Two cases of clear cell acanthoma: an immunohistochemical study

Clear Cell Acanthoma: A Review of Clinical and Histologic Variants

Degos and Civatte first described clear cell acanthoma (CCA) in 1962 and later in a review article found that, in most instances, the lesion was a solitary red-brown dome-shaped papule that involved the distal lower extremity. The first morphologic variant of CCA was reported as a "giant form of the acanthoma of Degos" which measured 45 × 40 mm, about twice the size of the largest CCA documented earlier. Since then, many variants of CCA have been described, including polypoid, pigmented and atypical. Herein, we describe a new variant of CCA and add another example of the polypoid variant to the literature. The new variant exhibits cellular features of trichilemmoma but architecturally differs from it. We also attempt to broaden the list of CCA variants summarized by Tempark and Shwayder by adding ours and a few more examples of CCA. The new variants of CCA include verrucous, linear, subungual and trichilemmal.

Pale (Clear) Cell Acanthoma of the Palate

Clear cell acanthoma (CCA), also known as pale cell acanthoma, represents a rare benign epidermal tumor with strong predilection for the lower extremities of middle-aged individuals and no frank gender preference. The etiology of CCA is poorly understood, although a localized psoriasiform reaction is favored. Herein, we report on the clinicopathologic and immunohistochemical features, and HPV status of an apparent example of oral CCA. A 58-year-old female presented with a well-circumscribed, asymptomatic, exophytic, sessile and erythematous nodule of the right hard palate, measuring 0.7 cm in greatest dimension. Microscopically, the lesion featured parakeratosis and acanthosis with neutrophilic microabscesses and broad elongated rete pegs. In areas, spinous epithelial cells exhibited pale or clear cytoplasm without nuclear pleomorphism, mitoses or cytologic atypia. The supporting connective tissue revealed mild chronic inflammation with few scattered neutrophils and numerous capillary vessels. PAS histochemical stain with and without diastase disclosed the presence of cytoplasmic glycogen in the pale cells. The majority of glycogen-rich epithelial cells stained strongly for EMA and were negative for D2-40. Ki-67 immunostaining was confined only to the basal cell layer of the epithelium. A diagnosis of CCA was rendered. The lesion was negative for human papillomavirus (HPV) infection, as assessed by HPV-DNA PCR using the MY09/11 primers for the L1 conserved region, thus HPV infection does not appear to contribute to the pathogenesis of oral CCA. In conclusion, we report an intraoral example of CCA in order to raise awareness about this entity.

Clear cell acanthoma with changes of eccrine syringofibroadenoma: reactive change or clue to etiology?

We observed two patients with solitary lesions showing features of clear cell acanthoma with underlying eccrine syringofibroadenoma-like changes. The pathogenesis of these entities has been debated since their original descriptions, with most recent literature suggesting that both may represent reactive phenomena rather than true neoplasms. Our observation prompted us to perform a retrospective review of clear cell acanthoma cases to determine the frequency of such associated eccrine syringofibroadenoma changes. Of 47 examined cases of clear cell acanthoma, 9 (19%) showed associated changes of eccrine syringofibroadenoma. Immunohistochemical evaluation performed on a subset of cases identified similar but slightly divergent differentiation patterns within the lesions. While epithelial membrane antigen and PAS expression were similar in both components (although slightly different in intensity), the regions resembling eccrine syringofibroadenoma displayed additional immunoreactivities, supporting the presence of two distinct components. We have found that the concurrence of clear cell acanthoma with syringofibroadenomatous changes is more frequent than generally appreciated and suggest that these entities may share derivation from the eccrine apparatus.

Clear cell acanthoma

Clear cell acanthoma (CCA), is an asymptomatic benign lesion of unknown origin and aetiology, which typically presents as a red to brown, dome-shaped papule on the leg. We discuss the case of a patient with an irregular plaque of hypopigmented papules whose diagnosis of CCA was only made by biopsy, and review the characteristic presentation, uncommon variants, locations and associated conditions of this lesion. The diagnosis is based on histopathology and/or immunohistochemistry, but the variable clinical presentation may make diagnosis difficult. The differential diagnosis includes skin tumours and inflammatory and pigmentary dermatoses. The lesions do not regress spontaneously, and excisional removal is the preferred treatment.

Clear-cell acanthoma versus acanthosis: a psoriasiform reaction pattern lacking tricholemmal differentiation

Clear-cell acanthoma (CCA) has been reported to be a benign epidermal neoplasm; however, several authors have suggested alternative differentiation as well as other nosologic categories, including a reactive dermatosis. Fourteen CCAs, ten tricholemmomas, and seven cases of psoriasis were reviewed with conventional microscopy, periodic acid-Schiff stains, and immunohistochemical stains. Twelve of fourteen (86%) CCAs were associated with underlying or adjacent conditions. The CCAs stained immunohistochemically in a pattern similar to normal epidermis and psoriasis. Tricholemmomas stained in a distinctly different pattern with MNF116 and NGFR/p75. These cases demonstrate CCA in settings that reflect chronic inflammation, primarily scars and stasis dermatitis, and with an immunophenotype that parallels psoriasis. These findings support the contention that CCA does not show outer follicular sheath (tricholemmal) differentiation. Furthermore, these cases lend additional support to the contention that CCA represents a psoriasiform reaction pattern, which, in appropriately taken biopsies, usually has a demonstrable associated condition. Nonetheless, the precise nosology of this phenomenon has yet to be elucidated completely.

Expression of keratinocyte growth factor and its receptor in clear cell acanthoma

The aetiopathogenic mechanism underlying clear cell acanthoma (CCA) is not completely clear and it has been postulated that CCA and psoriasis may have a similar pathogenesis because of the common features shared by the two diseases. As it has been recently demonstrated that in psoriatic lesions the paracrine epithelial growth factors [keratinocyte growth factor (KGF)/fibroblast growth factor (FGF)-7 and FGF-10] are involved in promoting and sustaining the keratinocyte hyperproliferation, the aim of this study was to analyse the expression of KGF on CCA lesions and to search for a role of this growth factor in CCA pathogenesis. Immunohistochemical analysis showed an up-modulation of KGF in CCA, although the immunostaining was variable among the different samples collected. Positive immunoreactivity for KGF was detected mainly on dermal areas where the inflammatory infiltrate was more pronounced suggesting a relationship between lymphocyte activation and KGF up-modulation. Real-time quantitative RT-PCR assay performed on mRNA extracted from formalin-fixed paraffin-embedded CCA and normal skin (NS) samples further demonstrated the overexpression of the KGF/FGF-7 gene in all CCA samples compared with NS. Moreover, the evaluation by immunohistochemistry of KGF receptor distribution, the high-affinity tyrosine kinase receptor for KGF, showed a down-modulation of this receptor, as previously reported in the presence of increased levels of KGF. Taken together these results suggest the inflammatory nature of CCA and further support the hypothesis that this disease may represent, like psoriasis, an inflammatory dermatosis in which KGF up-modulation may be responsible for keratinocyte hyperproliferation and may represent a new common feature of both diseases.

Follicular stem cell carcinoma: histologic, immunohistochemical, ultrastructural, and clinical characterization in 30 dogs

Diagnostic records of 30 primary and one metastatic follicular stem cell carcinomas in 30 dogs were reviewed. Neoplastic cells had a clear cytoplasm and formed lobules and nests surrounded by a basement membrane. Trichoepitheliomatous and apocrine differentiations were noted in 22 of 30 (73%) and 21 of 30 (70%) primary tumors, respectively. Glycogen was present in 20 of 20 (100%) tumors tested, suggesting tricholemmal differentiation. Antibodies against AE1/AE3 cytokeratin, vimentin, and melanA/MART1 stained 29 of 30 (97%), 29 of 30 (97%), and 12 of 27 (44%) primary tumors, respectively. Small amounts of melanin were identified in 14 primary tumors, either on the hematoxylin and eosin-stained section (n = 6), or on the Fontana-stained section (n = 8 of 14). Ultrastructural features of neoplastic cells included cell junction complexes, swollen mitochondria, neuroendocrine-like granules, and intracytoplasmic non-membrane-bound accumulation of proteinaceous material. Features of this neoplasm are consistent with a follicular stem cell origin. Follow-up information was available for eight dogs. Metastases developed in the draining lymph node at the time of excision of the primary tumor (n = 1) or subsequently (n = 3).

Clear cell acanthoma developing in epidermal nevus

A 33-year-old Japanese woman presented with a black papule on a pigmented lesion which had been on her right thigh since her early childhood. A hematoxylin-eosin-stained section revealed a sharply demarcated, acanthotic epidermis composed of enlarged clear cells, which stained positively for epithelial membrane antigen and negatively for carcinoembryonic antigen. With antikeratin antibodies, the tumor cells stained for AE1 and AE3, but did not stain for CAM5.2. They contained abundant glycogen. Histologically, we diagnosed the case as a clear cell acanthoma which developed in the pre-existing epidermal nevus. This is the second such case in the literature.

Squamous cell carcinoma in situ arising within clear cell acanthoma

BACKGROUND

A brief discussion of the subject.

OBJECTIVE

The purpose of the work to be described.

METHODS

How the work was performed.

RESULTS

The outcome of the work.

CONCLUSION

The conclusion that can be reached based on the work described.

Cystic clear cell acanthoma

An histologically typical clear cell acanthoma was identified forming a cystic structure. The finding of clear cell acanthoma within a cyst is histologically unique.

Disseminated eruptive clear cell acanthoma--a case report with review of the literature

Clear cell acanthoma (CCA) is a benign epidermal tumour with distinctive and uniform clinical and histological features. Although solitary lesions are the rule, some cases of multiple CCA, rarely with more than 10 lesions, have been previously reported. Only 22 cases of multiple CCA have been described in the English literature to date. A healthy 32-year-old woman is reported, with approximately 400 asymptomatic rounded papules, on the upper and lower extremities. Multiple skin biopsies showed the typical histological pictures of CCA. This case appears unusual because of the presence of numerous lesions scattered on the upper and lower extremities. For this reason it could be classified as disseminated eruptive CCA.

Atypical clear cell acanthoma

Two cases of clear cell acanthoma (CCA) with marked signs of cellular atypia and mitotic figures are reported. Although the nature of CCA is not completely understood, it is considered to be a benign epithelial tumor. Our cases show that these lesions can develop malignant features.

Lectin-binding sites in clear cell acanthoma

Lectin-binding sites in clear cell acanthoma (CCA) were studied using an avidin-biotin complex (ABC) with 9 lectins. Formaldehyde-fixed, paraffin-embedded sections of 7 CCA lesions were employed. Positive stainings, similar to those seen in normal epidermis, were observed on the cell surface in CCA with Ricinus communis agglutinin I (RCA-I), Ricinus communis agglutinin II (RCA-II), and wheat germ agglutinin (WGA). Reduced reactivities were observed with Concanavalin A (ConA) and peanut agglutinin (PNA) in CCA. In some areas of CCA lesions, faint stainings were seen with Ulex europaeus agglutinin I (UEA-I). Capability of staining with soybean agglutinin (SBA) was completely lost in the lesions. With Bandeiraea simplicifolia agglutinin II (BSA-II), cytoplasmic stain was seen in a part of upper and spinous layers in CCA lesions. Dolichos biflorus agglutinin (DBA) did not bind to either CCA or normal epidermis. These results indicate that the lectin-binding sites of proliferating cells of CCA resemble those of epidermal keratinocytes and suggest that CCA is a tumor of epidermal origin.