Co-expression of Myoepithelial and Melanocytic Features in Carcinoma Ex Pleomorphic Adenoma

Abstract

The presence of melanin pigment and melanocytic markers expression have been rarely reported in salivary gland tumors. Herein, two cases of carcinoma arising in pleomorphic adenoma of the parotid gland and showing diffuse expression of myoepithelial and melanocytic markers are described. The clinical-pathological clues useful in the differential diagnosis with melanoma are discussed. In addition, a review of the pertinent literature is also proposed, discussing the pathologic mechanisms potentially involved in this phenomenon.

Cutaneous Melanomas: A Single Center Experience on the Usage of Immunohistochemistry Applied for the Diagnosis

“…Nevertheless, HMB-45 is negative in most of the tumors that could histologically mimic cM and be positive for S-100 and SOX-10, so we often add it to the immunohistochemical panels adopted in these diagnostic settings [ 32 , 43 ]. HMB-45 could turn out positive in PEComa and related tumors, melanotic schwannoma, clear cell sarcoma, sex cord-stromal tumors, MiT family translocation renal cell carcinomas, pheochromocytoma, and rare cases of salivary gland tumors (as previously specified, it reacts with the fibrillar matrix in stage II melanocytes and should be more appropriately considered an organelle-specific marker, rather than a lineage-specific marker) [ 44 , 45 , 46 , 47 ]. In the melanocytic lesions, HMB-45 strongly reacts with the junctional and intraepidermal melanocytes; in our experience, it is the best marker for the evaluation of the junctional component, with an intensity that correlates with the grade of the dysplasia in dysplastic cN [ 48 , 49 ].…”

“…MART-1 strongly reacts with the junctional, intraepidermal, and dermal melanocytes in both cN and cM; we always performed it in conjunction with HMB-45, in order to evaluate the silhouette of the melanocytic lesion (symmetry/asymmetry), estimate the depth of invasion in cM, and assess the lympho-vascular invasion, adnexal involvement, and peri-adnexal extension [ 48 , 51 , 52 , 58 ]. However, dermatopathologists should be aware that: (1) cN with neurotization and/or stromal metaplasia, congenital cN, and hyper-maturating cN could completely lose or show a gradual diminishing of the expression of MART-1; (2) MART-1 could be expressed by adrenal cortical tumors, PEComa and related tumors, mesotheliomas, salivary gland tumors, and sex cord-stromal tumors (interestingly, some authors showed that these tumors do not produce MART-1 RNA, thus concluding that this “apparently paradoxical” positivity is related to an immunologically cross-reaction with unrelated antigens) [ 47 , 52 , 58 , 60 , 61 , 62 ]. Because of its high sensitivity for melanocytic lesions, MART-1 is a useful marker for the pathological evaluation of SLNB, in order to identify, but not to differentiate, NN and MM (both MART-1(+)) [ 62 , 63 ].…”

Primary non-cutaneous melanomas of the head and neck: Case series and review of the literature

“… 9 However, it has been reported a few cases of other salivary gland tumors, including carcinomas, staining positively for melanocytic markers. 10 …”