Clear cell papulosis: report of three cases of a newly recognized disease

Clear Cell Proliferations of the Skin: A Histopathologic Review

ABSTRACT

Cutaneous clear cell proliferations encompass a heterogenous group of several primary cutaneous neoplasms and metastatic tumors with different histogenesis. Many of these clear cell proliferations may seem strikingly similar under the microscope resulting in challenging diagnosis. In many of these clear cell lesions, the reason for the clear or pale appearance of proliferating cells is unknown, whereas in other ones, this clear cell appearance is due to intracytoplasmic accumulation of glycogen, mucin, or lipid. Artifacts of tissue processing and degenerative phenomenon may also be responsible for the clear cell appearance of proliferating cells. Awareness of the histopathologic findings as well as histochemical and immunohistochemical techniques are crucial to the accurate diagnosis. This review details the histopathologic features of clear cell cutaneous proliferations, classifying them according their type of differentiation and paying special attention to the histopathologic differential diagnosis among them.

Extramammary Paget disease of the vulva

Extramammary Paget disease (EMPD) is a rare neoplasm with uncertain histogenesis, usually presenting in the anogenital area, most commonly in the vulva. The disease is characterized by slow grow and high recurrence rates. This article reviews the epidemiological, clinical, morphological, genetic and treatment features of EMPD of the vulva reported in recent years.

Clear cell papulosis: Dermatoscopic findings and literature review

Clear cell papulosis is a rare skin condition that predominantly develops in patients of Asian background during their early childhood. We present a new case of clear cell papulosis of a 1-year-old Thai girl presented with multiple hypopigmented macules and papules on the lower abdomen and pubic area for 3 months and also review the previous 41 cases published in the literature since 1987. Herein, for the first time, we report the dermatoscopic features of clear cell papulosis that represents as depigmented homogenous structureless lesions. This would be beneficial for distinguishing clear cell papulosis from its differential diagnoses.

Clear-cell papulosis: a rare entity that may be misconstrued pathologically as normal skin

We describe a case of multiple, discrete, hypopigmented macules in the suprapubic and axillary region in a healthy 3-year-old girl. The lesions first appeared at approximately 9 months of age and increased in number over time. Initial histopathologic examination by an outside dermatopathologist at 1 year of age was reported as showing nonspecific histologic changes. A repeat biopsy at 3 years of age showed large intraepidermal clear cells that expressed CKAE1/CAM5.2, CK7, and BRST2. These findings are diagnostic for clear-cell papulosis, a rare condition that primarily affects children. Without great clinical and pathologic suspicion, this is a diagnosis that can often be overlooked because the histologic findings are virtually identical to those of normal skin.

Lesions of anogenital mammary-like glands: an update

Long considered to be ectopic breast tissue representing the caudal remnants of the milk ridges, anogenital mammary-like glands are nowadays thought to represent a normal constituent of the anogenital area. Lesions involving these glands, benign or malignant, epithelial or stromal manifest a striking similarity to their mammary counterparts. This review addresses the recent literature on lesions of anogenital mammary-like glands and our personal experience with various lesions related to these structures. Discussed are the normal anatomy and histology of these glands as well as the clinical presentation, histopathological and immunohistochemical features, molecular biological aspects, and differential diagnosis of various lesions involving anogenital mammary-like glands, including lactating adenoma, hidradenoma papilliferum, hidradenocarcinoma papilliferum, fibroadenomas, phyllodes tumor, pseudoangiomatous stromal hyperplasia, extramammary Paget disease, and other carcinomas. In addition, "nonspecific" epithelial or stromal changes some of which can be likened to similar changes occurring in a range of benign breast disease, including sclerosing adenosis, columnar cell lesions, ductal lesions and various metaplastic changes affecting epithelium and myoepithelium are discussed. Although lesions of anogenital mammary-like glands are often discussed in many dermatopathology textbooks in the context of cutaneous adnexal neoplasms we advocate that the best approach to the diagnosis of these lesions is to relate them to analogous well recognized lesions occurring in the breast, that is, through the eyes of a breast pathologist. This will enable their recognition, precise classification and should introduce greater uniformity in how they are reported in the literature so that more meaningful clinicopathological comparisons and correlations may be made.

Clear Cell Papulosis of the Skin: A Case Report From Singapore

Clear cell papulosis of the skin is a rare condition; to our knowledge only 12 cases have been reported. Here, we report for the first time a case of clear cell papulosis with cytokeratin 7 expression and provide a comprehensive literature review. A 16-month-old girl presented with 3 hypopigmented lesions in the pubic region that were 3 to 9 mm in diameter; 1 lesion was papular, and the other 2 were macular. A skin biopsy revealed acanthosis with a proliferation of clear cells along the basal and suprabasal layers of the epidermis occurring in small clusters and singly. The cells had round to oval regular nuclei with abundant to moderate lightly eosinophilic to clear cytoplasm and intracytoplasmic mucin. Immunostaining produced positive results for carcinoembryonic antigen, AE1/3, epithelial membrane antigen, cell adhesion molecule 5.2, and cytokeratin 7 and negative results for gross cystic fluid disease protein, S100, and HMB-45. Clear cells of clear cell papulosis are mucin-positive and S100-negative glandular-secretory epithelial cells with histogenetic features of Toker cells of nipple and Paget cells. Immunohistochemical features support an eccrine secretory cell origin because the clear cells are consistently and strongly positive for carcinoembryonic antigen, positive for cell adhesion molecule 5.2, and negative or rarely positive for gross cystic fluid disease protein.

Non-melanocytic lesions mimicking melanocytic lesions

Distinction between benign and malignant melanocytic lesions commonly represents a big challenge for the pathologist. Equally difficult is separating tumours with melanocytic lineage from those displaying other lines of differentiation. This is because benign and malignant melanocytic lesions are able to display a wide range of histological appearances that frequently closely mimic reactive and neoplastic lesions (benign and malignant). This applies to processes with almost any line of differentiation. Difficulties in differential diagnosis are mainly found in melanocytic lesions restricted to the dermis or those in which the junctional component is minimal. Although purely junctional melanocytic lesions less commonly pose a problem in differential diagnosis, they may be very problematic, especially in small biopsies. Immunohistochemistry is usually a very important aid in the differential diagnosis of mimics of melanocytic lesions but pitfalls often occur. This is particularly true when small samples are analysed and when close clinicopathological correlation is lacking. This review discusses the histological differential diagnosis of mimics of melanocytic lesions. These mimics are separated into those primarily presenting in the epidermis and those presenting in the dermis.

Clear cells of Toker in accessory nipples

BACKGROUND

Clear cells of Toker are intraepithelial cells with clear to pale staining cytoplasm and bland cytologic features found in approximately 10% of normal nipples. Toker cells have been hypothesized as a precursor of extramammary Paget's disease (EMPD), although the distribution of Toker cells outside of the nipples has not been studied. Using immunohistochemistry, we studied 20 cases of accessory nipples for the presence of Toker cells.

METHODS

A retrospective study of 20 cases of accessory nipples was performed using routine hemotoxylin and eosin staining, as well as immunohistochemical staining for CK7, CK20, EMA, and GCDFP-15.

RESULTS

Thirteen out of 20 accessory nipples (65%) demonstrated Toker cells with CK7 staining. Toker cells in six of the 13 cases were also positive for EMA. Only one case with Toker cells showed immunoreactivity for antibodies to GCDFP-15.

CONCLUSIONS

Toker cells occur outside the normal nipple epidermis in the epidermis of accessory nipples. The distribution of Toker cells along the milk line correlates with the distribution of most cases of EMPD along the milk line, especially in the groin and axillae. Further studies are necessary to define the relationship between Toker cells and EMPD.

Clear cell papulosis: an immunohistochemical study to determine histogenesis

Clear cell papulosis is a rarely described disease characterized by multiple white maculopapules. Histopathologically, diagnostic clear cells are seen mainly among the basal cells of the epidermis. The origin of the clear cells has been thought to be eccrine or apocrine secretory cells in the epidermis because of the positive immunostaining with anticytokeratin antibody AE1, carcinoembryonic antigen (CEA), epithelial membrane antigen, and gross cystic disease fluid protein-15. IKH-4 and CEA have been reported to stain the eccrine secretory cells, but not the apocrine secretory cells. On the contrary, lysozyme has been reported to stain apocrine glands, but not eccrine glands. CAM5.2 has been reported to show a positive reaction to staining in secretory cells of eccrine glands, but only occasional weak staining in the inner surface of eccrine ducts. In our study, the clear cells in the epidermis stained with IKH-4, CEA and CAM5.2, but not with lysozyme. These results suggest that the clear cells may be eccrine secretory cells.

Differential expression of mucin genes in mammary and extramammary Paget's disease

Paget's disease (PD) of the skin is characterized by intraepidermal adenocarcinoma cells, which contain clear cytoplasm and abundant mucin. Nearly all cases of mammary PD (MPD) are associated with underlying ductal carcinoma of the breast, whereas in the majority of cases of extramammary PD (EMPD) no underlying regional malignancy is identified. Mucins are high molecular weight glycoproteins produced by epithelial cells. Different mucin genes are expressed in various types of tissues such as mammary glands, intestinal mucosa, and adnexal structures of the skin. We studied the immunohistochemical expression of apomucin MUC1, MUC2, MUC5AC in MPD, and EMPD. MUC1 is commonly expressed in most cases of PD. MUC5AC is a unique mucin that is exhibited in the majority of cases of EMPD, but not in any MPD. Of the 13 patients with MPD who all had associated breast ductal carcinoma, both Paget cells and underlying ductal carcinoma exhibited the phenotype (MUC1+MUC2-MUC5AC-). This mucin phenotype is also expressed by Toker cells, which have been identified in the epidermis of five of 50 nipples in mastectomies without MPD. Of the three patients with perianal PD who all had associated rectal adenocarcinoma, Paget's cells expressed MUC2 constantly but expressed MUC1 and MUC5AC variably. Seven patients with intraepidermal vulvar PD and two patients with scrotal-penile PD had no identifiable underlying malignancy. Paget cells from all of these nine cases of EMPD expressed a uniform phenotype of mucin (MUC1+MUC2-MUC5AC+). One case of vulvar PD associated with underlying apocrine carcinoma had a phenotype (MUC1+MUC2-MUC5AC-) identical to that of normal apocrine glands. The skin appendage and Bartholin's glands from 20 normal-appearing vulvar skin samples and anal glands from 10 hemorrhoidectomies were also studied. Only Bartholin's gland expressed a mucin phenotype identical to that of intraepidermal EMPD. The results of the present study indicate that 1) MPD may arise from either mammary glands or epidermal Toker cells, 2) intraepidermal EMPD in the anogenital areas may arise from ectopic MUC5AC+ cells originating from Bartholin's or some other unidentified glands, and 3) unique expression of MUC2 in perianal PD indicates its origin from colorectal mucosa. We conclude that the study of mucin gene expression is useful in identifying the histogenesis of PD.

Depigmented genital extramammary Paget's disease: a possible histogenetic link to Toker's clear cells and clear cell papulosis

BACKGROUND

The histogenesis of extramammary Paget's disease (EMPD) is still controversial. Benign pagetoid cells of the nipple first described by Toker and the similar clear cells found in white maculopapules of clear cell papulosis (CCP) have been proposed to be potential precursor cells giving rise to EMPD and primary intraepidermal Paget's disease in the nipple. The observation of a rare case of depigmented EMPD provided us with a chance to examine further the interesting Toker's clear cell/CCP hypothesis.

METHODS

We performed pathologic studies, including Fontana-Masson stain and immunostaining for AE1/AE3 and S100P, on a new case of depigmented EMPD manifesting a 4 x 3 cm hypopigmented-depigmented patch on the root of the penis.

RESULTS

The lesion showed extensive intraepithelial proliferation of atypical pagetoid cells with markedly reduced epidermal melaninization but nearly normal numbers of melanocytes. The tumor cells were strongly positive for AE1/AE3 by immunostaining. Some tumor cells displayed tadpole-like morphology resembling the pagetoid cells of CCP. Such morphology was not observed in two random examples of non-depigmented genital EMPD.

CONCLUSIONS

The findings of tadpole-shaped pagetoid cells and depigmentation in the present case suggest that depigmented EMPD may be histogenetically related to CCP. Depigmented EMPD should be considered in the differential diagnosis of vitiligo, depigmented mycosis fungoides and lichen sclerosus located along the milk line.

Benign proliferative nipple duct lesions frequently contain CAM 5.2 and anti-cytokeratin 7 immunoreactive cells in the overlying epidermis

Benign proliferative nipple duct lesions (PNDLs) pose a diagnostic problem for clinicians and pathologists. Clinically, they may be associated with skin changes typically present in Paget's disease of the nipple. The identification of numerous scattered cells in the epidermis that are immunoreactive for low-molecular-weight cytokeratin may lead to further confusion with Paget's disease. We studied the nipple epidermis in nine cases of PNDL and compared them with 26 histologically normal nipples from mastectomy specimens. CAM 5.2 and anticytokeratin 7 (CK7) immunoreactive cells were identified in the epidermis of seven of nine nipples associated with PNDL. The cytokeratin-positive cells appeared cytologically benign and were dispersed singly (scattered in seven of seven cases and frequent in four of seven cases) or formed small aggregates with occasional tubular structures (three of seven cases) in the basal and middle layers of the epidermis. In two of seven cases, these epidermal immunoreactive cells showed continuity with the underlying PNDL, suggesting the spread or continuation of lesional cells to the epidermis. Dispersed single immunoreactive cells were identified in small numbers (scattered) in the basal layer of the epidermis in 12 of 26 normal nipples and more frequently in 1 of 12 cases. In all cases, the intraepidermal cells were negative for carcinoembryonic antigen (CEA) and Her-2/neu. We conclude that intraepidermal CAM 5.2 and anti-CK7 immunoreactive cells, which are normally present in the nipple epidermis, may proliferate and form aggregates when there is an underlying PNDL. The presence of these cells does not imply Paget's disease when the intraepidermal cells have a bland cytologic appearance, fail to overexpress Her-2/neu, and there is no carcinoma within the PNDL or elsewhere in the breast.

Genital Paget's disease with clear cells in the epidermis of the axilla

We report an 84-year-old man with extramammary Paget's disease (EMPD) involving the genital region. Microscopic examination revealed very few clear cells appearing pagetoid in the lower portion of prickle cell layer of the right axilla epidermis, with no clinically detectable eruption. Their histochemical, immunohistochemical and lectin-binding reactions were almost identical to those in the genital lesion. However, although the axillary lesion was diagnosed as subclinical Paget's condition, the clinical course showed no aggressive or destructive nature. Our case suggests that not all subclinical Paget's conditions become malignant, and that in some cases the clear cells may be precursors of Paget's cells developing multifocally.

Clear cell papulosis of the skin

Clear cell papulosis is a new entity first described in 1987. To date, six patients have been reported: all were young Taiwanese children. The disease is characterized clinically by multiple small, whitish maculopapules distributed along the milk line and by the presence of large, benign pagetoid cells in the epidermis resembling the clear cell of the nipple. The significance of this entity lies in its potential histogenetic link with Paget's disease of the skin. We report four new Taiwanese patients, three girls and one boy, aged between 21 months and 4 years. Two were sisters. Small hypopigmented macules first appeared on the pubis. They were eventually distributed bilaterally along the milk line but were most numerous in the public area. The disease may easily be overlooked when the macules are tiny or few in number and thus display no clear milk-line distribution, or when they occur in white-skinned individuals. Histologically, solitary large clear cells with large, round pale nuclei were detected in the basal layer of the hypomelaninized epidermis. The numbers of clear cells varied on haematoxylin and eosin staining and were only small in two patients. The cytoplasm of the clear cells was decorated by antikeratin AE1 and anticarcinoembryonic antigen antibodies. AE1 was the best marker of the clear cell. Some of the AE1-positive cells were tadpole-like in shape and were situated well above the basal layer. Ultrastructurally, large clumps of disintegrated or vacuolated mucin granules were present in the cytoplasm of the clear cells. The melanocytes appeared normal; the suprabasal keratinocytes were essentially devoid of melanosomes. The pathological findings in the present study support the hypothesis that these clear cells are an aberrant derivative of sweat gland cells in the epidermis and are potentially the precursor cells giving rise to mammary and extramammary Paget's disease. The differential diagnosis includes chicken pox scars, idiopathic guttate hypomelanosis, hypomelanotic tinea versicolor, anetoderma and early, hypopigmented lesions of Paget's disease.

Clear cell papulosis: case report and literature review

Clear cell papulosis is a newly described skin disease characterized by multiple white papules. Histopathologically, diagnostic clear cells were seen among the basal cells of the epidermis. We report clear cell papulosis on the lumbar area and buttocks of a 1-year-old girl.