[Malignant degeneration of linear hidroacanthoma simplex].

We describe an 88-year-old woman with various lesions in the right submammary region that had remained stable for more than 40 years. She reported rapid growth and ulceration of one of the lesions in the past year. The examination showed a firm tumor of diameter 7 cm below the right breast. The surface of the tumor was keratotic at the periphery and ulcerated in the middle with foul-smelling serous exudate. Adjacent to the lesion, there were various smaller erythematous brownish tumors with a velvety surface, and with a linear distribution (Figure 1). No enlarged local or regional lymph nodes were palpated. Laboratory workup, chest x-ray, electrocardiogram, bilateral mammography, and right axillary ultrasound were all normal. An incisional biopsy of the larger tumor and another biopsy of one of the adjacent lesions were taken. In the first case, the hematoxylin-eosin stain showed irregular, anastomosed islets composed of intraepidermal tumor cells, some of them pigmented, with a clearer cytoplasm than the surrounding keratinocytes. Abundant atypical cells with large, irregular, hyperchromatic nuclei were observed inside the tumor masses. In some sections, cystic spaces within these nests of basaloid cells could be seen. The epidermis presented hyperkeratosis, foci of parakeratosis, and irregular acanthosis (Figure 2 A and B). A biopsy of the smaller lesion showed well-defined nests of uniform cuboidal cells with rounded, basophilic nuclei showing no atypia, and with cystic structures in the interior (Figure Malignant Degeneration of Linear Hidroacanthoma Simplex