A case of hidroacanthoma simplex.

We report a case of hidroacanthoma simplex with giant lesion that was found on the left lumbar part which was treated with surgical excision.

What was known?

Hidroacanthoma simplex is a rare benign eccrine adnexal tumor.

Introduction

Hidroacanthoma simplex is a rare benign eccrine adnexal tumor. Here, we present a case of hidroacanthoma simplex with giant lesion that occurred on the left lumbar region.

Case Report

A 62-year-old Chinese woman presented with a 50-year history of brown tumor on the left lumbar part. She described a pink-colored indolent nodule that had appeared on her left lumbar region 50 years ago. The nodule was circumscribed and protruding over the peripheral skin. She did not feel any pruritus or pain at the tumor site. The tumor enlarged quickly in the last 2 years. And the color of tumor surface became dark gradually. No previous history of trauma on the area could be elicited. Her medical and family history was noncontributory.

Physical examination revealed a 7.0 × 4.8 × 0.5 cm, well-circumscribed, brown-colored, sessile tumor on the left lumbar part. The surface was covered with rough reddish-brown crusts [Figure 1]. The tumor was firm, nontender, and nonbleeding. There was no sentinel lymphandenopathy. Thorax CT scan and abdomen ultrasonic examination both were normal. Under local anesthesia, a biopsy was performed on the edge of the tumor.

Figure 1

A 7.0 × 4.8 × 0.5 cm, well-circumscribed, brown-colored, sessile tumor on the left lumbar part. The surface was rough with reddish-brown crusts

The histopathology showed broad anastomosing tracts of cuboidal cells, with uniform nuclei originating from the epidermis in the tumor tissue. It was constructed by basal-like cells with uniform size and shape. Tubular structures were appeared within the neoplasm. There was no atypia or mitosis of cells [Figures 2-4]. Immunohistochemical study showed the tumor tissue sections were positive for EMA [Figure 5] and negative for CK7, 17, 18. So the patient was confirmed as a case of hidroacanthoma simplex by histopathology and immunohistochemical study.

Figure 2

The histopathology showed broad anastomosing tracts of cuboidal cells, with uniform nuclei originated from the epidermis in the tumor tissue. It was constructed by basal-like cells with uniform size and shape. Tubular structures were present within the neoplasm. There was no atypia, mitosis

Figure 4

Tubular structures appeared within the neoplasm

Figure 5

Immunohistochemical study showed the tumor tissue sections were positive for EMA

The histopathology showed broad anastomosing tracts of cuboidal cells, with uniform nuclei originating from the epidermis in the tumor tissue. It was constructed by basaloid cells with uniform size and shape. Tubular structures were present within the neoplasm. There was no atypia or mitosis.

The tumor was removed by surgery. The excision was extended 0.5 cm beyond the edge of the lesion, up to the adipose layer in depth. The histopathology of excisional mass border confirmed the tumor was removed entirely. Hybridization in situ indicated a negative reaction for human papilloma virus. The operation was successful. She had no recurrence after 6 months.

Discussion

In 1956, Smith and Coburn identified a new neoplasm, which had previously been considered as intraepidermal epithelioma of Borst Jadassohn, and they devised the term simple hidroacanthoma.[1] Thirteen years later, Holubar and Wolff found that the tumor cells had the same enzymatic activities as those of eccrine sweat gland ducts. These findings led them to suggest that simple hidroacanthoma might be a variant of eccrine poroma and they proposed to use the term “intraepidermal eccrine poroma”,[2] which has become widely accepted.

Hidroacanthoma simplex occurs most frequently on the lower extremities and the trunk. It is more common in older adults and without gender predilection. The gross appearance of hidroacanthoma simplex is characterized by flat or slightly elevated, irregularly verrucous, brown plaques. Sometimes the plaques are easily confused with those of seborrheic keratosis or basal cell carcinoma.[3-5]

Histologically, hidroacanthoma simplex exhibits the “Jadassohn phenomenon” and is composed of bland basaloid cells that are smaller than neighboring epidermal keratinocytes and resemble the so-called poroid cells of poroma. Intracytoplasmic glycogen and occasional ductal structures within the nests of cells are also characteristic of hidroacanthoma simplex.[3-5]

As to our case, the lesion appeared on her left lumbar part when she was 12-years old. And, the histopathology showed tubular structures within the neoplasm. So, it was diagnosed as hidroacanthoma simplex. To our knowledge, the biggest tumor varied in size 8 × 9 cm,[6] but there are no reports with detailed delineation in the English literature. In this case, the tumor was about 7.0 × 4.8 cm in size, which was also quite large.

Malignant variants of simple hidroacanthoma are rarely reported. An observation of atypical cells and mitotic cells in tumor nests, suggesting malignant transformation, was reported in 7 (10%) of 70 cases.[6] So hidroacanthoma simplex must be paid careful attention because of its noncharacteristic clinical appearance and its potential for malignant transformation. A complete surgical excision is the first choice of the treatment.

What is new?

A case of hidroacanthoma simplex with giant lesion occurring in the left lumbar region is reported here on account of its rarity.