Pathological Conditions

Inflammatory disease biopsies require histology and close correlation with clinical details as do tumourous lesions which can arise from all the structures in the three skin layers resulting in a range of benign and malignant conditions.

Cysts: there is a variety of benign epithelial cysts that usually occur in the dermis and present as a dermal swelling. The type of cyst is determined by microscopic examination of the cell lining. Common examples are pilar and epidermal inclusion cysts - clinically termed sebaceous cysts.

Melanocytic naevi (moles): most Caucasians have several benign moles or naevi on their body, the number relating to sun exposure and to the age of the patient. Naevi vary both in size and colour. They may be the patient's skin tone, white or red through to shades of brown to blue/black in colour. Melanocytic naevi are removed for various reasons. They may have changed in appearance or develop symptoms suspicious clinically of malignant change requiring excision for histological examination. Naevi are also removed for cosmetic reasons, because they are being traumatised, occur at a hidden site on the body or constitute a newly formed naevus in an adult. There is a variety of histological types of benign naevi that are dependent on microscopic examination for correct diagnosis.

Malignant melanomas: malignant melanomas, like benign naevi, are derived from melanocytes. They may arise de novo or from within an existing melanocytic naevus. Changes in a pre-existing mole that cause concern include (a) asymmetry; (b) irregular borders; (c) change or variation in colour; (d) size > 6 mm; (e) elevation and also itching, bleeding or symptoms associated with a naevus. When the clinician is suspicious of a diagnosis of malignant melanoma the lesion is removed in total, usually with an ellipse of normal skin around it. Depending on the degree of certainty of the clinical diagnosis, a wide excision may or may not be done at that time. Melanomas are the third most common malignant skin tumour. Their incidence is rising and they are the primary skin tumour most likely to metastasise and cause death. Malignant melanomas typically occur after puberty and their incidence increases with advancing age.

Actinic keratosis, Bowen's disease, basal cell carcinoma, squamous cell carcinoma: most skin cancers and pre-cancerous lesions of the skin are related to chronic sun exposure in white skin and their incidence is increasing. Other aetiological factors include a genetic predisposition and immunosuppression. Patients who have had organ transplants are at greater risk of developing skin neoplasia.

Actinic (solar) keratosis: actinic keratoses present usually as multiple red scaly lesions on sites of chronic sun exposure, particularly the head and neck, back of hands and forearms. The lesions are usually removed and submitted for pathology when the clinician is concerned that there may be malignant change, and particularly invasive malignancy. Often, patients with actinic (solar) keratosis have multiple lesions which are treated by a variety of topical agents and are not submitted for histological examination. Various biopsy techniques may be used to remove actinic keratoses including curettage, shave, punch and excision biopsies.

Bowen's disease (carcinoma in situ): Bowen's disease is a pre-invasive or in situ malignancy of the skin usually presenting as a red scaly patch. Most of these lesions present in a background of solar damage although it can occur in areas of non-sun-damaged skin where it may be associated with a higher incidence of internal malignancy. Bowen's disease is often treated by dermatologists with topical agents and may be biopsied to confirm the diagnosis and to exclude invasive malignancy. Occasionally there will be a biopsy to remove the lesion. Depending on whether the biopsy is excisional or diagnostic in intent the laboratory will receive either a curettage, shave, punch or elliptical specimen.

Basal cell carcinoma: basal cell carcinoma is the commonest malignant tumour of the skin, and overall in humans. The vast majority is associated with chronic sun exposure and occur in the head and neck area of fair-skinned people. A few occur at sites of scarring in the skin and a small number of patients with a genetic predisposition develop multiple basal cell carcinomas. These patients often present at an early age. Basal cell carcinomas have a variety of clinical appearances from a nodular lesion to an ulcer or scarred areas and they may also be multifocal. The colour of the tumours can vary. The cell of origin of basal cell carcinoma is thought to be either the basal cell layer of the epidermis or hair follicle. Basal cell carcinomas are locally aggressive tumours, often infiltrating and destroying adjacent tissue. They do not, however, metastasise to other sites. The treatment of choice is surgical removal. The clinician may submit a variety of specimen types to the laboratory depending on the surgical technique used. These may be curettage, shave, punch or excision. Based on clinical need, Mohs' micrographic surgery is used in the treatment of a small number of cases. Occasionally, basal cell carcinomas may be treated by radiotherapy following a confirmatory diagnostic biopsy.

Squamous cell carcinoma: squamous cell carcinoma is the second most common malignant tumour of the skin typically at sun-exposed sites in patients with fair skin. A small number of squamous cell carcinomas occur in patients with predisposing genetic disorders, or at sites of chronic scarring. These tumours arise from the surface epithelium. They have a variety of clinical appearances including nodules and ulcers and they also can vary in colour. These tumours do have the potential to metastasise although the vast majority are cured by adequate local treatment. The treatment of choice is surgical and the clinician will submit various specimens including curettage, shave, punch and excision biopsies. Mohs' micrographic surgery may be used in selected cases. Some cases are treated with radiotherapy following a pathological diagnosis.

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