Hyaline Inclusion Acanthoma.

ABSTRACT: Eosinophilic hyaline inclusions (EHIs) or globules have been reported in various cutaneous tumors including vascular lesions, myoepithelial neoplasms, and basal cell carcinoma. In basal cell carcinoma, the presence of intracytoplasmic inclusions is reportedly associated with myoepithelial differentiation. In this regard, EHI has not been conclusively documented in a cutaneous lesion of genuine squamous cell lineage without aberrant differentiation. In the current case, a biopsy from the right thigh of a 71-year-old male patient demonstrated a relatively well-demarcated intraepidermal squamous lesion featured an admixture of predominantly enlarged keratinocytes harboring distinct eccentric intracytoplasmic EHI and a smaller population of keratinocytes displaying pale cytoplasm. Cytologic atypia, mitotic activity, and inflammatory cells were not identified. The intracytoplasmic EHI stained red with Masson's trichrome and were negative with periodic-acid Schiff with and without diastase. Immunologically, the lesion was strongly and diffusely positive for various cytokeratins but negative for ubiquitin and myoepithelial markers. Only cytokeratin AE1 revealed a differential staining pattern as the suprabasal lesional cells displayed significantly stronger immunoreactivity in comparison with the adjacent normal keratinocytes. Polymerase chain reaction for low-risk and high-risk human papillomavirus was negative. Molecular studies did not reveal any mutations commonly encountered in seborrheic or lichenoid keratoses. As an analogous lesion has not previously reported in the literature, the term hyaline inclusion acanthoma is proposed for this peculiar lesion.

Malignant Clear Cell Acanthoma: Report of a Rare Case of Clear Cell Acanthoma-Like Tumor With Malignant Features.

An erythematous and moist tumor nodule on the left temple of a 92-year-old woman was biopsied and identified as a clear cell acanthoma (CCA)-like tumor with malignant cytology and high proliferation activity. This case is similar to 2 cases reported previously as atypical CCA. The authors believe that these tumors are malignant counterparts of CCA and propose to call them malignant CCA. The clinicopathologic features of the present case are described along with dermoscopic findings.

Expression of lumican in hidroacanthoma simplex and clonal-type seborrheic keratosis as a potent differential diagnostic marker.

Lumican, a member of the small leucine-rich proteoglycan family, regulates the assembly and diameter of collagen fibers in the extracellular matrix of various tissues. The lumican expression correlates with pathological conditions and the growth and metastasis of various malignancies. In cutaneous neoplasms, the lumican expression is lower in advanced-stage malignant melanomas that invade the dermis than in early-stage melanomas. Furthermore, we have recently reported that the expression pattern of lumican is different from that of actinic keratosis and the Bowen disease. Lumican is positive in the poroid cells of intraepidermal sweat ducts; therefore, we examined the expression patterns of lumican in acanthotic-type seborrheic keratosis and Pinkus-type poroma followed by clonal-type seborrheic keratosis and hidroacanthoma simplex. The neoplastic cells of acanthotic-type seborrheic keratosis exhibited positive immunostaining in only 1 of 31 cases (3.23%), whereas the poroid cells of Pinkus-type poroma exhibited positive immunoreactivity in 26 of 28 patients (92.8%). In the hidroacanthoma simplex cases, lumican was expressed in poroid cells forming intraepidermal nests in 22 of 28 patients (78.6%), whereas the neoplastic cells in most cases of clonal-type seborrheic keratosis were negative for lumican. In some seborrheic keratosis cases that were positive for lumican in neoplastic cells, lumican was observed in squamoid cells but not in basaloid cells. Therefore, it is necessary to evaluate the immunoreactivity of lumican in seborrheic keratosis and in basaloid cells. These findings suggest that lumican is a potent differential diagnostic marker that distinguishes hidroacanthoma simplex from clonal-type seborrheic keratosis.

Reticulated acanthoma with sebaceous differentiation: another sebaceous neoplasm associated with Muir-Torre syndrome?

Reticulated acanthoma with sebaceous differentiation (RASD) represents a rare benign cutaneous epithelial neoplasm with sebaceous differentiation. There has been much speculation about the relationship between RASD and Muir-Torre syndrome (MTS). We report a 53 year-old man who presented with RASD in addition to a prior history of sebaceous adenomas. Immunohistochemically, the tumour cells in the RASD and sebaceous adenomas showed a significantly reduced MSH6 protein expression, whereas there was no loss of MLH1, MSH2 and PMS2. This benign neoplasm, which can be mistaken for various other cutaneous lesions with sebaceous differentiation, deserves wider recognition for its possible association with MTS.

Clinicopathologic and immunohistochemical studies of conjunctival large cell acanthoma, epidermoid dysplasia, and squamous papilloma.

PURPOSE: To evaluate clinicopathologically and immunohistochemically a spectrum of conjunctival squamous proliferations. DESIGN: Retrospective clinicopathologic study. METHODS: One large cell acanthoma, 7 epidermoid dysplasias, and 4 squamous papillomas were evaluated with microscopy and biomarkers Ki-67, p53, epithelial membrane antigen (EMA), Ber-EP4, AE1, AE3, and 8 individual cytokeratins. Normal associated conjunctiva served as a baseline for interpretation. RESULTS: The large cell acanthoma recurred 4 times but retained its benign histopathologic features. The cells were 2-3 times larger than the keratinocytes of the normal conjunctiva and did not display atypia. Immunohistochemistry revealed a low Ki-67 proliferation index (PI) in the large cell acanthoma compared with high indices in dysplasias and papillomas. p53 was negative in the nuclei of normal epithelium while positive in all neoplasms, most intensely in the dysplasias. Immunostaining showed similar staining patterns for cytokeratins in large cell acanthoma and normal conjunctiva, except for full-thickness CK14 positivity and CK7 negativity in the lesion. Dysplasias generally lost normal CK7 expression and frequently abnormally expressed CK17. The papillomas displayed a normal cytokeratin pattern but exhibited a higher than normal PI and weak p53 positivity. CONCLUSIONS: Conjunctival large cell acanthoma is a morphologically distinctive clonal entity with clinical and immunohistochemical phenotypic characteristics denoting a dysplasia of minimal severity. Because of recurrences without invasion, it requires treatment. Dysplasias exhibited more deviant biomarker abnormalities including frequent aberrant full-thickness CK17 positivity and CK7 negativity. The absence of major cytokeratin derangements in the squamous papillomas may be of ancillary diagnostic value for lesions displaying borderline cytologic features.

Infundibulomatosis: a case report with immunohistochemical study and literature review.

Tumor of the follicular infundibulum was first described in 1961 by Mehregan and Butler in a patient presenting with multiple papules. It is more frequent, however, as an isolated lesion affecting mainly the face, neck, and upper trunk. Clinical presentation is variable, requiring histology for the diagnosis, which reveals typically a plate-like proliferation of keratinocytes in continuity with the epidermis and hair follicles; some morphological features are reminiscent of the outer root sheath of the hair follicle. A well defined network of elastic fibers surrounding the tumor is usually present using the appropriate staining and this finding is specific because it is not found in other benign follicular tumors. Multiple infundibulomas are usually sporadic and there is no apparent association with internal malignancy. The authors report the case of a 30-year-old female patient with a 5-year history of multiple small discrete hypopigmented macules and papules, scattered over the submental and submaxillary regions and anterior neck. Histopathological findings were consistent with the diagnosis of tumor of the follicular infundibulum. Immunohistochemical study was performed to further characterize the proliferation.

[Immunohistochemical study of calretinin in normal hair follicles and tumors with follicular differentiation]. / Estudio inmunohistoquímico de la calretinina en el folículo piloso normal y neoplasias con diferenciación folicular.

BACKGROUND: Selective immunostaining for calretinin labels the innermost layer of the outer root sheath of normal hair follicles, which is difficult to distinguish with hematoxylin-eosin staining. OBJECTIVE: The aim of this study was to determine whether immunohistochemistry for calretinin allows identification of cutaneous adnexal tumors with follicular differentiation towards cells of the outer root sheath. MATERIAL AND METHODS: We analyzed the staining pattern for calretinin by immunohistochemistry in 49 biopsies of cutaneous adnexal tumors with follicular differentiation. RESULTS: Fifteen biopsies corresponded to trichilemmomas/inverted follicular keratosis and had staining for calretinin in the epithelium of the most superficial areas of the lesions and in squamous eddies. Ten were trichilemmal cysts, which displayed staining of the cyst wall. Three were basal cell carcinomas with variable staining according to the type of follicular differentiation in each variant. One was a panfolliculoma that had focal staining. Two were folliculosebaceous cystic hamartomas with staining of the excretory duct of the sebaceous glands. Two pilomatricomas and 3 proliferative trichilemmal tumors had positive staining in the cellular layers close to the lumen of the cystic structures. Nine trichoblastomas/trichoepitheliomas, 2 infundibular cysts, 1 dilated pore of Winer, and 2 acanthomas of the follicular sheath were negative for calretinin. CONCLUSION: Immunohistochemistry for calretinin allows identification of cutaneous adnexal tumors of the hair follicle or a component of the follicle with differentiation towards cells of the outer root sheath.

Cutaneous clear cell squamous cell carcinoma in situ : clinical, histological and immunohistochemical characterization.

BACKGROUND: Clear cell squamous cell carcinoma in situ (SCCIS) has not been defined in the literature with respect to its clinical, histological, and immunohistochemical features. METHODS: Nearly 1500 consecutive cases of SCCIS were assessed for percent clear cell change. The clinical features of all SCCIS with >or=10% clear cell change, including age, sex and site distribution, were compared with classical SCCIS using chi-square analysis. PAS special staining and immunohistochemical analysis with 11 cell markers were performed to characterize the clear cell of origin. RESULTS: Eighty SCCIS cases with a spectrum of clear cell change of >or=10% were identified. Six cases with >or=80% clear cells were defined as clear cell SCCIS. The clinical features of the cases did not vary significantly from classical SCCIS. Antibodies labeling outer root sheath (ORS) cells also labeled clear cells in the cases and included K8.12 (labeling CK13 and CK16), cellular retinoic acid binding protein II, CAM 5.2 and CK15. Antibodies that did not label ORS cells, but did label eccrine glands (CK7 and CK18) or sebocytes (EMA), also did not label the cases. CONCLUSION: Clear cell change in SCCIS is part of a spectrum which displays ORS differentiation.

Giant clear-cell acanthoma with keratoacanthoma-like changes: a case report.

Clear cell acanthoma is a benign epidermal lesion with a variable clinical appearance and distinct histopathology features. Although, it is considered an entirely benign entity, few case reports describe unusual or atypical variants of clear cell acanthoma. We observed a case of a large clear cell acanthoma that also has features of a keratoacanthoma.