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Invasive SCC present in 31% of SCCIS sent for Mohs surgery

Thirty-one percent of biopsy-proven squamous cell carcinoma in situ lesions sent for Mohs micrographic surgery contained invasive squamous cell carcinoma, according to study data.

In a prospective study, researchers investigated 29 patients (58.6% women) with biopsy-proven squamous cell carcinoma (SCC) in situ (SCCIS) who underwent Mohs micrographic surgery (MMS). The Mohs debulking specimens’ central blocks were horizontally sectioned at 30-mcm intervals. Histologic tumor diagnosis was made by a fellowship-trained Mohs surgeon and a board-certified dermatopathologist.

Nine patients (31% of lesions) had invasive SCC on final histology. Seven others (24%) displayed residual SCCIS; the remaining lesions showed only actinic keratosis (21%) or no residual tumor histologically (24%). Fourteen of the biopsy-proven SCCIS lesions (48.3%) showed clinical evidence of residual tumor, with scales and papular changes. All lesions with invasive SCC displayed residual tumors, compared with 25% of the remaining cases (P<.001). Lesions with invasive SCC were more likely to be greater than 1.4 cm in diameter after being correlated with their final histologic diagnoses.

“A patient with biopsy-proven SCCIS may be presented with treatment options,” the researchers concluded, “including MMS, surgical excision, curettage and fulguration, electrodesiccation, cryotherapy, chemotherapeutic and immune modulating topical creams [5-fluorouracil and imiquimod], photodynamic therapy and laser ablation.

“For lesions that are smaller than 1.4 cm that do not exhibit papular changes or scales, conservative treatment … may be adequate, but for lesions larger than 1.4 cm or with papular changes and scales, surgical excision … is strongly recommended.”