Nodular melanoma

Overview

Nodular melanoma (NM) is the most aggressive form of melanoma. It grows in vertical direction from the outset and grows very fast (months). Nodular melanoma has no known precursor. It is a small black, or if amelanotic, pink nodule that simply enlarges. The lesions tend to bleed. The microscopic hallmarks are:

• Dome-shaped at low power

• Epidermis thin or normal

• Dermal nodule of melanocytes with a “pushing” growth pattern

• No "radial growth phase"

Symptoms

Early signs of melanoma include the ABCDEs: asymmetry of lesion; border irregularity, bleeding, or crusting; color change or variegation (some lesions are amelanotic [nonpigmented]); diameter larger than 6 mm or growing lesion; evolving (surface changes (raised, bleeding, crusting) or symptomatic (itchiness or tenderness). About 1% to 2% of primary melanomas arise from mucous membrane melanocytes. Approximately 5% to 10% of patients present with metastatic disease (usually in the lymph node basin) without an identifiable primary lesion. Less than 2% of patients present with visceral metastases in the absence of an unknown primary lesion.

Diagnosis

As with nonmelanoma skin cancers, biopsy is indicated for all suspicious pigmented lesions. Surface epiluminescence microscopy (dermatoscopy) and ultrasound are evolving adjunctive noninvasive diagnostic techniques. 4 According to the American Academy of Dermatology (AAD) guidelines, whenever possible the lesion should be excised with narrow margins for diagnostic purposes. An incisional biopsy technique is appropriate when suspicion for melanoma is low, the lesion is large, or it is impractical to perform a complete excision. A repeat biopsy should be performed if the initial biopsy specimen is inadequate for accurate histologic diagnosis or staging. Fine needle aspiration cytology should not be used to assess the primary tumor. Histologic interpretation should be performed by a pathologist experienced in the microscopic diagnosis of pigmented lesions

Treatment

According to the AAD's 2001 guidelines, surgical management of primary cutaneous melanoma should focus on obtaining an excision margin based on histologic confirmation of tumor-free margins.

1. Melanoma in situ: 0.5 cm margins

2. Melanoma with Breslow's thickness <2 mm: 1.0 cm margins

3. Melanoma with Breslow's thickness ≥2.0 mm: 2.0 cm margins

In certain circumstances, surgical management needs to be tailored to the individual case. Primary melanomas near a vital structure might require a reduced margin, and aggressive histologic features can suggest a more worrisome tumor and warrant a wider margin. Surgical excision at sites such as the fingers, toes, soles, and ears also need separate surgical considerations. Mohs' micrographic surgery might prove useful for excision of melanoma, especially lesions located on the head, neck, hands, and feet. However, there are no formal recommendations pending additional studies. Studies suggest that the current recommendation of 0.5 mm margins for lentigo maligna (melanoma in situ) is often insufficient. Mohs' micrographic surgery and margin-controlled excision of lentigo maligna offer lower recurrence rates and allow tissue to be conserved. Despite adequate surgical resection of the primary melanoma, approximately 15% to 36% of patients with stages I and II melanoma will have some form of recurrence or metastasis during their clinical course. Routine laboratory tests and imaging studies are not required for asymptomatic patients with primary cutaneous melanoma 4 mm or less in thickness for initial staging or routine follow-up. Indications for such studies are directed by a thorough medical history and complete physical examination. However, some studies have suggested that a chest x-ray and serum lactate dehydrogenase (LDH) might help detect occult metastases and alter further clinical management.