Mohs frozen tissue sections in comparison to similar paraffin-embedded tissue sections in identifying perineural tumor invasion in cutaneous squamous cell carcinoma.

BACKGROUND: Perineural invasion (PNInv) in cutaneous squamous cell carcinoma (cSCC) increases the risk of recurrence, possibly because of suboptimal identification on frozen or paraffin-embedded tissue sections. Perineural inflammation (PNInf) may portend PNInv. OBJECTIVE: We sought to correlate identification of PNInv and PNInf in hematoxylin-eosin-stained Mohs frozen sections with PNInv and PNInf identified in similarly oriented paraffin-embedded sections obtained in cases of cSCC. METHODS: We reviewed same patient Mohs frozen and paraffin-embedded tissue sections for all patients presenting within a 2-year period to our Mohs micrographic surgical unit for removal of cSCC with PNInv or PNInf identified on either type of tissue section. RESULTS: Of 537 patients undergoing surgical resection of cSCC, 21 (3.9%) had either PNInv (n = 11) or PNInf (n = 10) on frozen sections. PNInv on Mohs frozen sections was identified in 11 cases and confirmed on paraffin-embedded sections in 9 cases (82%). Paraffin-embedded sections failed to identify PNInv present in Mohs frozen sections in two (2/11), or 18% of cases. PNInf on Mohs frozen sections was confirmed on paraffin-embedded sections in 3 cases (30%), but PNInv was identified in 5 cases (50%). LIMITATIONS: Our results are a retrospective case review from a specific time period by one institution. Furthermore, it is impossible to compare identical tissue specimens using two sequential tissue processing techniques. CONCLUSION: PNInv can be accurately identified with Mohs frozen sections. PNInf on Mohs frozen sections suggests the presence of PNInv and requires further histologic investigation.

Keloid formation occurring in the distribution of a congenital vascular malformation.

A 35-year-old African American man presented with complaints of malodorous drainage from hypertrophic lesions on his occipital scalp (Figure 1, inset). The patient had no family history of keloid formation and no other keloids on his body. The hypertrophic mass on his scalp had been present for 10 years and had not been a result of any type of mechanical, surgical, or laser treatment. It corresponded to the distribution of a large vascular malformation over the occiput (Figure 1). The vascular malformation extended from the occipital scalp to the right parietal scalp, the right side of the face, neck, upper chest, and right arm, with varicosities and hypertrophy of the right upper extremity (Figure 2). The vascular malformation over the right parietal scalp and ear was characterized by bleb formation and hypertrophy of the right ear. The patient reported that no manipulation, including laser treatment, of the vascular malformation had been previously performed. He did state that a previous dermatologist had attempted serial surgical excision of the cerebriform nodules but retired during the course of treatment. He stated that the appearance of his keloid formation and port-wine stain had not changed during the past 10 years. A previous biopsy of a hypertrophic lesion showed histologic findings consistent with folliculitis keloidalis nuchae. Cephalexin 500 mg 4 times daily for 14 days was prescribed for the purulent drainage. A Doppler ultrasound was ordered of the right upper extremity to evaluate for an arteriovenous malformation and showed no evidence of venous thrombosis or arteriovenous malformation. On a second visit 2 weeks later, the hypertrophic lesions continued to show drainage. Clindamycin gel to be applied twice daily to the scalp was added. The patient also had magnetic resonance imaging with and without gadolinium contrast (Figure 3) ordered, which showed a large hypertrophic giant scalp keloid overlying the occipital and suboccipital region measuring 12x 19 cm. There was soft tissue thickening involving the right external ear, extending inferior to the right ear, overlying an intact parotid gland. There was no evidence of muscular or skull invasion.