Update on the pathology, genetics and somatic landscape of sebaceous tumours

Abstract

Cutaneous sebaceous neoplasms show a predilection for the head and neck area of adults and include tumours with benign behaviour, sebaceous adenoma and sebaceoma, and sebaceous carcinoma with potential for an aggressive disease course at the malignant end of the spectrum. The majority of tumours are solitary and sporadic, but a subset of tumours may be associated with Lynch syndrome, also known as hereditary non‐polyposis colon cancer (HNPCC) and previously referred to as Muir‐Torre syndrome (now known to be part of Lynch syndrome). This review provides an overview of the clinical and histological features of cutaneous sebaceous neoplasia with an emphasis on differentiating features and differential diagnosis. It also offers insights into the recently described molecular pathways involved in the development of sebaceous tumours and their association with Lynch syndrome.

An updated review of the sebaceous gland and its role in health and diseases Part 2: Pathophysiological clinical disorders of sebaceous glands

“…8,9 Sebaceoma can be differentiated from basal cell carcinomas by their negativity for CK20 and BerEP4 on immunohistochemistry. 9 Basaloid cells of a sebaceoma may also present with squamous metaplasia, sinusoidal, rippled, and carcinoid-like growth patterns, which may aid in the diagnosis of this tumor. 9 Sebaceomas do not exhibit necrosis or atypical mitoses, as these findings would be indicative of malignancy.…”

“…On the periphery, seboblasts predominate, the nuclei are round or oval, and the basaloid cytoplasm is less abundant. 9 Due to histological and clinical similarities, sebaceous hyperplasia is almost ways a differential diagnosis. However, in sebaceous adenoma, the peripheral basaloid layer will contain more than two layers of germinative cells, as opposed to sebaceous hyperplasia, which contains less than two ( Figure 4B).…”

“…However, in sebaceous adenoma, the peripheral basaloid layer will contain more than two layers of germinative cells, as opposed to sebaceous hyperplasia, which contains less than two ( Figure 4B). 9 Sebaceous adenoma has been adopted in the literature as an umbrella term, covering both superficial benign sebaceous neoplasms with a predominance of mature sebocytes and sebaceous neoplasms with a predominance of seboblasts. 4 In the former condition, papules or nodules-sometimes, though not always, yellowish in appearance-less than a centimeter in diameter present on the head, neck, and upper trunk.…”

“…9 Extraocular sebaceous carcinoma most often presents as erythematous nodules 18 or crusted plaques on the head, neck, or trunk, but has also been seen on the extremities or genitalia. 9 Nodular sebaceous carcinomas present cells in large lobules, whereas jagged nests are more characteristic of infiltrative sebaceous carcinomas ( Figure 6). 4 As with sebaceous adenoma, sebaceous carcinoma may be diagnosed by confirming sebaceous differentiation with epithelial membrane antigen and/or adipophilin immunoperoxidase staining.…”

“…Sebaceoma refers to a uni‐ or multilobular neoplasm typically presenting as skin‐colored or yellow nodules on the head or neck of an elderly female 9 . The tumor demonstrates immature germinative sebocytes with basaloid cytoplasm (>50% of cells) histologically, and expresses p63, p40, and CK7 positivity via immunohistochemistry 8,9 . Sebaceoma can be differentiated from basal cell carcinomas by their negativity for CK20 and BerEP4 on immunohistochemistry 9 .…”