Case 68

Presentation

A 47-year-old man with a history of a melanoma excised from his distal right calf 18 months earlier returns for routine follow-up. The pathology for that lesion was a 1.33-mm thick, Clark’s level IV, nonulcerated melanoma that was vertical growth phase positive. He underwent a wide local excision with sentinel lymph node mapping and biopsy that showed no residual melanoma and no tumor in two sentinel lymph nodes. He now presents with a 6-week history of a 2-cm area of reddish-tinted nodules proximal to his melanoma scar that was nontender. He does not feel that the nodules have changed in the 6 weeks since he noticed them.

▪ Clinical Photograph

Figure 68.1

Physical Examination Report

The raised erythematous lesions are visible proximal to the scar (arrow).

Differential Diagnosis

There are a variety of nonneoplastic and benign cutaneous conditions that can explain a subcutaneous nodule, including dermatofibroma, angiolipoma,
and folliculitis. However, any nodule presenting within the lymphatic drainage field of a previously resected melanoma should be considered a potential in-transit metastasis. In-transit metastases develop within the lymphatic vessels of the skin and can be either intradermal or subcutaneous. Although typically pigmented (pink or red in color), in-transit nodules may be nonpigmented. Also, although intransit disease typically occurs between the site of the primary melanoma and the draining nodal basin, lesions can appear distal to the primary scar, often in the lower extremities.

▪ Approach

Nodules that are suspected to be in-transit melanoma can be confirmed pathologically by either excisional biopsy or fine-needle aspiration. For the initial lesion, in which the level of suspicion and the certainty of the diagnosis is less secure, a simple excision of the nodule under local anesthesia is appropriate. For recurrent disease, the diagnosis is more obvious because multiple similarappearing nodules may be present. Fine-needle aspiration can establish the diagnosis of in-transit melanoma if the nodule has enough bulk to allow insertion of the needle into the mass. Although the margin of excision is well defined for primary melanomas, there are no clear guidelines for the margin of excision of in-transit nodules. A simple excision with 3 to 5 mm of normal tissue around the melanoma is adequate because local recurrence of the resected in-transit nodule is not an important clinical issue. The entire region of the body is at significant risk for new lesions. Wide excisions, particularly with skin grafts or attempts to obtain margins of 2 to 4 cm, should not be performed. Patients suffer significant morbidity for no benefit, because the disease can recur anywhere within the skin drained by that lymphatic basin. Similarly, there is no role for adjuvant radiation therapy because radiation cannot be given circumferentially to an extremity, and there is no defined margin for the radiation field.

Another point of surgical management of an initial isolated in-transit melanoma nodule is whether a sentinel lymph node mapping and biopsy should be done at the area of the in-transit nodule. This technique will map a lymph node or nodes at that site, and there is a possibility of defining microscopic spread to the draining nodal basin. However, it is not standard of care to perform sentinel node mapping with resection of in-transit melanoma. Arguments against adding a node biopsy are that patients already have stage III by having an in-transit lesion, and patients in this situation are more likely to recur with other in-transit nodules or systemically. It is appropriate after identifying in-transit disease to stage a patient with computed tomography (CT) scans of the chest, abdomen, and pelvis, or with a positron-emission tomography (PET) scan.

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