Cutaneous Clear Cell Neoplasms

Abstract

Cutaneous clear cell neoplasms represent a heterogenous group of several primary and metastatic tumors with diverse histogenesis. Tumors with widespread clear cell change can seem strikingly similar under the microscope resulting in diagnostic difficulties. Although most cases are idiopathic, intracytoplasmic accumulation, artifact of tissue processing, and degenerative phenomenon have been cited as possible causes of clear cell change. An awareness of the various entities demonstrating this attribute, judicious use of ancillary techniques, and knowledge of the clinical setting are crucial to the accurate diagnosis. This review details the histological features of clear cell neoplasms of the skin with particular emphasis on the discriminating features.

Clear Cell Proliferations of the Skin: A Histopathologic Review

“…41 Controversy still exists on the existence of TC, first introduced by Headington in 1976, as a separate entity. 39–41 According to some authors, this tumor does not correspond to an authentic carcinoma with tricholemmal differentiation but rather to a clear cell variant of SCCs. 41 Clinically, it arises in actinically damaged skin of older individuals, typically involving the scalp, face, or ears and usually presents as a rapidly growing, exophytic, sometimes ulcerated, nodule.…”

“…It clinically presents as an isolated, slow growing, verrucous papule, appearing most commonly on the face or neck of adults. [39][40][41] The presence of multiple lesions is a major criterion for the diagnosis of Cowden syndrome, which results from a germline mutation of the tumor suppressor PTEN gene and is associated with multiple extracutaneous neoplasms (breast, thyroid, and gastrointestinal tract). 42 Histopathologically, tricholemmoma exhibits a lobular epidermal downgrowth into the dermis (Fig.…”

“…Hemorrhage and necrosis are seen in larger tumors. 39,40,[46][47][48][49] It is important to distinguish TC from clear cell SCC because of the more favorable prognosis of the former. Features that may help in this distinction include the characteristic lobular growth pattern, peripheral palisading, and adnexal extension in TC, as well as positive staining with antibodies directed against hair follicle specific keratins such as AE13 and AE14.…”

“…TC generally has a nonaggressive course with only rare local recurrences and can be treated successfully with a wide excision. [39][40][41] Clear Cell Trichoblastoma Trichoblastoma (TB) is a benign neoplasm with differentiation toward follicular germinative cells and the stroma of the follicular papillae. Clinically, it presents as a solitary skin-colored papule, typically on the scalp or central face.…”

“…TC generally has a nonaggressive course with only rare local recurrences and can be treated successfully with a wide excision. 39–41…”