Melanoma in situ with in-transit metastases

• Published in: JPRAS open Vol. 11; no. C; pp. 37 - 42
• Main Authors: Mikkelsen, Joachim, Hagen Wagenblast, Anne Lene, Behrendt, Nille, Lock-Andersen, Jørgen
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.03.2017; Elsevier
• Subjects: Follow-up; Guidelines; In-transit metastases; Melanoma; Melanoma in situ; Regression; In-transit metastases; Regression; Melanoma in situ; Melanoma; Follow-up; Guidelines
• ISSN: 2352-5878; 2352-5878
• DOI: 10.1016/j.jpra.2017.01.006

Melanoma in situ (MIS) is defined as the non-invasive precursor of malignant melanoma. It is widely considered to have no metastatic potential, and only few cases of metastasizing MIS have been reported. We describe a case of a 57-year-old Danish female who presented with in-transit metastases 14 months after excision of cutaneous MIS on the left femur. She had noticed two subcutaneous nodules develop over a short time proximal to the previous excision site. A needle biopsy and eventual complete excisional biopsy of both nodules confirmed the diagnosis of melanoma metastases. No further signs of metastases were found on additional imaging studies and the patient was assigned to the high-risk melanoma follow-up program. Of the few reported cases of metastasizing MIS, on review only three proved to be true MIS, defined by melanoma cells exclusively confined to the epidermis without dermal invasion through the basal membrane. Two of these had evident regression. Other studies of apparent metastatic MIS have revealed an invasive component on further sectioning of the specimens or by supplementary immunohistochemical staining. Although areas of regression could represent a former invasive melanoma giving rise to metastases, this remains speculative. Theoretically, our patient could also have had an occult primary melanoma metastasizing to the skin, but no sign of this was demonstrated on a PET/CT scan. Current treatment and follow-up guidelines for MIS do not recommend extensive surgery or frequent monitoring of patients, and upon diagnosis patients will routinely be told that there is no risk of metastases. This case shows what is generally considered impossible – metastasizing melanoma in situ. The finding had severe implications for the patient, and raises the question of whether to intensify follow-up or the extent of surgery in patients with melanoma in situ, especially when regression is present.