Primary Cutaneous Versus Salivary Gland Origin Mucoepidermoid Carcinoma

Abstract

Mucoepidermoid carcinoma (MEC) is a malignant glandular epithelial neoplasm that most commonly arises in the major salivary glands. Primary cutaneous MEC is very rare. There is a particular diagnostic challenge in determining the primary site of MEC when it is found in skin overlying the parotid gland. Attention to a combination of morphologic findings may be helpful. However, differentiation of primary cutaneous MEC from secondary cutaneous involvement by a parotid MEC may be unnecessary once the parotid gland is infiltrated. We report the case of a 54-year-old male with a 2-cm asymptomatic mass overlying the right parotid gland, which was managed by excision of the affected skin, right total parotidectomy, and right neck dissection. Histopathologic and immunohistochemical findings were consistent with a cutaneous intermediate-grade MEC. Postoperative radiotherapy was deferred. The patient showed no evidence of recurrence or metastasis at 2 months before self-discontinuing follow-up. To our knowledge, this is only the second reported case of MEC involving the parotid gland, but of overlying primary cutaneous origin.

Primary mucoepidermoid carcinoma of the external auditory canal with a CRTC1::MAML2 fusion: A case report and a review of literature

“…Mucoepidermoid carcinoma is a well-characterized malignancy of the major salivary glands with infrequent presentation in the sinonasal tract, lacrimal passages, bronchi, esophagus, thymus, breast, pancreas, prostate, and skin. 6 Although the etiopathology of cMEC is unclear, it has been postulated to arise from sweat glands or ectopic salivary glands. Its proposed origin from sweat glands is based on the shared ectodermal derivation of sweat glands and salivary glands and the identification of mucin in normal and tumoral sweat glands tissue.…”

“…By immunohistochemistry, the tumor cells express cytokeratin AE1/AE3, EMA, CEA, CK5/6, CK7, CK19, and p63. 1,2,4,[6][7][8][9][10][11]14,[16][17][18] Unlike the salivary gland, a grading system specific for cMEC has not yet been established and previous reports usually follow previous salivary gland grading systems that classify MECs into low-, intermediate-, and high-grade tumors based on various histopathologic features such as solid growth, perineural or lymphovascular invasion, necrosis, increased mitotic figures, and anaplasia. [19][20][21] Given the rarity of these tumors, they usually prompt several diagnostic considerations and subsequent workup.…”

“…Features that favor a cutaneous origin include an epidermal connection, presence of the tumor bulk in the dermis with only small tumor nests in the parotid gland, lymphocytic inflammation at the interface of the tumor and the parotid gland, and the presence of p63 reactivity. 6 Adenosquamous carcinoma is another diagnostic consideration, which is regarded as a high-grade and clinically aggressive neoplasm with high rate of local recurrence and metastasis. In contrast to adenosquamous carcinoma, cMEC does not have an overlying dysplastic squamous epithelium and lacks true squamous and well-differentiated adenocarcinoma features.…”

Primary cutaneous mucoepidermal carcinoma

“…Stewart first described MEC of parotid in 1945 3. There are case reports of origin from other organs like sinonasal tract, bronchus, oesophagus, thyroid, thymus, etc 1. Skin as the primary site of origin is a rare entity, the etiopathogenesis of which is not very clear.…”

“…MEC arises mostly from salivary gland with parotid gland being the usual site of involvement. Other sites which may develop primary MEC are lacrimal passages, sinonasal tract, oesophagus, bronchi, thymus, thyroid, breast, pancreas and prostate 1. Cutaneous involvement may be metastatic or primary.…”