Dermoscopic Appearance of Intraluminal Hematogenous and Lymphatic Patterns of Cutaneous Melanoma Metastases

Cutaneous melanoma metastases can be categorized into satellite (≤2 cm from primary melanoma), in-transit (>2 cm from primary melanoma but not beyond the regional nodal basin), and distant metastases (>2 cm from primary melanoma and beyond the regional nodal basin). The presence of cutaneous melanoma metastases is a component of the American Joint Committee on Cancer 2010 TNM (tumor node metastasis) staging system and is a poor prognostic criterion.¹ Dermoscopy is a skin imaging technique using a handheld device that permits visualization of colors, structures, and patterns in skin lesions not evident to the naked eye. We describe 2 patients with in-transit cutaneous melanoma metastases having unusual clinical and dermoscopic features and distinct microanatomic routes of melanoma dissemination.

Patient 1 was diagnosed as having a primary cutaneous melanoma of the left forehead (stage IIIC; Breslow thickness, 2.1 mm), which was treated with wide local excision. A year later, the patient received localized irradiation for satellite skin metastases. One year after that, skin examination revealed 6 blue macules on the mid frontal scalp more than 2 cm from the excision scar. Dermoscopy revealed nonblanching bluish lines in a branched pattern (Figure 1A). No palpable lymphadenopathy was detected and positron emission tomography–computed tomography (PET-CT) revealed no evidence of distant metastases. Histopathologic examination of a skin biopsy specimen confirmed in-transit metastatic melanoma with atypical melanocytes present in superficial dermal lymphatics (Figure 1B).

Patient 2 had a history of multiple primary melanomas and presented for dermatology follow-up. The most recent melanoma, on the right chest (stage IIIA; Breslow thickness, 0.75 mm) had been diagnosed 5 years earlier and was treated with wide local excision. The axillary sentinel lymph node biopsy findings were positive, and the patient elected to undergo completion lymphadenectomy. Skin examination revealed 8 blue-gray macules on the right chest, all more than 2 cm from his excision scar. Dermoscopy revealed nonblanching, red-bluish, fuzzy, branching lines (Figure 2A). No palpable lymphadenopathy was detected, and PET-CT revealed no evidence of distant metastases. Histopathologic examination of a skin biopsy specimen confirmed in-transit metastatic melanoma with atypical melanocytes present in superficial dermal blood vessels (Figure 2B).

Studies have identified the most common dermoscopic features of cutaneous melanoma metastases, including peripheral gray spots, “atypical” vessels, and a blue nevuslike pattern.^2,3 To our knowledge, there are no reports of a blue or red-blue, linear, branched dermoscopic pattern associated with cutaneous melanoma metastases, although we acknowledge that authors may have previously categorized this pattern as atypical vessels.

The histopathologic findings in our cases suggest that the dermoscopic color differences correspond to unique microanatomic routes of melanoma dissemination, with blue and red-blue lines corresponding to lymphatic and hematogenous tumoral dissemination, respectively. A blue dermoscopic color has been correlated with the presence of melanin in the dermis.⁴ Intraluminal melanoma dissemination within lymphatic dermal vessels would therefore be expected to produce branched blue lines. A red color may be observed if significant red blood cells were admixed with intraluminal melanoma cells, such as within dermal blood vessels.

Noting the correlation between dermoscopic and histopathologic features, previous studies have investigated the potential utility of dermoscopy, an in vivo, noninvasive skin imaging technique, at identifying prognostic or biologic characteristics of melanoma such as tumor thickness⁵ or horizontal growth rate.⁶ While the factors driving lymphatic vs hematogenous in-transit dissemination of melanoma remain unknown, as do any differences in their biologic significance, our finding is an intriguing clinical-dermoscopic-histopathologic observation.

Corresponding Author: Michael A. Marchetti, MD, Dermatology Service, Department of Medicine, Memorial Sloan Kettering Cancer Center, 160 E 53rd St, New York, NY 10022 (marchetm@mskcc.org).

Published Online: September 24, 2014. doi:10.1001/jamadermatol.2014.2006.

Conflict of Interest Disclosures: None reported.