Superficial tumors refer to those originating from the skin, skin appendages, and subcutaneous tissue. Clinically, it is important to differentiate these tumors from non-neoplastic tumor-like masses.
Skin Papilloma
Skin papilloma is caused by epithelial hyperplasia forming papillary structures, which may extend into the subepidermal papillary dermis. It carries a risk of malignant transformation into skin cancer. For instance, penile papillomas are highly prone to becoming papillary squamous cell carcinoma.
Verruca (Wart)
This is not a true tumor and is commonly caused by viral infection. Its surface presents outwardly projecting papillae with multiple slender, columnar protrusions. The base is flat and does not extend beneath the epidermis. Spontaneous shedding may occur.
Senile Pigmented Wart
Commonly seen on the scalp, face, exposed areas, or trunk, this lesion protrudes above the skin surface, appears black, and presents as a plaque. Its surface can be dry, smooth, or rough. The base remains flat without subepidermal extension. If it enlarges, thickens, bleeds, or ulcerates, malignant transformation is possible.
Skin Cancer
Skin cancer most frequently appears as basal cell carcinoma or squamous cell carcinoma, often affecting the head, face, and lower limbs.
Basal Cell Carcinoma
Originating from the basal cells of the skin or its appendages, this tumor grows slowly and exhibits infiltrative growth, with rare hematogenous or lymphatic metastasis. Increased pigmentation can occur, presenting as pigmented basal cell carcinoma, which may be clinically mistaken for malignant melanoma but tends to be firmer. When ulceration occurs, the edges often appear rodent-like. This carcinoma frequently develops on the head and face, such as beside the nasal bridge or eyelids. It is radiosensitive and can be treated with radiotherapy; early surgical excision is also effective.
Squamous Cell Carcinoma
This carcinoma often presents with ulceration from an early stage. It frequently arises from chronic ulcers, chronic fistulas, or non-healing ulcers in scars that undergo malignant transformation. Its surface typically appears cauliflower-like, with raised and irregular edges and an uneven base. It bleeds easily and often becomes infected, resulting in a foul odor. Local infiltration and lymph node metastasis are common. Surgical treatment is primary, and regional lymph nodes should be dissected. The tumor is also radiosensitive, though achieving a cure by radiotherapy alone is challenging. In cases involving the lower limbs, severe disease with bone marrow infiltration may necessitate amputation.
Nevus and Melanoma
Pigmented Nevus
A pigmented nevus presents as a pigmented skin lesion and can be classified as:
- Intradermal nevus: Nevus cells reside in the dermis beneath the epidermis, often forming a raised lesion. The surface appears smooth and may contain hair (referred to as hairy nevus). Malignant transformation is rare.
- Junctional nevus: Nevus cells are located at the basal cell layer, extending beneath the epidermis. The lesion appears flat and deeply pigmented. These nevus cells are easily stimulated and may undergo malignant transformation following trauma or infection. This type is often found on the hands, feet, or other trauma-prone areas; rare forms can occur on the eyelids (referred to as closed nevus).
- Compound nevus: This involves both intradermal and junctional components. When a nevus darkens, enlarges, or becomes itchy or painful, the risk of malignancy increases. In such cases, complete excision with pathological examination is warranted. The presence of ulceration or bleeding should heighten clinical suspicion. Incomplete excision or chemical cauterization should be avoided. Although cryotherapy or electrocautery can remove the lesion, they do not provide pathological diagnosis, making it difficult to determine malignancy; thus, these methods are not recommended for general use.
Melanoma
Melanoma is a highly malignant tumor with rapid progression. The ABCD criteria assist in the early detection of melanoma:
- A – Asymmetry;
- B – Border irregularity;
- C – Color variation;
- D – Diameter greater than 6 mm.
For small lesions, complete excisional biopsy is preferred. For large lesions, partial biopsy may be performed initially, but once the diagnosis is confirmed, wide excision should follow promptly. Early radical surgical resection offers the best chance for cure. Retrospective studies have shown that amputation reduces quality of life without decreasing metastasis rates, so amputation is no longer advocated. Recent research has revealed that the development and progression of melanoma are closely related to mutations in key tumor targets and the immune microenvironment. Targeted therapy and immunotherapy have now become important treatment modalities in addition to surgery, radiotherapy, and chemotherapy.
Lipoma
Lipoma is a benign tumor composed of normal adipose tissue, most commonly found in the limbs and trunk. It presents as a well-defined, lobulated, soft mass that may appear encapsulated and is typically painless. Growth is slow, though lipomas may become very large. Deep-seated lipomas carry a risk of malignancy and should be excised in a timely manner. Multiple lipomas tend to be small, often symmetric, and may have a family history. Some cases are painful (referred to as painful lipomas).
Fibromas and Fibroma-like Lesions
These tumors arise in the skin and subcutaneous fibrous tissue. They are generally small, firm, and slow-growing. Several common types are described below.
Fibroxanthoma
This tumor is located in the dermis and subcutaneous tissue, commonly on the trunk and proximal upper arms. It often develops following minor trauma or itching that leads to the formation of small papules. Due to internal hemorrhage and the presence of hemosiderin, the lesion often contains brown pigment and appears coffee-colored. The lesion is firm, with poorly defined borders and an infiltrative feel, which can be mistaken for malignancy. The diameter typically remains under 1 cm; enlargement may suggest transformation into fibrosarcoma.
Dermatofibrosarcoma Protuberans
This tumor commonly arises on the trunk, originating in the dermis. The overlying skin appears thin and smooth, resembling a raised, keloid-like scar. It is a low-grade malignancy with a pseudocapsule. Local recurrence is frequent after excision, and repeated recurrences may increase malignancy and result in hematogenous metastasis. Surgical excision should include an adequate margin of normal skin and the corresponding deep fascia.
Desmoid Fibromatosis
This lesion typically occurs in the abdominal wall, often following abdominal muscle trauma or postpartum repair processes. It may contain proliferating striated muscle fibers. Although not a true tumor, it lacks a clear capsule and should be excised completely.
Neurofibroma
Neurofibromas arise from nerve fibers, which include the nerve axon and surrounding Schwann cells and fibroblasts. The term encompasses both schwannomas and neurofibromas. Schwannomas consist of Schwann cells, while neurofibromas contain specialized soft fibrous tissue and refractile neurofibrocytes with some nerve fascicles.
Schwannoma
When located superficially, schwannomas are often found along peripheral nerve trunks of the limbs.
Central type: Originating from the center of a nerve trunk, the tumor capsule is formed by the nerve fibers. The tumor is fusiform. Surgical dissection must follow the nerve’s longitudinal axis to avoid nerve transection; the tumor should be carefully separated within the capsule.
Marginal type: Originating at the nerve periphery, the nerve fascicles course along the tumor margin. Surgical removal is easier, with less risk of damaging the main nerve trunk.
Neurofibroma
Neurofibromas may contain adipose tissue and capillaries. They are usually multiple and often symmetric. Most cases are asymptomatic but may cause pain. Café-au-lait spots are often present on the skin, and the tumors can become pendulous, resembling breasts. Associated findings may include intellectual impairment, headaches, or dizziness of unknown cause, with a tendency for familial aggregation. Another form resembles an elephant-like tumor, often on the scalp or buttocks, with a lion-like appearance in some cases. The tumor consists of dense fibrous tissue with vascular sinuses. Bleeding can be difficult to control intraoperatively due to open vascular sinuses in the surgical field; therefore, incisions should be made through normal tissue. Large defects often require skin grafting.
Hemangioma
Hemangiomas can be classified structurally into three types, each with distinct clinical courses and prognoses.
Capillary Hemangioma
This is most common in infants, predominantly in females. Small red spots or patches on the skin are visible at birth or shortly thereafter, gradually enlarging and becoming raised. A hemangioma that grows faster than the infant's overall development is a true tumor. The lesion is well-defined, blanches slightly under pressure, and returns to red when released. Most cases are hamartomas, which cease growing or regress within one year.
Early-stage lesions respond well to treatment such as surgical excision or cryotherapy with liquid nitrogen. Larger lesions may also be treated this way, although scarring may occur. Additional treatments include 32P patches or X-ray irradiation to induce capillary thrombosis and tumor regression. In rare, extensive cases, oral prednisone may be attempted.
Cavernous Hemangioma
Typically composed of small veins and adipose tissue, these hemangiomas primarily occur in subcutaneous tissue but can also affect muscle, bone, or internal organs. Subcutaneous cavernous hemangiomas cause slight local protrusion. The overlying skin may appear normal, exhibit capillary dilation, or show a bluish discoloration. The tumor is soft with ill-defined borders, sometimes compressible, possibly with calcified nodules or tenderness. Intramuscular cavernous hemangiomas often lead to muscle hypertrophy and localized sagging; those in the lower limbs may cause a sensation of fullness with prolonged standing or walking.
Early surgical excision is preferred to prevent functional impairment and increased treatment difficulty due to tumor enlargement. Preoperative evaluation should accurately define the tumor extent, possibly with angiography. Intraoperatively, careful control of bleeding and thorough removal of the hemangioma tissue are required. As adjunctive therapy, local injection of sclerosing agents (such as 5% sodium morrhuate or 40% urea) may be used.
Racemose Hemangioma
This type consists of larger, tortuous vessels, primarily veins, though arteries or arteriovenous fistulas may also be involved. In addition to affecting subcutaneous tissue and muscle, racemose hemangiomas frequently invade bone and can span an entire limb. The tumor typically presents as tortuous blood vessels with significant compressibility and expansibility. Vascular murmurs or palpable hard nodules may be present. In the lower limbs, nutritional impairment of the skin can lead to thinning, pigmentation, or ulceration with bleeding. Involvement of multiple muscle groups can impair mobility. In young patients with bone involvement, the limb may appear lengthened and thickened.
Surgical resection is the treatment of choice. Preoperative angiography should be performed to delineate the extent of the tumor and assist surgical planning. Adequate preparation is needed to manage potential massive blood loss and facilitate intraoperative hemostasis and transfusion.
Cystic Tumors and Cysts
Dermoid Cyst
This cystic teratoma is commonly located superficially at the lateral brow or along cranial sutures, where it may extend intracranially in a doughnut pattern. Thorough preoperative assessment and planning are necessary.
Sebaceous Cyst
Not a true tumor, this retention cyst results from obstruction of sebaceous gland ducts. It is most common in areas with dense sebaceous glands, such as the scalp, face, and back. A small black spot representing the duct opening is often visible on the surface. The cyst contains a greasy, sebaceous mixture of keratinous material that can become secondarily infected, causing foul odor. Once infection is controlled, surgical excision is performed.
Epidermoid Cyst
This cyst develops following trauma that drives the basal layer of the epidermis into the subcutaneous tissue, where it continues to grow. The cyst wall is composed of epidermis, and the cavity contains keratinous scales. It is frequently found in areas prone to trauma or friction, such as the buttocks or elbows, and occasionally at injection sites. Surgical excision is the treatment.
Synovial Cyst
Not a true tumor, this cyst arises from superficial synovial bursae due to chronic strain. It commonly occurs near the wrist, dorsum of the foot, tendons, or joints, presenting as a firm mass. Treatment options include compressive rupture, aspiration with corticosteroid injection (e.g., hydrocortisone acetate), or surgical excision. However, recurrence is common.