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.

The importance of reviewing pathology specimens before Mohs surgery.

Background: The review of outside biopsy slides before performing surgery is the standard of care in many surgical specialties. Previous studies have shown high discrepancy rates between the original and second-opinion diagnoses. The frequency with which this practice changes the diagnosis and management of patients undergoing Mohs surgery is undocumented in the literature.

Elastosis perforans serpiginosa.

A 41-year-old white man with Down syndrome presented with a slightly pruritic, papular eruption on bilateral forearms of several years' duration. Physical examination revealed multiple 2- to 3-mm keratotic, umbilicated pink papules in an annular configuration distributed symmetrically on the flexural surfaces of the forearms (Figure 1). The skin surrounding these papules was noted to be hyperpigmented and somewhat atrophic.

Combined Merkel cell carcinoma and atypical fibroxanthoma.

Background: Although there are reports of squamous cell carcinoma arising within and adjacent to Merkel cell carcinoma, and one report of an atypical fibroxanthoma-like tumor arising in an irradiated recurrent Merkel cell carcinoma, there have previously been no reports of an immunohistochemically verified atypical fibroxanthoma occurring in conjunction with a Merkel cell carcinoma.

Objective: We report on a neoplasm with distinct features of both Merkel cell carcinoma and atypical fibroxanthoma.

Methods: Histologic and immunohistochemical evaluations were performed.

Merkel cell carcinoma.

Merkel cell carcinoma is an aggressive tumor that should be treated early and aggressively. Although there are 5 published cases of spontaneous regression of Merkel cell carcinoma, a patient's best chance for survival is early detection with either wide local excision or Mohs' micrographically controlled margins with a final 5- to 10-mm layer. This should be followed by sentinel lymph node biopsy with lymph node dissection of the draining basin if metastases are discovered.

White piedra: further evidence of a synergistic infection.

White piedra is a fungal infection of the hair shaft caused by Trichosporon beigelii. A synergistic coryneform bacterial infection is often present with T beigelii. White piedra, although not commonly reported to infect scalp hair in North America, is an important consideration in the differential diagnosis of scalp hair concretions.