Malignant Hidroacanthoma Simplex: A Case Report

Abstract

Hidroacanthoma simplex is a benign tumor of the skin originating from or showing differentiation to the sweat glands. It grossly resembles seborrheic keratosis of Bowen's disease and histologically shows intraepidermal focal growth of epithelial cells. Malignant transformation of this tumor is rare. We report a case of pigmented hidroacanthoma with malignant transformation in a 67-year-old woman. There was a 20-year history of a skin lesion on the right thigh, which first appeared as a small verrucous papule, progressed to a dark-brown colored patch, and then to a pigmented plaque. Histologically, the primary tumor was composed of small squamoid cells with marked cellular atypia. Most of the tumor cells were located in the epidermis. Immunohistochemically, the cytoplasm of some tumor cells showed a positive reaction for epithelial membrane antigen, but not for either carcino-embryonic antigen or the S-100 protein.

Porocarcinoma Arising in Pigmented Hidroacanthoma Simplex

“…The gross appearance of malignant HAS tended to vary, and there were nodular lesions or keratotic plaques with or without erosion and/or ulceration. [4][5][6][7][8][9][10][11] In the present case, the porocarcinoma portion was erosive with depigmentation, and such a case has been reported previously. 3 Therefore, clinical findings such as erosion and/or ulceration and depigmentation might be indicative of the malignant transformation of HAS.…”

“…12 Malignant variants of HAS are rare and have been reported under different names, such as malignant HAS, in situ porocarcinoma, eccrine porocarcinoma, and HAS with invasive growth. [2][3][4][5][6][7][8][9][10][11] Most cases developed from pre-existing benign HAS, 3,5,7,11 as did our present case. In a review of the literature on malignant HAS, 6 the ages of patients ranged from 50 to 87 years, with the majority of patients being over 70 years of age.…”

“…2 Malignant HAS is extremely rare, and most of the reported cases have coexisted with HAS and, thus, represent the malignant transformation of pre-existing HAS. [3][4][5][6][7][8][9][10][11] In general, poroid neoplasms are believed to be of eccrine gland origin but poroid neoplasms are currently categorized as being of either eccrine or apocrine origin and, in particular, poroma with follicular and/or sebaceous differentiation is referred to as apocrine poroma. 12 Among a variety of cutaneous tumors, pigmentation and secondary amyloid deposition are found most frequently in basal cell carcinoma and seborrheic keratosis.…”

A case of porocarcinoma arising in pigmented hidroacanthoma simplex with multiple lymph node, liver and bone metastases

“…Poroma and HAS usually lack melanocytes and melanin pigments. However, there have been a few reports of pigmented HAS, and most of these cases had a malignant component 5–9 . Dendritic melanocytes have also been seen in some cases of porocarcinoma.…”

“…Porocarcinoma may arise de novo or be associated with pre‐existing poroma and hidroacanthoma simplex (HAS) 3 . HAS is an intraepidermal variant of poroma, 4 and pigmented HAS is an extremely rare variant with dendritic melanocytes within the tumor nests and/or melanin pigment in the tumor cells 5–9 …”