Squamous intraepithelial lesions of the anal squamocolumnar junction: Histopathological classification and HPV genotyping

Abstract

Background: Human papillomavirus (HPV)-related anal cancer lesions are often found adjacent to the squamocolumnar junction (SCJ). We have assessed the histopathology and associated HPV genotypes in anal SCJ lesions in surgically excised anal warts in HIV-negative and -positive patients.

Methods: Histopathology identified 47 squamous intraepithelial lesions (SILs) adjacent to the SCJ amongst a total of 145 cases of clinically diagnosed anal condylomata. The anal SCJ lesions were further analyzed with p16, CK7 and p63 immunohistochemistry and HPV genotyping.

Results: Sixteen (16/47) of the excised anal wart lesions contained HSIL; Three were HSIL and exclusively associated with oncogenic HPVs. A further thirteen (13/47) were mixed lesions. Of these eight were HSILs with LSIL and six were HSILs with papillary immature metaplasia (PIM); Ten of the mixed lesions were associated with one or more oncogenic HPVs, while three cases were exclusively associated with HPV6.

Conclusions: Clinically diagnosed anal warts cannot be assumed to be limited to low-grade lesions as anal warts of the SCJ often show heterogeneous lesions, with coexistence of LSIL, PIM, and HSIL. Lesions showing PIM, however, may mimic HSIL, because they are hypercellular, but lack the nuclear atypia and conspicuous mitotic activity of HSIL; and are p16 negative.

Keywords: Anal squamocolumnar junction; HIV; HPV; High-grade squamous intraepithelial lesion (HSIL); Low-grade squamous intraepithelial lesion (LSIL); Papillary immature metaplasia (PIM).

Fig. 1

Schematic diagram of the 47 FFPE anal squamous intraepithelial lesion (SIL) cases of the squamocolumnar junction (SCJ).

Fig. 2

SIL of the anal SCJ showing coexistence of LSIL and HSIL in a HIV-positive patient: A) Hematoxylin-eosin staining. LSIL is exophytic, while HSIL is limited to a flat area; B) Strong and diffuse local p16 immunostaining in the HSIL component but only patchy staining in the LSIL component of the lesion; C) Nuclear p63 immunostaining. HPV genotyping was positive for HPV6. Original magnification x4.

Fig. 3

SIL of the anal SCJ showing coexistence of PIM, LSIL and HSIL in a HIV-positive patient: A) Hematoxylin-eosin staining; B) Strong and diffuse local p16 immunostaining limited to HSIL component of the lesion; C) Strong nuclear p63 immunostaining. HPV genotyping was positive for HPV6 and HPV16. Original magnification x4.

Fig. 4

HSIL of the anal SCJ showing increased cellularity, and loss of surface maturation: A) Hematoxylin-eosin staining with 10 x original magnification; B) Higher magnification showing increased nuclear-cytoplasmic ratio and abnormal mitosis. Hematoxylin-eosin staining with 40 x original magnification; C) Negative p16 immunostaining, 20 x original magnification; D) Positive CK7 immunostaining, 40 x original magnification; E) Nuclear p63 immunostaining, 40 x original magnification. HPV genotyping was positive for HPV52 and HPV91.

Fig. 5

SIL of the anal SCJ showing LSIL, and contiguous area of PIM: A) SIL of the anal SCJ showing LSIL, and contiguous area of PIM. Original magnification x4; B) The area of PIM is densely cellular compared with LSIL. Original magnification x10; C) Negative p16 immunostaining, 20 x original magnification; D) PIM showing papillae with thin fibrovascular cores lined by stratified epithelium with columnar cells on the surface. Significant nuclear atypia or mitotic activity was not observed. Original magnification x20; E) Columnar cells on the surface of papillae were CK7 positive. Original magnification x20. HPV genotyping was positive for HPV6.