Ectopic hamartomatous thymoma: a case demonstrating skin adnexal differentiation with positivity for epithelial membrane antigen, androgen receptors, and BRST-2 by immunohistochemistry

Ectopic hamartomatous thymoma — A truly rare neoplasm: Report of a case

“…Table 1 shows a summary of the cases of ectopic hamartomatous thymoma that have been reported since 1990. [2][3][4][5][6][8][9][10][11][12][13][14][15][16][17][18][19][20] These tumors are common during the third and fourth decades, with a marked male predominance. They most often arise in the lower neck region, in particular the supraclavicular or suprasternal region, and are located either superfi cially or deep in the sternocleidomastoid muscle.…”

“…Recognition of the characteristic histological and immunohistochemical features together with the site of the tumor should thus lead to a diagnosis of ectopic hamartomatous thymoma. 6,14,16,18 Although there is little information available on the male preponderance of this tumor, Weinreb et al 6 proposed that this tumor might grow in response to androgenic stimuli, based on the immunohistochemical androgen receptor expression in the spindle cell component of this tumor.…”

“…2,4 Nevertheless, the common consensus is that this tumor is of brachial origin because of its specifi c localization to the lower neck region. 2,6,8 On the other hand, some ectopic hamartomatous thymomas present salivary gland differentiation. 12 In addition, ectopic hamartomatous thymoma may be associated with heterotopic salivary gland, which can arise in the same anatomic location as ectopic hamartomatous thymoma and has a strong male predominance.…”

“…The development of epithelial tissues in the cervical sinus, if persistent, could explain the presence and growth of any structure potentially derived from primitive ectoderm. 6 Naturally, salivary gland differentiation could be derived from remnants of the cervical sinus. Fetsch et al 2 regarded this tumor as "branchial anlage mixed tumor," to more precisely refl ect the nature of this distinctive neoplasm.…”

“…1,2 The incidence of this tumor is very low, with only sporadic reports in the literature. [3][4][5][6] This tumor is pathologically characterized by a mixture of spindle cells, epithelial cells, mature adipose tissue, and lymphocytes. 1 The term "ectopic hamartomatous thymoma" was coined by Rosai et al in 1984, 7 based on the combined features of a hamartoma with those of a neoplasm, probably derived from abnormal thymic tissue.…”