Apocrine Hidradenocarcinoma of the Scalp: A Classification Conundrum

Marc Cohen 0 1 2 David S. Cassarino 0 1 2 Hubert B. Shih 0 1 2 Elliot Abemayor 0 1 2 Maie St. John 0 1 2 0 H. B. Shih UCLA School of Medicine , Los Angeles, CA, USA 1 D. S. Cassarino Department of Pathology and Laboratory Medicine, UCLA School of Medicine , Los Angeles, CA, USA 2 M. Cohen (&) E. Abemayor M. St. John Division of Head and Neck Surgery, UCLA School of Medicine , 10838 Le Conte Ave, Rm 62-132 CHS, Los Angeles, CA 90095, USA Introduction The classification of malignant sweat gland lesions is complex. Traditionally, cutaneous sweat gland tumors have been classified by either eccrine or apocrine features. Methods A case report of a 33-yearold Hispanic man with a left scalp mass diagnosed as a malignancy of adnexal origin preoperatively is discussed. After presentation at our multidisciplinary tumor board, excision with ipsilateral neck dissection was undertaken. Results Final pathology revealed an apocrine hidradenocarcinoma. The classification and behavior of this entity are discussed in this report. Conclusion Apocrine hidradenocarcinoma can be viewed as an aggressive malignant lesion of cutaneous sweat glands on a spectrum that involves both eccrine and apoeccrine lesions. - The skin is the largest organ of the body and is composed of two principal layers, the epidermis and dermis. Arising out of the ectoderm and eventually existing within the dermis are specialized structures referred to as skin appendages. Skin appendages are subdivided into three categories: the pilosebaceous unit, the eccrine cutaneous sweat gland, and the apocrine cutaneous sweat gland. Eccrine sweat glands are found throughout the body but especially on the palms and soles. Apocrine sweat glands tend to be limited to the face, axilla, and anogenital areas [1]. Skin adnexal tumors can arise from any of these skin appendages. For example, pilosebaceous units are thought to give rise to trichilemmal carcinoma and sebaceous carcinoma. Some examples of tumors of supposed eccrine origin include porocarcinoma and hidradenocarcinoma, though apocrine differentiation of the former has been seen as well. Apocrine carcinoma and syringocystadenocarcinoma are thought to have apocrine origins. Hence, there usually exists a pilosebaceous, eccrine, or apocrine predominant morphology which allows classification of skin adnexal tumors into one of these three groups of origin [1, 2]. As previously mentioned, hidradenocarcinoma is traditionally regarded as a malignancy of eccrine cutaneous sweat glands. In this report, we present a case of a patient with a hidradenocarcinoma with apocrine features. The dilemma of classifying this lesion and its behavior will be discussed. A 33-year-old man presented with a 4 month history of an enlarging left scalp mass. The patient denied any pain or parasthesias associated with the mass or any history of trauma to the area. He did note that the mass would occasionally bleed. He had no history of significant sun exposure, alcohol or tobacco use. Physical examination revealed a 5 9 5 9 4 cm painless mass at the left posterior scalp (Fig. 1). The mass appeared to be extremely vascular with normal overlying skin. The mass did not feel to be fixated to the underlying calvarium. In addition, multiple enlarged left level V lymph nodes were palpated. The mass was evaluated by both computed tomography (CT) and magnetic resonance (MR). On CT, the mass was clearly identified and noted not to have an calvarial involvement. By MR imaging, the mass was relatively isointense on T1 weighted images, slightly bright on T2 weighted images with flow voids (Fig. 2). On both MR and CT, the presence of significant left-sided cervical adenopathy was evident. A PET scan was also obtained which showed abnormal uptake at the left posterior scalp and mid-left lower neck. No distant lesions were identified. Incisional biopsies were performed and a diagnosis of a malignant adnexal neoplasm was given. The patient was presented at our multidisciplinary tumor board and the recommendation was to perform a wide local excision of the primary mass and a modified radical neck dissection of the ipsilateral neck. The decision to give postoperative adjuvant treatment would be made after final pathology. The patient underwent wide local excision of the mass and a left neck dissection of levels IV. Surgical margins were achieved. On microscopic exam, the mass was consistent with an infiltrative carcinoma with clear cell morphology and focal squamous differentiation, with focal sebaceous differentiation and connection to a hair follicle, numerous duct-like structures, and myxoid stroma (Figs. 3 and 4). Immunohistochemical staining was grossly positive for HMW-cytokeratin (Fig. 5) and focally positive for CEA. CAM 5.2, CK7, CK20, S-100, TTF-1, and CDX2 Fig. 1 After the patients scalp has been shaved, the 5 9 5 9 4 cm mass at the left parietal scalp as seen upon initial presentation were all negative. A final diagnosis of apocrine hidradenocarcinoma was made. Although adnexal malignancies comprise \1% of all head and neck cancers, it is nevertheless important for the head and neck surgeon to understand the classification and behavior of these tumors. As mentioned, adnexal tumors have been classified based on their predominant morphology. Traditionally, these tumors were categorized as having a pilosebaceous, eccrine, or apocrine origin. However, some investigators have pointed to the existence of tumors of mixed morphology, such as tumors exhibiting both apocrine and eccrine differentiation. This has prompted the suggestion that certain skin adnexal tumors may arise out of a totipotent stem cell instead [1]. More relevantly, such observations have prompted some to question the usefulness and accuracy of traditional designations of cutaneous sweat gland tumors as either of eccrine or apocrine in origin [24]. The traditional association of hidradenocarcinoma with eccrine morphology compared to our current observation of apocrine hidradenocarcinoma certainly supports this line of thought. Several other examples help explain the motivation behind questioning traditional eccrine and apocrine designations. First is the aforementioned example of the existence of mixed eccrine/apocrine lesions such as syringocystadenoma papilliferum and poroma [2]. Second, many tumors which have been previously classified as apocrine have been found in areas where apocrine glands typically do not exist [3]. Third, closer examination of many lesions traditionally classified as eccrine have revealed the existence of apocrine and apoeccrine counterparts as well [2]. Given that many past examples of eccrine or apocrine designation of cutaneous sweat gland tumors were based on poor or incomplete evidence, Ko and colleagues undertook a study carefully examining the histological and immunohistochemical characteristics of a series of six hidradenocarcinomas. Their conclusion was that all the samples demonstrated histological features (...truncated)