The histological discrimination between desmoplastic trichoepithelioma, infiltrative basal cell carcinoma, and microcystic adnexal carcinoma encountered in small biopsies is challenging when only morphological criteria are applied. The objective of this study is to test the use of p75 neurotrophin receptor (p75NTR) as an adjunct aid in classification of these tumors. Immunohistochemistry for p75NTR antigen was performed on routinely processed biopsies of 37 desmoplastic trichoepitheliomas, 11 infiltrative basal cell carcinomas, and 9 microcystic adnexal carcinomas diagnosed by morphological criteria in conjunction with results of CK20 immunostains. Cases were analyzed for the extent and intensity of p75NTR expression. Diffuse immunoreactivity was defined as involving >90% of tumor cells. Of the 37 desmoplastic trichoepitheliomas, 35 (94%) displayed strong diffuse immunoreactivity of tumor cells, proving high sensitivity of the marker to detect this tumor. However, despite the fact that diffuse p75NTR expression reached statistical significance in differentiating desmoplastic trichoepithelioma from infiltrative basal cell carcinoma (Fisher exact test P < 0.0001) and microcystic adnexal carcinoma (P < 0.0016), specificity of the stain is unsatisfactory because strong diffuse expression of p75NTR by neoplastic cells was observed in 4 (36%) cases of infiltrative basal cell carcinomas and 4 (44%) cases of microcystic adnexal carcinoma. This study demonstrates a significant difference in p75NTR expression in selected sclerosing neoplasms of the skin. Nevertheless, the practical value of p75NTR as an adjunct marker in the differential diagnosis of these tumors seems to be limited because of significant overlap in amount of p75NTR immunoreactivity.

Primary carcinoid tumor of the skin (PCTS) is an uncommon indolent neoplasm, with 10 cases described in the literature. The tumors affect patients in the sixth to ninth decades of life (mean = 66.3 years) with an equal gender distribution and predilection for the head and trunk. They present as slowly enlarging nodules of variable duration, ranging from 1 to 60 years (mean = 11.4 years). PCTS is characterized by architectural, cytomorphologic, ultrastructural, and immunohistochemical features typical of a low-grade neoplasm with neuroendocrine differentiation. PCTS typically follows a benign clinical course and therefore has to be distinguished from cutaneous metastases of visceral carcinoid tumors, which herald dissemination of malignancy and poor prognosis. While the distinction from other histologically similar entities can be achieved by histopathological examination, PCTS can be distinguished from a visceral metastasis only by a judicious clinicopathologic correlation. Herein we describe the clinical presentation, histological appearance, and management of these tumors.

Patients with relapsed classic Hodgkin lymphomas (cHLs) receive salvage therapy with immune checkpoint inhibitors (ICIs) or chemotherapy (no-ICI). Patients responding to therapy often undergo consolidation with allogeneic blood or marrow transplantation (alloBMT). We previously reported that relapsed patients with cHL treated with ICI followed by alloBMT experienced improved 3-year progression-free survival (PFS) compared with patients treated with salvage chemotherapy without ICI followed by alloBMT. In this retrospective analysis, we report the 5-year overall survival (OS), PFS, and graft-versus-host disease (GVHD) incidence in patients with cHL treated with ICI before alloBMT with post-transplantation cyclophosphamide GVHD prophylaxis. Among the 147 relapsed/refractory patients with cHL, 71 (48.3%) received ICIs and 76 (51.7%) received chemotherapy without ICIs (no-ICI) before alloBMT. We observed an improved 5-year estimated OS of 91% (ICI) vs 66% (no-ICI; hazard ratio [HR], 0.39; 95% confidence interval [CI], 0.16-0.98; P = .046) and a 5-year estimated PFS of 84% (ICI) vs 53% (no-ICI; HR, 0.4; 95% CI, 0.2-0.81; P = .011). The 12-month cumulative incidence of grade 3 to 4 GVHD was 20% (ICI) and 7% (no-ICI; subdistribution hazard ratio (SDHR), 3.16; 95% CI, 1.13-8.81; P = .03). More frequent grade 3 to 4 acute GVHD was likely due to the higher incidence of grade 3 to 4 acute GVHD in the subset of patients with pretransplant exposure to ICI and shortened duration (60 days) of immunosuppression vs patients with long immunosuppression (day 180). These data suggest that patients with cHL treated with ICI and alloBMT experience improved OS, and the GVHD risk can be mitigated by immunosuppression until day 180.