The Spectrum of HPV-independent Penile Intraepithelial Neoplasia: A Proposal for Subclassification

Abstract

Compared with vulva, precursor lesions of human papillomavirus (HPV)-independent invasive squamous cell carcinoma (SCC) of the penis are insufficiently characterized. We analyzed the histologic and immunohistochemical characteristics of 70 peritumoral precursor lesions and correlated them with the histology and mutational profile of the adjacent HPV-negative invasive penile SCC. Atypical basal keratinocyte proliferation with variously elongated epithelial rete with premature squamatiziation, but regular superficial cornification, termed differentiated penile intraepithelial neoplasia (d-PeIN), were identified adjacent to 42/70 (60%) SCC (36/42 keratinizing ( P <0.001); 3 papillary, and 1 each verrucous, clear cell, sarcomatoid SCC). d-PeIN were associated with chronic inflammatory dermatoses (32/42; P <0.001), p53 overexpression (26/42; P <0.001), and hotspot mutations in TP53 (32/42; P <0.001), CDKN2A (26/42; P <0.001) or both (21/42; P =0.003) in the adjacent SCC. Cytoplasmic p16 ink4a overexpression in 5/42 d-PeIN correlated with CDKN2A missense mutations in the adjacent SCC. In all, 21/70 (30%) cornified verrucous or glycogenated verruciform precursors with minimal atypia and wild-type p53 (18/21; P <0.001) occurred adjacent to verrucous or papillary SCC (17/21; P <0.001) and keratinizing (4/21) SCC, which harbored mutations in HRAS and/or PIK3CA (12/21; P <0.004). Undifferentiated p16 ink4a -negative full-thickness precursors were identified in 7/70 (10%) SCC. Four histologically different HPV-independent penile precursor lesions can be assigned to 2 major genetic/biological pathways with characteristic highly differentiated precursors requiring different clinical management decisions. These include d-PeIN in chronic inflammatory dermatoses, with p53 overexpression and TP53/CDKN2A mutations, and the p53 wild-type verrucous and verruciform precursors unassociated with dermatoses, but with mutations in oncogenes PIK3CA and HRAS .

FIGURE 1

Differentiated HPV-independent penile precursors (d-PeIN). A, Hematoxylin and eosin–stained section of a d-PeIN adjacent to a keratinizing SCC with TP53 missense mutation and a truncating mutation in CDKN2A revealing elongated and branching rete ridges with premature squamatiziation, mitoses, and mild spongiosis. The dense lichenoid lymphocytic infiltrate is owed to the background of lichen planus. B, Immunohistochemical stain with antibody to p53 reveals focal nuclear overexpression in basal keratinocytes. C, Hematoxylin and eosin–stained section of a d-PeIN with elongated rete and normal cornification adjacent to a keratinizing SCC arising in gylcogenated mucosa without TP53 hotspot mutation but mutations in HRAS and SMARCB1. D, With prominent nuclear overexpression of p53 in basal and suprabasal keratinocytes. E, Hematoxylin and eosin stain of a precursor lesion adjacent to a SCC with a TP53 missense mutation and a trancating mutation in the CDKN2A gene. Note the focally atypical basal cell proliferation with mildly elongated rete ridges, individual mitosis, loss of glycogen but normal maturation and cornification. The basement membrane is focally thickened around pointed rete a dense lymphohistiocytic infiltrate. F, Mildly atypical basal and suprabasal keratinocytes show nuclear p53 over expression.

FIGURE 2

Oncoplot demonstrating characteristics of precancerous lesions including histology, p53 and p16^ink4a overexpression, presence of lichen sclerosus and lichen planus in comparison with p53 and p16^ink4a overexpression and recurrently mutated genes of the adjacent invasive SCC. NA indicates not applicable.

FIGURE 3

A–C, Verrucous acanthotic HPV-independent penile precursors without TP53 hotspot mutations. A, Hematoxylin and eosin–stained section of a massively acanthotic verrucous squamous precursor lesion without TP53 hotspot mutations with absent granular cell layer but thick stacks of parakeratosis and compact hyperkeratosis adjacent to a verrucous SCC with mutations in Notch1, HRAS, and SMAD4. B, The rete ridges are plump and irregularly elongated. C, The plump epithelial rete show minimal atypia, but increased mitotic activity in basal keratinocytes. D–G, Verrucous precancer adjacent to a verrucous SCC with 2 different TP53 missense mutations at low mutational frequency and a truncating mutation in the CDKN2A gene. D, Hematoxylin and eosin stain of verrucous squamous lesion with irregular rete, stacks of para and hyperkeratosis. E, Note the focal circumscribed basement membrane thickening and beginning subepithelial sclerosis with nuclear p53 overexpression of basal keratinocytes. Hematoxylin and eosin stain of another area of verrucous precursor lesion with irregular and elongated rete (F) with wild-type p53 staining of basal keratinocytes (G).

FIGURE 4

Noncornified verruciform and undifferentiated HPV-independent penile precursors. A, Hematoxylin and eosin–stained section of a verruciform noncornified peritumoral lesion of a papillary SCC without TP53 hotspot mutations but an FGFR3 mutation. B, Hematoxylin and eosin stain of another verruciform precursor lesion adjacent to a papillary SCC featuring 2 TP53 missense mutations and a truncating mutation in CDKN2A. Invasive SCC with clear cell differentiation (C) and hotspot mutations in TP53 and CDKN2A had an undifferentiated noncornified peritumoral precursor lesion (D). corresponding nuclear p53 overxpression (E) and weak cytoplasmic p16^ink4a staining (F). G, Hematoxylin and eosin stain of an undifferentiated/basaloid precursor lesion with beginning cornification adjacent to a keratinizing SCC featuring 2 TP53 missense mutations and a PIK3CA mutation. H, but wild-type p53 staining in the peritumoral precursor lesion.

FIGURE 5

Differentiated HPV-independent penile precursors (d-PeIN) with missense mutations in both TP53 and CDKN2A genes. A–D, pT2 SCC, missense mutations in TP53 (R175H) and CDKN2A (P81L). A, Hematoxylin and eosin–stained section: Overview showing the transition of invasive SCC, preinvasive precursor lesion, and lichen planus. B, Nuclear p53 overexpression in the invasive tumor cells and basal and suprabasal cells of the peritumoral precursor lesion. C, Cytoplasmic p16^ink4a overexpression in the invasive tumor cells and basal cells of the peritumoral precursor lesion. D, High-power view of nuclear p53 and cytoplasmic p16^ink4a staining in d-PeIN. E–H, pT2 SCC; missense mutation in TP53 (P278S) and CDKN2A (P114L). Hematoxylin and eosin–stained section: Overview showing the transition of preinvasive precursor lesion to keratinizing invasive SCC arising in chronic lichenoid inflammatory skin disease (E) with nuclear p53 overexpression in the invasive tumor cells and the peritumoral precursor lesion (F). G, The corresponding immunohistochemical stain shows cytoplasmic p16^ink4a overexpression in the invasive tumor cells only. The d-PeIN is negative. High-power view of nuclear p53 overexpression and negative p16^ink4a stain in d-PeIN (H).