Most patients present with sebaceous adenomas, but cystic sebaceous neoplasms have been reported as specific markers of MTS.
Sebaceous neoplasms, particularly carcinomas, are exceedingly rare.
Despite the pitfalls, some center may still opt to perform IHC on sebaceous neoplasms [ 89].
69 Sebaceous neoplasms in people with Lynch syndrome are more likely than sporadic neoplasms to occur prior to age 60 years (median age 56 years), be multiple rather than isolated, and occur in the context of a personal or family history of Lynch syndrome-related cancer(s).
More recent studies have shown IHC to be less reliable when performed on sebaceous neoplasms that are on colon or endometrial carcinomas [ 89, 90].
70 The incidence of sebaceous neoplasms among individuals with Lynch syndrome has been reported to be as high as 9% (Table 2).
In a similar vein to colorectal and endometrial carcinomas, IHC markers have been proposed as part of the work-up to identify patients presenting with sebaceous neoplasms requiring confirmatory DNA MMR gene mutational analysis [ 83, 87– 87].
65, 68 The presence of sebaceous neoplasms in individuals and families with other internal malignancies was referred to as Muir Torre syndrome before molecular genetic testing demonstrated a common underlying etiology.
Based on clinical observations, the association of colorectal cancers with brain tumors was named Turcot syndrome, and colorectal cancers associated with sebaceous neoplasms and keratoacanthomas were termed Muir Torre syndrome.
70 A recent publication describes a scoring system based on the number of sebaceous neoplasms, age at diagnosis, and personal and family history of Lynch syndrome-associated cancers, and concludes that IHC alone is a poor predictor for identifying people with Lynch syndrome.
