions

Background:  The p63 is regarded as a potential stem cell marker.
Methods:  Expression of p63 isoforms was examined in normal skin and hyperproliferative conditions including psoriasis and artificial skin equivalents (SEs). Rapidly adhering (RA) and slowly adhering (SA) cells were isolated, and Western blotting was performed.
Results:  Expression of p63 (4A4) and p63 (H-137) is similar in all conditions, although there is some variation in psoriasis. However, expression of p63α (C-12) is markedly different. In normal skin, p63α (C-12)-positive cells were scattered in whole epidermis. But in psoriasis, p63α (C-12)-positive cells were observed at the tips of rete ridges. In SEs, p63α (C-12)-positive cells were not well observed. Western blot results showed that the RA cells express p63 (4A4) and p63 (H-137) strongly compared with SA or nonadhering (NA) cells. In contrast, SA or NA cells strongly express p63α (C-12).
Conclusions:  Results suggest that both p63 (4A4) and p63 (H-137) can detect epidermal stem cells. But, p63 (H-137) seemed to be a better marker because p63 (H-137)-positive cells were more localized at basal layer. In addition, it can be said that p63α (C-12) can detect TAp63, which is important in differentiation of epidermis. Furthermore, it is concluded that molecular control of TAp63 is especially disorganized in hyperproliferative condition including psoriasis and SEs.     

Expression of matrix metalloproteinase (MMP)-2, MMP-9, MMP-13, and MT1-MMP in skin tumors of human papillomavirus type 8 transgenic mice

Human papillomaviruses (HPV) are small DNA viruses that induce a wide variety of hyperproliferative lesions in cutaneous and mucosal epithelia. It is proposed that HPV is involved in non-melanoma skin cancer development. We have previously shown that HPV8 transgenic mice spontaneously develop papillomatous skin tumors. Histology revealed epidermal hyperplasia, acanthosis and hypergranulosis and in some cases squamous cell carcinomas (SCC). Zymographic and immunoblot analysis of normal skin extracts identified increased amounts of matrix metalloproteinase (MMP)-9, MMP-13 and MT1-MMP in HPV8-positive mice compared with HPV8-negative animals. In situ gelatin zymography of tumor specimens displayed a strong proteolytic activity in papillomas, and SCC putatively attributed to the increased amounts of activated MMP-9 found in tissue extracts. In addition, immunoblot analysis revealed increased amounts of active MMP-13 and MT1-MMP in tumor extracts as compared with control extracts. Immunohistochemical stainings of SCC specimens depicted MMP-13 to be specifically expressed in stromal fibroblasts neighboring the tumor islands, whereas MT1-MMP was detected both in tumor cells and in stromal cells. Taken together, these results implicate a role for MMPs in the development of HPV8-induced cutaneous tumors.     

Depletion of cell surface CD44 in nonmelanoma skin tumours is associated with increased expression of matrix metalloproteinase 7

Background  Expression of matrix metalloproteinase (MMP)-7 and MMP-9 is low in the normal epidermis and is induced by physiological processes such as wound healing, but also malignant transformation of epidermal cells. The activity of both MMPs has been associated with the hyaluronan (HA) receptor CD44. We previously reported that the levels of CD44 and HA differ between the two types of epidermal tumours, basal (BCC) and squamous cell carcinoma (SCC), as well as between different grades of SCC.
Objectives  To investigate if the immunostaining patterns of MMP-7 and MMP-9 correlate to those of CD44 and HA in BCC and SCC.
Methods  Paraffin sections from 71 BCCs, 21 in situ SCCs and 27 SCCs were immunostained for MMP-7 and -9.
Results  Positive immunostaining for MMP-7 and MMP-9 was found in tumour cells of both BCC and SCC, while the staining intensity tended to be stronger in SCC. The staining intensity of MMP-7 was inversely correlated with that of CD44 in both tumour types. In well-differentiated SCC, the intensity of MMP-7 was generally weak, while CD44 staining was strong and homogeneously distributed. In poorly differentiated SCC, an increase in MMP-7 was seen, and the staining intensity of CD44 became weak and was locally absent. No correlation was seen between MMP-9 and CD44 or either of the two MMPs and HA.
Conclusions  Our results show that in nonmelanoma skin tumours MMP-7 and -9 are present in the tumour cells, and suggest a link between MMP-7 activity and the depletion of cell surface CD44.     

Expression of the 27-kDa heat shock protein in human epidermis and in epidermal neoplasms: an immunohistological study

The 27-kDa heat shock protein (HSP27) is a member of the small heat shock protein (HSP) family. In addition to its putative function in thermotolerance, this protein may play a part in the regulation of cell growth and differentiation. This study was conducted to assess the significance of the expression of HSP27 in human epidermis and in cutaneous neoplasms. Sixty-two biopsy samples from normal human skin and from inflammatory and neoplastic skin diseases were investigated by immuno-histochemistry on formalin-fixed paraffin-embedded tissue sections, using a monoclonal antibody specific for HSP27. In normal human epidermis, HSP2 7 is expressed in the upper epidermal layers with a cytoplasmic staining pattern. The basal cell layer does not express detectable amounts of HSP27. In hair follicles, staining is mainly confined to the outer root sheath and to the infundibular epithelium. Melanocytes, dermal fibroblasts and endothelial cells do not express detectable amounts of HSP27. HSP27 could not be detected in fetal skin until the 20th week of gestation. Tumour cells in basal and squamous cell carcinomas do not express significant amounts of HSP27. In solar keratoses, seborrhoeic keratoses, human papillomavirus (HPV)-induced hyperproliferative lesions and inflammatory skin conditions, HSP27 expression largely resembles the pattern observed in normal human skin. HSP27 is expressed in a differentiation-related pattern in normal human epidermis and hyperproliferative disorders of the epidermis. We conclude that HSP27 may be regarded as a marker of differentiation in epidermal keratinocytes. Absence of HSP27 in the upper epidermal layers may be a marker for epidermal malignancy.     

基因工程抗角蛋白抗体在正常皮肤和几种表皮增生性皮肤病皮损中的反应定位

目的　探索一株基因工程人源性抗角蛋白Fab抗体在正常皮肤及几种表皮增生性皮肤病皮损中的反应定位。方法　利用从噬菌体抗体库中筛选到的特异表达抗角蛋白Fab片段的质粒转化大肠杆菌 ,IPTG诱导表达出Fab抗体 ,纯化鉴定后用此抗体对正常皮肤及银屑病、鳞癌、基底细胞癌和脂溢性角化病皮损进行免疫组化染色。结果　正常皮肤表皮呈阴性染色 ,毛囊呈阳性染色 ,银屑病、鳞癌、基底细胞癌和脂溢性角化病皮损均呈现明显的阳性着色 ,其中银屑病皮损基底细胞层为强阳性。所有细胞染色部位均位于胞质 ,胞核未见着色 ,真皮为阴性。结论　该株人源性抗角蛋白Fab抗体主要与表皮组织结合 ,对银屑病等表皮增生性皮肤病的损害具有较高特异性。     

Keratinocyte differentiation in hyperproliferative epidermis: topical application of PPARalpha activators restores tissue homeostasis

We recently showed that topically applied PPARalpha activators promote epidermal differentiation in intact adult mouse skin. In this study we determined the effect of clofibrate and Wy-14,643, activators of PPARalpha, on hyperproliferative epidermis in hairless mice, induced either by repeated barrier abrogation (subacute model) or by essential fatty acid deficiency (chronic model). The hyperproliferative epidermis was characterized by an increased number of proliferating cells expressing proliferating cell nuclear antigen. Topical treatment with PPARalpha activators resulted in a substantial decrease in epidermal hyperplasia in both the subacute and chronic models of hyperproliferation. Following topical treatment, proliferating cell nuclear antigen-expressing cells were restricted to the basal layer, similar to normal epidermis. In hyperproliferative epidermis there was decreased expression of involucrin, profilaggrin-filaggrin, and loricrin as assayed by in situ hybridization and immunohistochemistry. Following topical treatment with PPAR activators staining for these mRNAs and proteins increased towards normal levels. Finally, topically applied clofibrate also increased apoptosis. This study demonstrates that topical PPAR activators have profound effects on epidermal gene expression in hyperproliferative skin disorders. Treatment with PPARalpha activators normalizes cell proliferation and promotes epidermal differentiation, correcting the cutaneous pathology. This study identifies PPARalpha activators as potential skin therapeutic agents.     

Specificity of Human Keratinocyte X HeLa Cell Hybrid Murine Monoclonal Antibodies

The immunofluorescent staining patterns of three differentiation-specific monoclonals (HLK3, HLK7, HLK20) that display different immunofluorescent (IF) reactivity in normal and psoriatic epidermis, were examined in basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), as well as other human normal epithelial and nonepithelial tissues. Similar staining patterns within epidermis were seen with HLK3 (intercellular) and HLK7 (perinuclear) in psoriasis, SCC, and BCC. HLK20 selectively stained BCC and SCC within epidermis and dermis, and was negative in psoriasis. The monoclonals did not react with nonepithelial tissues, but repetitively displayed positive, granular reactivity with simple epithelia and transitional epithelium. Stratified squamous epithelia showed IF staining similar to normal epidermis for all three monoclonals. These new monoclonal antibodies offer new investigative tools to study abnormalities in keratinocyte differentiation in benign and malignant hyperplastic skin diseases.     

The expression of SnoN in normal human skin and cutaneous keratinous neoplasms

Background  SnoN is a member of the ski family of proto-oncogenes. It has been revealed that SnoN plays a role in the regulation of cell growth, vertebrate development, and tumorigenesis. This study investigated the expression and significance of SnoN protein in normal human skin and in the development of seborrheic keratosis (SK), basal cell carcinoma (BCC), and squamous cell carcinoma (SCC) of the skin.
Methods  Six frozen sections of normal human skin, three of SK (acanthotic type), six of BCC, six of intraepidermal SCC (actinic keratosis, AK), and six each of poorly and well-differentiated SCC were immunohistochemically stained with a polyclonal antibody against SnoN.
Results  In normal epidermis, strong positive staining was observed in the suprabasal layers, whereas the basal cell layer was entirely unstained. Expression was observed in tumor cells with a squamoid phenotype in SK, but not in BCC. In intraepidermal SCC, although a strong signal was seen in the well-differentiated keratinocytes of the superficial epidermal cell layers, no signal was seen in the poorly differentiated atypical cells situated in the lower epidermis. In invasive SCC, a few scattered cells were positive for SnoN in the well-differentiated sample, but much larger numbers of positive cells were observed in the poorly differentiated sample.
Conclusions  On the basis of our results, it is suggested that SnoN is involved in differentiation in normal skin and benign and nonmetastatic skin tumors, but plays a proto-oncogenic role in undifferentiated SCC.     

Immunohistochemical staining for the differentiation of subungual keratoacanthoma from subungual squamous cell carcinoma

Background.  Subungual keratotic tumours are rare. The clinical and histological distinctions between subungual keratoacanthomas (SUKAs) and subungual squamous cell carcinomas (SCCs) are important, but often difficult. Adequate methods of differentiation between the two are required, both for the purpose of management and for assessment of prognosis.
Aim.  To establish the value of immunohistochemical staining patterns of proliferating cells to distinguish between SUKAs and subungual SCCs.
Methods.  In total, 20 keratotic tumours from 20 patients were examined with immunohistochemical staining techniques using bcl- 2, Ki67 and p53.
Results.  Of 20 patients, 4 had SUKAs, 5 had cutaneous KAs, 6 had subungual SCCs and 5 had cutaneous SCCs. Our results showed that a high index of staining of p53 favours the diagnosis of subungual SCC over SUKA.
Conclusion.  SUKAs do not express Ki67 strongly whereas some subungual SCCs do. Thus we conclude that immunohistochemistry for p53 and Ki67 may help distinguish between a subungual SCC and a SUKA.