Keratoacanthoma and other types of squamous cell carcinoma with crateriform architecture: Classification and identification

Aberrant p16, p53 and Ki-67 immunohistochemistry staining patterns can distinguish solitary keratoacanthoma from cutaneous squamous cell carcinoma

Keratoacanthoma (KA) is widely considered a benign, usually self-resolving, neoplasm distinct from cutaneous squamous cell carcinoma (cSCC), while some consider KA to be indistinguishable from cSCC. Published studies indicate utility for p16, p53, Ki-67 immunostaining and elastic van Gieson (EVG) in the assessment of KA and cSCC. We compared clinical features and staining patterns for p16, p53, Ki-67 and EVG in fully excised KA, cSCC with KA-like features (cSCC-KAL) and other cSCC (cSCC-OTHER). Significant differences between KA, cSCC-KAL and cSCC-OTHER were found for head and neck location (20%, 86%, 84%), and duration <5 months (95%, 63%, 36%). KA shows both a mosaic pattern for p16 (>25-90% of neoplasm area) and peripheral graded pattern for p53 (up to 50% moderate and strong nuclear staining) in 92% compared with 0% of cSCC-KAL and 0% of cSCC-OTHER. In contrast, a highly aberrant pattern (usually null) for one or both p16 and p53, was present in 0% of KA, 83.8% of cSCC-KAL and 90.9% of cSCC-OTHER. Abnormal distribution of Ki-67 beyond the peripheral 1-3 cells was uncommon in KA (4.2%) and common in cSCC-KAL (67.6%) and cSCC-OTHER (88.4%). Moderate to striking entrapment of elastic and collagen fibres was present in the majority of KA (84%), cSCC-KAL (81%) and cSCC-OTHER (65%). KA are clinically distinct neoplasms typically of short duration occurring preferentially outside the head and neck and generally lacking aberrations of p16, p53 and Ki-67, compared with cSCC that have high rates of aberrant or highly aberrant p16, p53 and Ki-67, but EVG lacked specificity.

Histological Variants of Squamous and Basal Cell Carcinoma in Squamates and Chelonians: A Comprehensive Classification

In the present study, the histological characteristics of squamous cell carcinomas (SCCs) and basal cell carcinomas (BCCs) obtained from 22 squamate and 13 chelonian species were retrospectively evaluated. While the examined tissues were originally diagnosed as 28 SCCs and 7 BCCs based on histological evaluation by a specialty diagnostic service, eight SCCs could be re-classified as BCCs and three SCCs proved to be non-neoplastic lesions. In addition, all SCCs and BCCs were classified into distinct histological variants. The SCCs could be categorized as one SCC in situ, three moderately differentiated SCCs, seven well-differentiated SCCs, and six keratoacanthomas. BCCs were classified as five solid BCCs, four infiltrating BCCs, five keratotic BCCs, and one basosquamous cell carcinoma. In addition, the present study reports the occurrence of BCCs in seven reptile species for the first time. In contrast to what has been documented in humans, IHC staining with the commercially available epithelial membrane antigen and epithelial antigen clone Ber-EP4 does not allow differentiation of SCCs from BCCs in reptiles, while cyclooxygenase-2 and E-cadherin staining seem to have discriminating potential. Although the gross pathological features of the examined SCCs and BCCs were highly similar, each tumor could be unequivocally assigned to a distinct histological variant according to the observed histological characteristics. Based on the results of this study, a histopathological classification for SCCs and BCCs is proposed, allowing accurate identification and differentiation of SCCs and BCCs and their histological variants in the examined reptile species. Presumably, BCCs are severely underdiagnosed in squamates and chelonians.

What Is a Solitary Keratoacanthoma? A Benign Follicular Neoplasm, Frequently Associated with Squamous Cell Carcinoma

We present histopathological criteria for diagnosing keratoacanthoma (KA). In KA, four histological stages are recognized, which are the early/proliferative stage, well-developed stage, regressing stage and regressed stage. In diagnosing KA, we emphasize that KA consists of the proliferation of enlarged pale pink cells with ground glass-like cytoplasm without nuclear atypia, other than crateriform architecture. KA sometimes exhibits malignant transformation within the lesions. We describe the characteristics of benign and malignant epithelial crateriform tumors that should be differentiated from KA. We also present the data of histopathological diagnosis of lesions clinically diagnosed as KA, its natural course and related lesions after partial biopsy, and incidence of crateriform epithelial neoplasms. Based on these data, we recommend complete excision of the lesion when KA is clinically suspected, especially when the lesion is located on a sun-exposed area of an elderly patient. If complete excision is impossible, partial excision of a sufficient specimen with intact architecture is required. In such a case, however, careful investigation after biopsy will be needed, even if the histopathological diagnosis is KA, because there is some possibility that a conventional SCC lesion remains in the residual tissue.

A clinical and biological review of keratoacanthoma

Keratoacanthoma (KA) is a common skin tumour that remains controversial regarding classification, epidemiology, diagnosis, prognosis and management. Classically, a KA manifests as a rapidly growing, well-differentiated, squamoid lesion with a predilection for sun-exposed sites in elderly people and a tendency to spontaneously regress. Historically, KAs have been considered a variant of cutaneous squamous cell carcinoma (cSCC) and are often reported as KA-type cSCC. However, the penchant for regression has led many to categorize KAs as biologically benign tumours with distinct pathophysiological mechanisms from malignant cSCC. The clinical and histopathological similarities between KA and cSCC, particularly the well-differentiated variant of cSCC, have made definitive differentiation difficult or impossible in many cases. The ambiguity between entities has led to the general recommendation for surgical excision of KAs to ensure a potentially malignant cSCC is not left untreated. This current standard creates unnecessary surgical morbidity and financial strain for patients, especially the at-risk elderly population. There have been no reports of death from a definitive KA to date, while cSCC has an approximate mortality rate of 1·5%. Reliably distinguishing cSCC from KA would shift management strategies for KAs towards less-invasive treatment modalities, prevent unnecessary surgical morbidity, and likely reduce associated healthcare costs. Herein, we review the pathophysiology and clinical characteristics of KA, and conclude on the balance of current evidence that KA is a benign lesion and distinct from cSCC.

Differences in the mitochondrial microsatellite instability of Keratoacanthoma and cutaneous squamous cell carcinoma

Keratoacanthoma (KA) is a common cutaneous neoplasm which often resembles typical squamous cell carcinoma (SCC) in both its clinical and historical presentation. Several studies have attempted to identify methods for distinguishing between KA and SCC, however, none of these have proven to play any obvious roles in these tumors. Given this we went on to evaluate mitochondrial microsatellite instability (mtMSI) in KA and SCC in an effort to understand these tumors better. DNA was isolated from paired normal and tumoral tissues donated by 57 KA patients and 43 SCC patients. MtMSI was then analyzed using eight microsatellite markers and was observed in 2 (3.5%) of the 57 KA patients and 8 (18.6%) of the 43 SCC patients, respectively. MtMSI was also shown to affect different locations depending on tumor type. In KA patients, mtMSI was detected at mitochondrial D514 D-loop and presented with (CA) n repeats, in contrast, all of the SCC patient experienced mtMSI at the D310 with (C)n repeats of the D-loop region. These differences in location were found to be significant, which may support the hypothesis that KA and SCC have different pathogenetic pathways. Our results also suggest that mtMSI may be a candidate for developing novel differential diagnostic methods for KA and SCC.

Keratoacanthoma: Update on the Debate

ABSTRACT

Keratoacanthoma (KA) is a cutaneous tumor with a biphasic pattern of growth. A rapidly growing phase is usually followed by involution. KA occurs on sun-damaged skin. There are many listed causative associations, which include some therapeutic agents. Debate continues as to whether KA is a variant of squamous carcinoma (SCC) or a separate entity. Reporting of KA versus SCC is markedly inconsistent. Reasons for inconsistency include overlapping microscopic criteria, variants of KA with more aggressive features, and possibly medicolegal concerns. Genetic studies have shown some differences between the 2 entities. Activation of apoptotic pathways has been demonstrated in KA. Genetic studies have shown a possible role of human polyomavirus 6 in the pathogenesis of at least some KAs. Given that some cases of KA have components that behave as conventional SCCs, KA can be considered as a low-grade variant of SCC with some genetic differences.

A giant keratoacanthoma of the cheek

Keratoacanthoma (KA) is a cutaneous tumor arising on sun-exposed skin and characterized by self-limiting growth and involution. We reported a case of a 92-year-old man presented a 4.5x3.5 cm nodular lesion with a central keratin-filled crater on his left cheek. We performed surgical excision and histopathological examination revealed a keratoacanthoma with perineural invasion. A close follow-up was carried out. (www.actabiomedica.it).

Myriad facades of keratocanthoma: Benignity VS malignancy

Keratoacanthoma (KA) is a self-limiting benign epithelial neoplasm. It occurs predominantly on sun-exposed areas of the body and is believed to arise from hair follicle. It shows a unique behavior in being clinically benign and microscopically malignant. Earlier it was considered as a pseudomalignant lesion but now it is believed to be pseudobenign in nature. The most common concern is related to its nosological position at the border of malignancy and benignity. We hereby report a rare case of keratoacanthomatous type of squamous cell carcinoma in an elderly female showing aggressive nature of the lesion. The various terminologies used for KA in the past have also been tabulated.

Keratoacanthoma en plaque/nodule: A brief report of the clinicopathological features of five cases

Keratoacanthoma (KA) is characterized by exoendophytic growth with a central keratin-filled crater, representing the crateriform architecture. We herein report five rare cases of KA without a central keratin-filled crater. These KA cases histopathologically showed that one or a few infundibular structures/isthmic lobules had their own open keratotic pores on the surface without a common merged keratotic plug/horn, clinically representing verrucous (keratotic) plaque/nodule, namely, "KA en plaque/nodule". KA rarely but on occasion does show verrucous plaque (or nodular) lesions without a central keratin-filled crater, as the notion that KA invariably shows crateriform architecture is nonsensical.

Cytokeratin 17 and Ki-67: Immunohistochemical markers for the differential diagnosis of keratoacanthoma and squamous cell carcinoma

The clinical and histopathological distinction between keratoacanthoma (KA) and squamous cell carcinoma (SCC) is essential, but frequently difficult to make. The utility of CK17 and Ki-67 expression in distinguishing between KA and SCC was investigated. Immunohistochemical staining patterns for CK17 and Ki-67 were evaluated in 24 KA and 27 SCC cases. The pattern of staining was evaluated as central, peripheral or diffuse, according to the basal/peripheral and suprabasal/central cell staining of tumor lobules. The sensitivity and specificity of the central CK17 staining pattern in the identification of KA were 92 and 70%, respectively. Additionally, the sensitivity and specificity of the diffuse Ki-67 staining pattern in the identification of SCC were 81 and 100%, respectively. The results of the present study suggest that a diffuse Ki-67 staining pattern may be used to diagnose SCC, while a central CK17 staining pattern indicates KA. However, the KA-like SCC cases exhibited mixed patterns, which limits the effectiveness of these markers.

Histopathologic features of multiple cutaneous squamous cell carcinomas of the lower extremity

Recent studies suggest cutaneous squamous cell carcinomas (SCCs) of the leg, particularly those occurring multiply in sun exposed skin of nonimmunosuppressed women, are a distinct clinical subtype. There are few reports of the histopathologic features of this subtype. A retrospective chart review of 4 patients with multiple SCCs on the leg was performed and a total of 35 biopsies from the legs examined. Histopathologically, the tumors lacked adjacent actinic keratosis (AK) and often had adjacent basaloid retiform proliferations. Most lesions (all but one) were well differentiated and about 40% could be classified histopathologically as keratoacanthoma. Perineural invasion was absent in all but one case. Using the American Joint Committee on Cancer (AJCC) staging criteria for SCC, 21 tumors were Stage I, and 9 Stage II. During 7-10 years of follow-up, no recurrence or metastasis occurred. Patients with multiple SCCs on the lower extremities can have a range of histopathologic features, from keratoacanthoma-like to well-differentiated SCC.

Keratoacanthoma (KA): An update and review

Keratoacanthoma (KA) is a common but underreported tumor of the skin. Two striking features of KA are its clinical behavior with spontaneous regression after rapid growth and its nosological position on the border between benignity and malignancy. We review current knowledge on the clinical, histopathological, and dermoscopic features of KA to ensure a proper diagnosis and describe its variants, including different types of multiple KAs. We highlight current concepts of KA ethiopathogenesis with special emphasis on the genetic background of multiple familial KA, the role of Wnt signaling pathway, and induction of KA by BRAF inhibitors and procedures of esthetic dermatology. Finally, treatment strategies are presented with surgical excision as a first option, followed by other modalities, including intralesional chemotherapy, topical and systemic agents, lasers, cryotherapy, and photodynamic therapy.

Insulin-like growth factor 2 mRNA-binding protein-3 as a marker for distinguishing between cutaneous squamous cell carcinoma and keratoacanthoma

In the histopathological diagnosis of cutaneous tumors, the differential diagnosis of squamous cell carcinoma (SCC) with crateriform architecture and keratoacanthoma (KA) is often difficult so an accurate understanding of the biological features and the identification of reliable markers of SCC and KA are crucial issues. Insulin-like growth factor 2 mRNA-binding protein-3 (IGF2BP3, also known as IMP3) is thought of as a bona fide oncofetal protein, which is overexpressed and is involved in cell proliferation, migration, and invasion in several kinds of tumors. However, the role of IMP3 in cutaneous SCC and KA has not been well studied. Therefore, we focused on studying the biological functions of IMP3 in SCC and KA. In human skin SCC cell lines, HSC-1 and HSC-5, and the human keratinocyte cell line, HaCaT, IMP3 mRNA levels were significantly higher than that of normal human skin. The knockdown of IMP3 expression reduced the proliferation of HSC-1, and significantly reduced invasion by HSC-1 and HSC-5. In contrast, the knockdown of IMP3 did not significantly affect invasion by HaCaT cells. In immunohistochemical studies of SCC and KA tissues, the Ki-67 labeling index (LI) of the suprabasal cell layer was significantly higher in SCC, compared with KA tissues and the tumor-free margin (TFM) adjacent to SCC and KA. Most SCC tissues stained strongly positive for IMP3, but KA tissues and TFM were mostly negative for IMP3. The Ki-67 LI of the IMP3-positive group was significantly higher than that of the IMP3-negative group in the suprabasal cell layer of SCC. These results suggest that IMP3 plays an important role in proliferation and, more significantly, in the invasion of SCC, and may be a suitable marker for the histopathological diagnosis of SCC with a crateriform architecture and KA. Furthermore, IMP3 may potentially be a new therapeutic target for SCC.

Crater/ulcerated form of infundibular squamous cell carcinoma: A possible distinct entity as a malignant (or high-grade) counterpart to keratoacanthoma

Follicular squamous cell carcinoma (SCC) with infundibular differentiation includes the common and crater forms of infundibular SCC. We previously considered the crater/ulcerated infundibular SCC to be a progressive condition of the common form and histopathologically studied an additional five cases of the crater/ulcerated infundibular SCC, the results of which suggested the following characteristic histopathological features and possible developmental process in this type of SCC: (i) a considerable number of continuous hyperplastic follicular infundibula, which may develop at the beginning of the disease; (ii) hyperplastic infundibula exhibiting an abrupt or gradual transition to the SCC component, which frequently change relative to the neoplastic infundibular canal; and (iii) the presence of multiple sites of branching of the neoplastic infundibular canals and/or complete involvement of large cysts in the neoplastic process over the center of the lesion, resulting in ulceration. Based on these histopathological findings, we considered that crater/ulcerated infundibular SCC involve a considerable number of continuous follicular infundibula from the start, although some cases may develop from the common form. We also emphasize the possible aggressive biological behavior of the crater/ulcerated form. Keratoacanthoma (KA) is a unique, benign or borderline malignant neoplasm exhibiting follicular (infundibular/isthmic) differentiation characterized by the involvement of continuous follicular infundibula in multiples. From this standpoint, we consider that crater/ulcerated infundibular SCC is possibly related to KA in terms of histogenesis and is a malignant (or high-grade) counterpart of KA.

Keratoacanthoma versus invasive squamous cell carcinoma: a comparison of dermatoscopic vascular features in 510 cases

Introduction:

Keratoacanthoma (KA) and invasive squamous cell carcinoma (SCC) are keratinocytic tumors displaying vascular features, imaged using dermatoscopy.

Objective:

Compare the dermatoscopy vascular features of KA to SCC.

Methods:

This prospective study examined consecutive cases of 100 KA and 410 invasive SCC in a single private practice in Sydney, Australia. Vascular features were recorded in vivo direct from patients using a non-polarized Delta 20 Heine dermatoscope. These vascular features were: linear, branching, serpentine, hairpin, glomerular and dot vessels, the presence or absence of large diameter tumor vessels, vessel presence in central verses peripheral tumor areas and tumor pink areas in different proportions. Following full excision, all cases were submitted for histopathologic diagnosis.

Results:

Branching vessels were the only vessel morphology that varied, with a significant incidence in KA (25.0%), compared to SCC (10.7%), P < 0.01. Large vessels were identified in 20.0% of KA, compared to 12.4% in SCC, P = 0.05. No vessels were observed in the central tumor areas in 43.4 % of KA compared to 58.0% of SCC, P = 0.01. Other data comparing the central versus peripheral tumor areas for vessels present did not reveal any distinctive associations. There were no significant differences between KA and SCC when reviewing the selected proportions of pink within the tumor.

Limitations:

The vascular features may be confounded by tumor depth in KA. Polarized dermatoscopy may not produce the same findings.

Conclusion:

This study found branching vessels to have a higher incidence in KA compared to invasive SCC. Although not statistically significant, large diameter vessels were also more frequent in KA. Proportions of pink within the tumor or central verses peripheral tumor vessel distribution were not useful diagnostic features separating KA from SCC using dermatoscopy.

Skin cancer - an overview for dentists

Skin cancer is common and an increasing problem in the UK. It frequently occurs on the head and neck skin. A significant proportion of the adult population in the UK visits the dentist each year, thus making dental practitioners ideally placed to identify suspicious lesions, which could be skin cancer, as part of their routine extra-oral examination. These patients can then be referred on to hospital or their GP for further management. The dentist can also give advice on risk factors and self-monitoring to patients. This paper aims to describe the risk factors, pathology, presentation and treatments for the three most common forms of skin cancer - basal and squamous cell carcinomas, and malignant melanoma, to give the dental practitioner the knowledge and confidence to examine for and identify these skin cancers.

The changes in the expression levels of follicular markers in keratoacanthoma depend on the stage: keratoacanthoma is a follicular neoplasm exhibiting infundibular/isthmic differentiation without expression of CK15

BACKGROUND

Although the precise etiology of keratoacanthoma (KA) is unknown, KA is generally assumed to differentiate toward hair follicles based on previous studies of experimental carcinogenesis.

METHODS

We performed a comprehensive immunohistochemical study of various follicular markers in all stages of KA. A total of 67 tumors, including 16 early or proliferative stage lesions, 43 well-developed stage lesions, five regressing stage lesions and three regressed stage lesions, were subjected to the analysis.

RESULTS

CK15 (clone C8/144B), CK19 and CD34 were not expressed at any stage. CK1, CK10, CK16, CK17, CK15 (clone LHK15) and calretinin showed dynamic changes in their expression in KA depending on the stage.

CONCLUSIONS

KA is a follicular neoplasm with infundibular/isthmic (upper segmental region of hair follicles) differentiation. It is considered that early or proliferative stage tumors show keratin-filled invaginations with infundibular differentiation and gradual isthmic differentiation. Well-developed examples of KA generally show isthmic differentiation in the whole lesions. The regressed stage KAs lose the features of this type of follicular differentiation and show epidermal characteristics. No expression of CK15 (clone C8/144B) was observed in KAs, although this finding is insufficient to completely rule out the correlation between the regression of KA and the hair follicle cycle.