Primary Noncutaneous Malignant Melanoma of the Breast

Abstract

Primary noncutaneous breast melanoma without an apparent skin primary lesion is uncommon. Its pathogenesis is debated with some authors believing that it is a metastatic disease from an undiscovered primary or a primary that has since completely regressed but it may be a true primary tumor arising from ectopic melanocytes. We present a case of a V600E BRAF mutation-positive primary noncutaneous breast melanoma diagnosed at an early stage in a screening mammogram as a solitary breast lesion without nodal involvement. Considerations of treatment of this rare disease are discussed.

Malignant melanoma of the breast: controversies in the diagnosis and therapeutic management of a rare nosologic entity

“…Molecular analysis for the BRAF V600E gene has been carried out in only four of the 15 patients with three cases reported positive and one negative. 3,4,10,13 Breast cancers can be classified into four major molecular subtypes based on the expression of specific genes including luminal A, luminal B, human epidermal growth factor receptor 2 (HER2)-enriched, and basal-like breast cancer. Triple-negative breast cancers (TNBCs), characterized by the absence of ER, PR, and HER2, account for~15% of all breast malignancies, while also being the most aggressive ones.…”

“…Most of the authors support that parenchymal PMMB can be a metastatic neoplasm of unknown origin, questioning the existence of primary malignancies of the breast. 4 Finding the primary melanotic lesions can be extremely difficult as a result of the regression of malignant melanomas and the inability to diagnose primary lesions of extracutaneous sites such as lymph nodes, subcutaneous tissues, or organs in the abdominal cavity. [16][17][18][19][20][21] Another theory suggests that noncutaneous PMMB constitutes a true primary tumor, developed from ectopic melanocytes in the breast parenchyma.…”

“…23 Furthermore, primary malignancies of breast parenchyma may be the result of a metaplastic transformation of a normal mammary duct. 4 Recent surveys, also, claim that the neoplastic cells of noncutaneous PMMB are not of embryological origin, but can be explained by the neoplastic genomic derepression. 22 Finally, Koh et al 3 assume that the presence of BRAF mutations in parenchymal PMMB cases indicate a similar pathogenic path with typical malignant melanoma.…”

“…Wide local excision with a 2 cm margin combined with sentinel lymph node biopsy composes the treatment of choice. 4,19 If axillary lymph nodes are clinically or pathologically involved, a lymph node dissection is required. Nevertheless, the updated guidelines propose either the intervention or a close follow-up with a possible adjuvant medical treatment.…”

“…Depending on the involvement of the skin, PMMB can be classified as cutaneous or noncutaneous. [2][3][4] Cutaneous primary malignant melanoma of the breast (PMMB) accounts for <5% of all melanomas and only 0.5% of all breast cancers. 2,3 The first case of noncutaneous PMMB, presenting as a breast lump, was described by Gatch in 1956, and since then only 14 noncutaneous cases have been reported in the literature, making it an exceedingly rare malignancy of the breast parenchyma.…”