Poroma - Causes, symptoms, diagnosis and management

Introduction:

Poroma is a cutaneous benign adnexal tumor. This tumor develops at the terminal ductal portion of the sweat gland and is also called a parotid tumor. Earlier it was believed that a poroma is an eccrine tumor. Later, there have been multiple presentations of poroid tumors that develop from apocrine, sebaceous, and/or follicular sweat glands. Poromas of eccrine and apocrine origin develop from the terminal portion of these sweat glands. This terminal duct is known as acrosyringium, hence the name acrospiroma.

Some researchers named poroma nodular hidradenoma, clear cell hidradenoma, hidroacanthoma simplex, dermal duct tumors, and/or hidradenoma. Poromas are generally solitary, well-circumscribed, and small cutaneous tumors. This occurs at any age ranging from 6 months to 95 years. There is no gender discrimination in the prevalence of poroma. Poroma does not have any racial or ethnic predilection. Poroma can transform into a malignant tumor when left untreated for a long duration. This malignant counterpart of poroma is called porocarcinoma.

What Is the Cause of Poroma?

Researchers have not yet concluded the exact cause of poroma. Studies are still being conducted to know the exact reason for the benign transformation of the sweat gland. Known causes that have been identified are:

• Long-term radiation exposure.

• Immunosuppression.

• Exposure to certain chemical agents.

• Chronic exposure to light.

Poroma is also found to be associated with various types of conditions like Bowen’s disease and hypohidrotic ectodermal dysplasia. The malignant variant of poroma is commonly found to be associated with conditions such as Xeroderma pigmentosum, extramammary Paget disease, Hodgkin’s lymphoma, Sarcoidosis, human immunodeficiency virus (HIV), pernicious anemia, and Hodgkin's lymphoma. Poroma is also commonly found among pregnant mothers and patients receiving chemotherapy, radiotherapy, or electron therapy.

What Is the Pathophysiology of Poroma?

Poroma is a benign adnexal tumor. It develops on the skin and does not affect any internal tissues. The cancer shows the differentiation of cells into glandular ductal cells. These are called poroid cells. Porocarcinoma which is a malignant counterpart shows clear poroid differentiation.

What Are the Signs and Symptoms of Poroma?

Poromas are very rare tumors of the skin. They usually are solitary and do not cause any pain or discomfort. These are stable, slow-growing tumors that occasionally cause slight pain. Poromas are dome-shaped papules or nodules. The color of poroma may vary from skin color, pink, red, brown to purple color. The surface of the poroma may be smooth or ulcerative. Due to the high vascularity of poroma, it mimics pyogenic granuloma, and the lesion bleeds readily with minor trauma.

In some people, poroma may be itchy and mildly tender. When the poroma develops sudden itching with pain, bleeds easily, and the surface becomes ulcerative, it may be an indication of malignant transformation, i.,e porocarcinoma. It may appear on any part of the body, head and neck, areola, nipple, armpits, upper and lower limbs, scrotum, and buttocks. But the most common locations of poroma are palms and soles. Patients undergoing chemotherapy or radiotherapy develop multiple poromas, and this condition is called porokeratosis.

What Are the Subtypes of Poroma?

There are four subtypes of poroma:

1. Hidroacanthoma Simplex Poroma - Poroma is confined to the upper layer of the skin, i.e., the epidermis of the skin.

2. Dermal Duct Poroma - These poromas are confined to the dermis layer of the skin.

3. Hidradenoma - These poromas are further divided into clear cell hidradenoma and poroid hidradenoma. Clear cell hidradenoma arises from apocrine sweat glands, and poroid hidradenoma arises from eccrine sweat glands.

4. Eccrine Poroma - These poromas are tumors of eccrine sweat glands.

How Is a Poroma Diagnosed?

The extent of diversity and rarity makes it very challenging to diagnose a poroma. Clinical presentation and histopathology are the only reliable facts that confirm the diagnosis of poroma. Histopathology is the study of the tissue specimen that is obtained from the lesion. The biopsy is the procedure to be followed to obtain a tissue sample from the lesion site. The biopsy is performed under anesthesia.

Blood investigations do not play any role in diagnosing poroma. Diagnosis can be confirmed after excisional biopsy with subsequent histopathological examination. Incisional biopsy is generally not recommended since the lesion is very small, and further excisional biopsy can be considered as a treatment option. Imaging studies include magnetic resonance imaging (MRI), computed tomography (CT), and X-ray. Imaging studies are not necessary for such types of benign cutaneous lesions. There are no other tests recommended for the diagnosis of poroma.

Poroma Histology: Poroma appears to be a well-circumscribed tumor. Based on the location of the tumor cells, poroid tumors are classified into four subtypes. These are eccrine poroma, poroid hydradenoma, hidroacanthoma simplex, and dermal duct tumor. These tumors are completely intraepidermal and this type of growth is known as hidroacanthoma simplex. Dermal duct tumors are poroid tumors that are situated within or nearly intradermal. Eccrine poroma can be situated in continuity with the epidermis called juxta-epidermal poroma. Poroid hidradenomas are completely situated in the dermal layer.

Poroid cells are cuboidal keratinocytes showing a non-palisading pattern and monomorphic ovoid nuclei with discrete nucleoli. Malignant tumor features can be observed in poromas. These include the number of mitoses, highly vascularized stroma, and foci of necrosis. A specific type of poroid tumor is linked with the presence of dendritic melanocytes with scattered poroid cells within intraepidermal tumor nests. The histological features correlate clinically with the pigmented variant of poroma known as pigmented hidroacanthoma simplex.

Research has proposed four histopathological features to differentiate apocrine from eccrine poroma. These include:

• Elongated tubules are lined by columnar cuticular or polygonal cells, displaying hints of apocrine secretion across the luminal border. These contain an amorphous, eosinophilic material within the lumina.

• Aggregates of neoplastic cells, that connect to preexisting infundibula can be seen. This resembles connections between the excretory ducts of apocrine glands.

• Follicular differentiation is manifested as epithelial lobules. This means tumors of the follicular infundibulum or trichoblastoma.

• The isolated sebocytes and small neoplastic cells in clusters are seen.

Porocarcinoma consists of anaplastic cells, that are characterized by large irregular and hyperchromatic nuclei, with glycogen-rich cytoplasm. Porocarcinoma exhibits necrosis, and the presence of mitotic figures. This proliferates intraepidermal before it extends to the dermis. It invades dermal lymphatics and the tumor shows regional and distant spread.

What Are the Treatment Modalities for Poroma?

For superficial lesions, electrosurgical destruction or shaving can be performed to remove the benign tumor. For deeper cutaneous lesions, excisional biopsy or simple surgical excision can be performed. Excisional biopsy is the procedure where the entire tumor or the area under suspicion of tumor is removed. Poromas do not require any medical care, except for post-operative care that is to be followed. The doctor may prescribe medicines that help avoid any secondary infections and medicines that provide relief from pain and discomfort. The treatment of poroma is optional, up to the patient since it has mild to no discomfort or pain. It rarely undergoes a malignant transformation.

What Are the Complications of Poroma?

There are no complications post-surgically for poroma. Secondary infection and hemorrhage may be caused, which is associated with any other minor surgical procedure.

What Is the Prognosis for Poroma?

After surgery, poromas rarely reappear. Poromas are solitary, self-limiting benign lesions that do not grow more than 2 cm in diameter. Poromas have less clinical significance; hence prognosis is good. Few patients develop multiple poromas at a time. This condition is called porokeratosis. The malignant transformation of a pre-existing poroma into a porocarcinoma is very rare.

Conclusion:

Poromas are asymptomatic solitary benign cutaneous lesions. They rarely undergo malignant transformation. Long-standing poromas may transform into porocarcinoma. The duration of malignant transformation is not yet confirmed by the researchers. Poromas are not life-threatening tumors. Depending on the location of the poroma, they may cause esthetic discomfort to the patient.