Non-Melanoma Skin Cancers Coverage from Every Angle

Depth of Follicular Involvement in Invasive Squamous Cell Carcinoma

By: Susan Reckling
Posted: Wednesday, August 22, 2018

Although previous studies have shown that follicular extension is usually superficial in bowenoid actinic keratosis, a new Spanish study may suggest otherwise. In a report published in the Journal of the European Academy of Dermatology and Venereology, Fernández-Figueras et al reported that actinic keratoses may show extension down into the follicles—not only in cases of full-thickness epidermal atypia (bowenoid actinic keratosis) but also in cases with atypia limited to the epidermal basalis.

The investigators examined the relationship between follicular extension of atypical keratinocytes in an actinic keratosis and the development of invasive squamous cell carcinoma from the follicular wall. The depth of follicular extension was correlated with the depth of invasion of squamous cell carcinoma. A total of 193 biopsy specimens of invasive squamous cell carcinoma with an associated actinic keratosis underwent retrospective histologic review.

Follicular extension was present in about one-quarter of cases (25.9% of 50 cases), and it usually extended into the lower follicular segment. As for invasive squamous cell carcinoma, it was found to be directly adjacent to the follicular basalis in more than half of cases (58% of 29 cases); it appeared to correlate highly with the depth of follicular extension (infundibular, 3 of 12; isthmic, 21 of 33; subisthmic, 5 of 5).

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