Porocarcinoma C44.L

Rare, malignant, infiltrating sweat gland tumor originating from the intraepidermal part of the eccrine sweat gland excretory duct. Retrograde ingrowth into the epidermis is characteristic.

Incidence: 0.01-0.005%. m:w=1:1 (Salih AM et al. 2017)

The average age in a meta-analytical search was 67.6 years. The average duration of the disease was 5.57 years and ranged from <1 year to 60 years.

The head and neck are most frequently affected (39.9%), followed by the lower extremities (33.9%). The genital area is less frequently affected.

Moderately fast-growing, squamous or nodular epithelial tumor with or without ulceration. The tumours are highly variable in terms of appearance, size and location. Porocarcinomas often develop on the basis of a poroma that has existed for years. The clinical malignancy criterion is a sudden rapid growth of a pre-existing tumor (see figure). Porocarcinomas can also develop complicatively in a nevus sebaceus. Eczmatoid changes are described less frequently.

In 31% of cases, metastases are already present at the time of initial clinical presentation. The most common organ to which porocarcinoma metastasizes is the regional lymph node (57.7 %). Seeding of epidermotropic metastases is possible. Visceral metastases rarely develop (Salih AM et al. 2017).

Often arising at the base of a poroma, asymmetric carcinoma that broadly infiltrates the deeper portions of the dermis (and subcutis). Tumor formations with reticularly branched, ribbon-like structures that make broad-based contact with the surface epithelium are characteristic. As in poroma, the formation of ductal as well as light cell structures is possible. Cell formations of small basaloid cells with chromatin-rich nuclei are seen. Abundant mitoses. Evidence of mass necrosis (see also under poroma).

The intraepithelial form of porocarcinoma is called malignant hidroacanthoma simplex. It is characterized by poroid epithelial clusters with densely packed tumor cells, numerous mitoses, and a markedly increased proliferation rate.

Moderately rapid growth. In the presence of lymph node metastases, the mortality rate is over 65%.

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