Skin nonmelanocytic tumor

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Contributed by Alessio Giubellino, M.D., Ph.D.

• Skin, right upper cutaneous lip, shave biopsy:
  • Tumor of follicular infundibulum

• Skin, right posterior shoulder, punch biopsy:
  • Benign adnexal neoplasm / benign follicular neoplasm (see comment)
  • Comment: The overall architecture of this tumor is most typical of tumor of follicular infundibulum, although there are also some focal features of trichilemmoma. Clinical correlation and follow up are recommended.

A 54 year old woman presents with a well circumscribed, skin colored plaque on her cheek that has been present for years. She denies spontaneous bleeding from the lesion but she reports a personal history of skin cancer that was removed. A 6 mm punch biopsy was performed. Histopathology reveals interconnected cords of pale staining keratinocytes extending from the epidermis. There is no evidence of acanthosis, peripheral palisading or significant cytologic atypia. Which of the following is the most likely diagnosis?

1. Basal cell carcinoma
2. Clear cell acanthoma
3. Desmoplastic trichoepithelioma
4. Tumor of the follicular infundibulum

D. Tumor of the follicular infundibulum is a benign lesion that can be present for years and is characterized by dense elastic network and abundant pale keratinocytes with notable absence of characteristic features of basal cell carcinoma (BCC). Answer A is incorrect because there is a notable lack of peripheral palisading and cytologic atypia on histology. It is important to note that both tumor of the follicular infundibulum and basal cell carcinoma can have peripheral palisading; however, tumor of the follicular infundibulum does not have basaloid cells but rather pale cells due to glycogen. Answer B is incorrect because although clear cell acanthoma is a benign lesion, it typically presents on the legs and has a pink to brown color or more commonly, is red and shiny. On histology, although clear cell acanthomas have abundant glycogen containing cells, acanthosis is a typical feature. Answer C is incorrect because desmoplastic trichoepithelioma is typically characterized by cords of basaloid cells, often in a dense fibrous stroma. Peripheral palisading is also a common feature on histology.

Comment Here

Reference: Tumor of the follicular infundibulum

Which of the following immunohistochemistry markers would be most helpful in differentiating tumor of the follicular infundibulum with its most common differential?

1. BerEP4
2. CD34
3. CK5/6
4. PDL1

A. BerEP4 is positive in basal cell carcinoma, which is the most common typical differential diagnosis for tumor of the follicular infundibulum. Answer B is incorrect because CD34 is seen in other adnexal tumors and trichoblastoma; however, CD34 would not help to differentiate a basal cell carcinoma from a tumor of the follicular infundibulum. Answer C is incorrect because CK5/6 is positive in squamous cell carcinoma (SCC). Answer D is incorrect because PDL1 is typically used for tumor sensitivities in melanoma, not for differentiating a basal cell carcinoma.

Comment Here

Reference: Tumor of the follicular infundibulum

A patient presenting with multiple eruptive tumors displaying the histologic features shown above should be evaluated for which of the following?

1. Bowen disease
2. Cowden syndrome
3. Grover disease
4. Tuberous sclerosis

B. Cowden syndrome is associated with the presentation of infundibulomas. Answer A is incorrect because there is no known association between Bowen disease and infundibulomas. The image shows plate-like, reticulated proliferation of keratinocytes that are branching from the epidermis and anastomosing in the reticular dermis, which is characteristic of TFI. Answer C is incorrect as there is no known association of Grover disease with TFIs. Additionally, the image does not show focal acantholysis, which is characteristic of Grover disease. Answer D is incorrect because tuberous sclerosis is not associated with TFIs. While tuberous sclerosis may present as hypopigmented macules on the skin similar to TFIs, they are the result of simple depigmentation rather than benign neoplastic growths arising from the hair follicle infundibulum.

Comment Here

Reference: Tumor of the follicular infundibulum