Frozen Section Shows Inflammation at the Margin
You are performing Mohs surgery on a 74-year-old woman with a 2.0 cm morpheaform basal cell carcinoma of the left medial canthus. After the first stage, the cryostat sections show dense lymphocytic infiltrate and fibrosis at the deep margin, but no unequivocal tumor islands. The histotechnician notes the block is slightly thick and there is a fold in one quadrant of the section. The patient is anxious and asks if "it's all gone." The defect currently measures 1.8 x 1.5 cm and the medial canthus is distorted.
1. How do you interpret this frozen section, and what are your next steps before declaring a clear margin?
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A dense lymphocytic infiltrate and fibrosis with no definite tumor is not a reliable negative in a morpheaform BCC, which characteristically grows as thin cords and single cells within fibrous stroma and can be mimicked or obscured by inflammation and scar. Two technical problems compound the uncertainty: a thick block and a folded section in one quadrant mean part of the margin was not adequately evaluated. The correct response is not to call it clear. Options: (1) ask the histotechnician to recut thinner sections and eliminate the fold, and re-examine the entire mapped margin; (2) if tumor cannot be excluded, take an additional Mohs stage from the area of concern (the deep margin and the folded quadrant) to obtain interpretable tissue; (3) consider immunohistochemistry (e.g., Ber-EP4 or anti-BCL2) on formalin-fixed tissue if frozen interpretation remains equivocal, accepting a delay. Only after complete, artifact-free margin review with no tumor do you declare clearance. Tell the patient honestly that the first look is inconclusive and that you are taking another layer to be certain - this is the value of Mohs.
2. If the margin ultimately requires a second stage, how does that change your reconstruction planning at the medial canthus?
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Each additional stage enlarges the defect and may involve the medial canthal tendon, lacrimal system, or periorbital skin, so reconstruction must be planned for the final defect, not the first. Steps: measure and map the final defect; assess canthal tendon integrity and lacrimal drainage (probing if the canaliculus is at risk); if the tendon is detached, plan reattachment (e.g., to the periosteum or with a canthal strip) to prevent lateral canthal dystopia and epiphora. For a medial canthal defect of this size, options include a glabellar or nasolabial transposition flap, a full-thickness skin graft (with the caveat of poorer color match and possible contracture), or a combination; avoid tension that would displace the canthus. Consider delaying repair 24-48 hours if margin clearance required multiple stages or if the defect is complex, and coordinate with oculoplastics if the lacrimal system is involved. Document the plan and the patient's consent for possible staged reconstruction.