Clear (pale) cell acanthosis as an incidental finding

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.

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.

Seborrheic Keratosis With Prominent Clear Cell Changes-A Rare But Important Diagnostic Variant

Seborrheic keratoses, although exceedingly common, occasionally have morphologic similarities to other lesions that complicate a typically straightforward diagnosis. The authors present a case of a 69-year-old man with a left shoulder lesion that displayed characteristic clinical and microscopic features of seborrheic keratosis on biopsy. However, diffuse and prominent clear cells were also noted. These stained strongly with Periodic acid-Schiff and were diastase sensitive, suggestive of glycogen accumulation and possible trichilemmal differentiation. This case is presented to demonstrate a unique and striking example of clear cell change within a seborrheic keratosis and to briefly review the published literature on this finding, which is rarely reported and demands close examination to exclude more aggressive neoplasms.

Clear cell proliferations of the skin

Clear cell proliferations of the skin consist of a diverse group of lesions characterized by the presence of cells with abundant clear cytoplasm. They may arise from primary, metastatic, or non-neoplastic origins, with their distinctive cytoplasmic clearing attributable to causes ranging from artifact to accumulation of materials such as glycogen, mucin, or lipids. Despite the heterogeneity of these lesions, their distinguishing characteristics may be subtle, especially at high power. As such, histologic diagnosis can be challenging, and proper consideration relies on an understanding of the scope of possible origins, etiologies, and key immunohistochemical staining patterns of the various entities. This review categorizes cutaneous clear cell neoplasms by histogenesis, and offers differential diagnostic strategies to aid in their clinicopathologic evaluation.

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 of the areola and nipple: clinical, histopathological, and immunohistochemical features of two Brazilian cases

Clear cell acanthoma or Degos' acanthoma is a distinct disease concerning its clinical, histopathological, and immunohistochemical features. Its pathologic nature - whether neoplastic or reactive - is still under dispute among researchers. The disease shows a chronic course and often presents with a single papulonodular lesion on the lower limbs of adults. However, cases with multiple lesions, sometimes occurring in an eruptive fashion, and with clear variation in the size and shape of the cutaneous lesions have been reported. So far, five cases in which the lesions were exclusively located in the nipple area have been reported, all in Korean women. Four of these cases mimicked eczema and one, a polypoid nodule. The aim of this article is to present clinical, histopathological, and immunohistochemical features of two additional cases in Brazilian women with similar nipple topography.

Myrmecia wart inclusions as an incidental histopathologic finding

BACKGROUND

Latent infection by human papillomavirus (HPV) has been described for genital (mucosal) and epidermodysplasia verruciformis subtypes. Only rarely has cutaneotropic, non-oncogenic HPV been found by polymerase chain reaction studies in normal skin.

METHODS

We noted myrmecia wart inclusions as an incidental histopathologic finding in four specimens from diverse sites (eyebrow, scalp, forehead, leg). The final diagnoses for these four cases were intradermal nevus, scarring alopecia, benign keratosis and stasis dermatitis. Anti-HPV antibody staining was performed in all cases. This antibody detects HPV-1,6,11,16,18 and 31 in formalin-fixed paraffin-embedded tissue.

RESULTS

The foci of myrmecia wart inclusions were characterized by smooth to angular cytoplasmic inclusions in the granular layer, spanning one to three rete. The inclusions stained with an anti-HPV antibody in three specimens.

CONCLUSIONS

This finding of incidental myrmecia wart inclusions in skin biopsies supports latent infection by cutaneotropic, non-carcinogenic HPV.

Solitary epidermolytic acanthoma: a clinical and histopathological study

BACKGROUND

Epidermolytic acanthoma (EA) is an uncommon cutaneous entity that typically presents as a solitary lesion, or, less commonly, as multiple or disseminated discrete lesions. It usually appears at or after middle-age, and has been reported in various locations including the face, trunk, extremities and genitalia. Histopathologically, EA shows epidermolytic hyperkeratosis (EHK) involving either the entire thickness of the epidermis or just the granular and upper spinous layers.

OBJECTIVE AND METHODS

To describe the clinical and microscopic features of EA, we retrospectively reviewed all cases diagnosed as EA at the Skin Pathology Laboratory at Boston University between 1999 and 2009.

RESULTS

Solitary EA is more common in men (65%) and usually presents as a hyperkeratotic papule on the trunk (45%) or extremities (25%). Histopathologically, all cases of solitary EA showed the classical features of hyperkeratosis, acanthosis and EHK. Three architectural patterns were observed on scanning magnification: papillomatous (55%), cup-shaped (40%) and acanthotic (15%). Additional common features encountered included focal parakeratosis (85%), and a sparse to mild superficial perivascular lymphocytic infiltrate (90%).

CONCLUSION

This large case series of solitary EA reviews the clinical features of this entity and describes several new histological variants.