Sclerosing Microcystic Adenocarcinoma of the Head and Neck Mucosa: A Neoplasm Closely Resembling Microcystic Adnexal Carcinoma

Abstract

Microcystic adnexal carcinoma (MAC) occurs predominantly in the centrofacial skin and has been only rarely reported in mucosal surfaces. We here present a 5 case series of tumors closely resembling MAC occurring in the mucosal surfaces of the head and neck, which we have termed sclerosing microcystic adenocarcinomas. These tumors showed a predilection for women (4:1) with an average patient age of 52.6 years (range 41-73 years). Location included the tongue (n = 2), the floor of the mouth (n = 2), and the nasopharynx/clivus (n = 1). One occurred after radiation therapy and another occurred in the setting of immune compromise. Immunohistochemistry highlighted a dual cell population with luminal cells showing positivity for high and low-molecular weight keratins and surrounding myoepithelial cells showing S100 and smooth muscle actin staining. No cases had nodal involvement, and the single patient with clinical follow-up was alive and free of disease 34 months after diagnosis and definitive radiochemotherapy. Differential diagnoses for all cases diverged from those provoked by MAC in the skin and included a variety of salivary gland neoplasms such as adenoid cystic carcinoma, polymorphous low grade adenocarcinoma, and mucoepidermoid carcinoma. Recognition of sclerosing microcystic adenocarcinoma in the head and neck mucosa is critical given its bland appearance and subtle infiltration pattern, infrequency of nodal involvement, and behavioral differences from the other entities on the differential.Keywords Sclerosing microcystic adnexal carcinoma Á Microcystic adnexal carcinoma Á MAC Á Head and neck Á Salivary gland carcinoma Á Mucosal

Microcystic adnexal carcinoma (MAC)-like squamous cell carcinoma as a differential diagnosis to Bell´s palsy: review of guidelines for refractory facial nerve palsy

“…However, rare examples have been described in the orbita, the external ear canal, the minor salivary glands, the vulva and the axilla [7]. To date, only six cases have been reported in non-cutaneous head and neck sites, including the tongue ( n  = 3), and one case each in the nasopharynx, floor of the mouth and parotid gland [9]. …”

Sequencing of Sclerosing Microcystic Adenocarcinoma Identifies Mutational Burden and Somatic Variants Associated With Tumorigenesis

“…To our knowledge, this is the first study to profile SMA at the molecular level (1,6). Previous studies have attempted molecular characterization of MAC; SMA has often been described as a variant of MAC owing to its histological resemblance to sweat glands and infiltrative pattern and tendency toward perineural invasion but with a more favorable prognosis (1)(2)(3)8). Mutations have been identified in CDKN4/6 and also in TP53 and JAK1 genes in approximately 20% of patients with MAC (9, 10).…”

“…Several previous studies have observed SMA in the context of treatment with immunosuppression. One case report involved a patient treated with glatiramer for multiple sclerosis, while another involved a patient undergoing stem cell transplantation for AML (1,6). The patient in this case report previously received treatment with methotrexate, infliximab, adalimumab and apremilast.…”

“…Sclerosing microcystic adenocarcinoma (SMA) is a rare neoplasm that histologically resembles microcystic adnexal carcinoma (MAC) but is found in extracutaneous areas of the head and neck without adnexal associations (1)(2)(3). Like MAC, SMA is characterized by thin nests and cords of squamous/basaloid cells including ducts and cystic spaces suggesting a possible origin from eccrine sweat glands or the pilosebaceous-apocrine unit (4,5).…”

“…SMA was first established as an entity distinct from MAC in a five-patient case series, including one case in the context of immunosuppression (acute myeloid leukemia or AML treatment) (1). A separate case of SMA was identified in the context of a patient diagnosed with multiple sclerosis previously treated with the immunosuppressive agent, glatiramer (6).…”