Primary Cutaneous Adenoid Cystic Carcinoma of the Back: A Case Report

Abstract

Adenoid cystic carcinoma (ACC) is a rare type of carcinoma that arises from the salivary glands. When ACC is present on the skin with no other primary site of malignancy in the body, it is termed primary cutaneous adenoid cystic carcinoma (PCACC). The only way to differentiate between ACC and other benign cutaneous masses is through the use of histopathology and immunohistochemistry. This case report describes a 67-year-old Asian female with a history of an epidermal inclusion cyst. She was seen in consultation with general surgery for the removal of a mass on her lower back. The initial excision's pathology revealed an ACC with perineural invasion. However, there were positive margins, as the mass was originally thought to be benign. Consequently, she underwent a second procedure for the total excision of the mass, resulting in subsequent negative margins. The patient was referred to radiation oncology; however, she ultimately opted to defer postoperative adjuvant radiation therapy, with the understanding that she would undergo biannual screening examinations.

Keywords: adenoid cystic carcinoma; epidermal inclusion cyst; perineural invasion; radiation therapy; skin cancer.

Figure 1. A 3-cm non-erythematous firm mobile nodule.

The first surgical excision revealed positive margins. Upon wide local re-excision, the lesion measured nine centimeters from medial to lateral, and four centimeters from superior to inferior, with a depth of one and a half centimeters. The skin surface appeared pink-brown and smooth. The specimen was serially sectioned from lateral to medial. This image is representative, as one was not taken before surgery [10].

Figure 2. Histopathology of specimen.

Histopathologic images were taken from the excised specimen. (A) H&E at 10x magnification; (B) H&E at 40x magnification. Both magnifications showed evidence of dermal epithelial proliferation without connection to the epidermis, as well as nests of basaloid cells with tubular and cribriform morphology. Occasional mitotic figures are present. (C) Immunohistochemistry (IHC) demonstrated diffuse, strong positive reactivity for CD117 in the tumor cells. (D) The images also show evidence of perineural invasion.