Squamoid Eccrine Ductal Carcinoma

Abstract

Squamoid eccrine ductal carcinoma (SEDC) is a rare and underrecognized primary cutaneous tumor with a high risk for local recurrence and metastasis. The tumor has a biphasic histologic appearance consisting of a superficial portion indistinguishable from squamous cell carcinoma (SCC) and a deeper component demonstrating eccrine ductal differentiation. Because of superficial sampling, SEDC often is misdiagnosed as SCC during the initial biopsy. The diagnosis usually is made during complete excision when deeper tissue is sampled. Confirmation of the diagnosis can be achieved by immunohistochemical positivity for carcinoembryonic antigen (CEA), epithelial membrane antigen (EMA), cytokeratin (CK) 5/6, and p63. In this article, we review the clinical and histologic details of 5 patients with SEDC who underwent successful treatment with Mohs micrographic surgery (MMS) at a single institution between November 2018 and May 2020. We also review the histologic patterns that helped distinguish SEDC from SCC upon complete excision. Our findings support the use of MMS as the treatment of choice for SEDC, given that all of the patients we reviewed required more than 1 Mohs stage for complete tumor clearance, and none demonstrated evidence of recurrence or metastasis after a mean follow-up period of 11 months.Cutis. 2021;107:E5-E9. Squamoid eccrine ductal carcinoma (SEDC) is an aggressive underrecognized cutaneous malignancy of unknown etiology. 1 It is most likely to occur in sun-exposed areas of the body, most commonly the head and neck. Risk factors include male sex, increased age, and chronic immunosuppression. [1][2][3][4] Current reports suggest that SEDC is likely a high-grade subtype of squamous cell carcinoma (SCC) with a high risk for local recurrence (25%) and metastasis (13%). 1,3,5,6 There are as few as 56 cases of SEDC reported in the literature; however, the number of cases may be closer to 100 due to SEDC being classified as either adenosquamous carcinoma of the skin or ductal eccrine carcinoma with squamous differentiation. 1 Clinically, SEDC mimics keratinocyte carcinomas. Histologically, SEDC is biphasic, with a superficial portion resembling well-differentiated SCC and a deeply invasive portion having infiltrative irregular cords with ductal differentiation. Perineural invasion (PNI) frequently is present. Multiple connections to the overlying epidermis also can be seen, serving as a subtle clue to the diagnosis on broad superficial specimens. [1][2][3] Due to superficial sampling, approximately 50% of reported cases are misdiagnosed as SCC during the initial biopsy. 4 The diagnosis of SEDC often is made during complete excision when deeper tissue is sampled. Establishing an accurate diagnosis is important given the more aggressive nature of SEDC compared with SCC and its proclivity for PNI. 1,3,6 The purpose of this review is to increase awareness of this underrecognized entity and describe the histologic findings that help distinguish SEDC from SCC.

Squamoid Eccrine Ductal Carcinoma of the Eyelid: Clinicopathologic Correlation of a Case

“…6,11 Immunosuppression has been suggested as a potential risk factor not only because of the association with older age but also due to the fact that several cases of SEDC have been reported in patients with a history of chronic lymphocytic leukemia or immunosuppression after organ transplant. 3,6 The patient in this study had no history of hematologic malignancy or immunosuppressive medication use. Though the typical presentation of these lesions include the presence of a nodule, papule, or plaque, 3,6,[9][10][11][12] there are cases where an ulcerated lesions were described.…”

“…3,6 The patient in this study had no history of hematologic malignancy or immunosuppressive medication use. Though the typical presentation of these lesions include the presence of a nodule, papule, or plaque, 3,6,[9][10][11][12] there are cases where an ulcerated lesions were described. 6,11 Histopathology of the case is consistent with that of prior cases of SEDC: the presence of focal squamous differentiation predominately in the epidermis and superficial dermis combined with the growth of ducts and strands in the deeper dermis.…”

“…11,12 Metastatic carcinoma can be ruled out with the use of immunohistochemistry, namely p63 and CK5/6, whose positivity confirms the primary cutaneous nature of the malignancy. 3,10,12 The distinction between SEDC and SCC deserves special attention as SEDC can easily be mistaken for SCC. These misdiagnoses have at least, in part, resulted from the use of superficial diagnostic biopsies such as shave or scoop biopsies.…”

“…3,6 The patient in this study had no history of hematologic malignancy or immunosuppressive medication use. Though the typical presentation of these lesions include the presence of a nodule, papule, or plaque, 3,6,9–12 there are cases where an ulcerated lesions were described. 6,11…”

“…2 Accurate diagnoses of these lesions can be difficult given both their rarity and histologic variability. 3 Furthermore, the histopathology of these entities can resemble metastatic carcinoma from sites such as the breast, lung, and kidney. 4…”