Subungual Invasive Squamous Cell Carcinoma with Doubtful Underlying Bone Invasion: A Treatment Proposal

Abstract

<b><i>Introduction:</i></b> Subungual squamous cell carcinoma (sSCC) is the most frequent malignant tumor of the nail unit. When suspecting sSCC, accurate diagnosis is supported by nail biopsy. Depth of invasion and histopathologic signs of human papillomavirus (HPV) infection are related to an unfavorable prognosis. In this case, it is necessary to rule out bone invasion by radiography or MRI, and in case of doubt, amputation is indicated. <b><i>Case Presentation:</i></b> We present 2 cases of sSCC with a confirmatory biopsy of sSCC with HPV and invasion; in both cases, MRI was difficult to distinguish between bone invasion and bone marrow inflammation. Before amputating the distal phalanx, we decided to perform a bone biopsy during the excisional surgery. Neither case required amputation. <b><i>Conclusion:</i></b> We propose that when an invasive sSCC is present and an MRI is doubtful of bone invasion, before amputating, a bone biopsy should be performed.

Update on Squamous Cell Carcinoma of the Nail Unit: An Human Papillomavirus-Associated Condition

“…The proximal nail matrix expresses lower levels of HLA-A/B/C, has fewer CD4+ and CD8+ T cells, and the antigen-presenting capacity of Table 1. Risk stratification of HPV type High-risk 16,18,31,33,35,39,45,51,52,56,58,59,66,11,40,42,43,44,54,61,72,81,89 Classification by carcinogenic risk of alpha HPVs [9]. Bold indicates inclusion in Gardasil-9® vaccine.…”

“…Ideally, an MRI should be performed prior to biopsy. Post-biopsy changes and bone marrow edema may not be distinguishable from bone invasion [45]. In this situation, it has been proposed that for invasive SCCs, a bone biopsy should be performed prior to amputation to prevent unnecessary amputation [45].…”

“…The rate of upstaging nail unit SCC in situ to invasive SCC is not infrequent. Two studies have assessed this issue and identified that 7.7–9.7% of SCC in situ cases were upstaged [46]. It is not clear based on the reported cases if there is an association between upstaging and HPV status.…”