Mixed Tumors With Follicular Differentiation: Complex Neoplasms of the Primary Epithelial Germ

Abstract

Apocrine mixed tumors of the skin illustrate the ability of pluripotential primordial cells to differentiate in different directions within an individual tumor. Moreover, mixed tumors appear as a compendium of different folliculo-sebaceous neoplasms. We suggest that these proliferations should be interpreted as "complex neoplasms of the primary epithelial germ."

Apocrine mixed tumor of the skin (“mixed tumor of the folliculosebaceous-apocrine complex”)

“…Additionally, they may manifest follicular and/or sebaceous differentiation, features supporting apocrine differentiation. [3][4][5][6] In contrast, eccrine mixed tumors show neither decapitation secretion nor follicular/sebaceous differentiation. Cutaneous mixed tumors are considered analogous to pleomorphic adenomas of salivary glands, but identical neoplasms are also recognized in lacrimal glands, ceruminal glands, and breast, with consistent homology at the microscopic, immunohistochemical, and ultrastructural levels.…”

Skin adnexal neoplasms—part 1: An approach to tumours of the pilosebaceous unit

“…The histogenesis of mixed adnexal tumours is still uncertain; however, the possibility of origin from a pluripotent stem cells is suggestive. 2 Most SAT are benign, and local complete surgical excision is curative. However, diagnosing some of these tumours has important implications, as they might be markers for syndromes associated with internal malignancies, such as trichilemmomas in Cowden disease and sebaceous tumours in Muir-Torre syndrome.…”

Complex adnexal tumours of the skin: a report of three cases and review of literature

“…If two or more adnexal tumours are present in a given single clinical lesion, its diagnosis is usually based on the dominant morphological component. However, if no component dominates, they are described under various terminologies such as, combined adnexal tumours, benign adnexal tumours with multidirectional or divergent differentiation, benign adnexal tumours of mixed lineage and composite adnexal tumours 3. Although these complex occurrences are rare, they highlight the difficulties in accurately classifying the skin adnexal tumours.…”