We report a case of cutaneous squamous cell carcinoma (CSCC), initially coexisting with invasive extramammary Paget's disease (EMPD), in the scrotum of an 84‐year‐old man. The patient initially had a rash and pruritus before presenting with a pedunculated scrotal mass surrounded by widespread erythema. He underwent total gastrectomy for adenocarcinoma 1 year previously and had been receiving TS‐1 (Tegafur/Gimeracil/Oteracil pottasium) orally. Histopathologically, the tumor consisted of invasive SCC, with invasive EMPD in the erythematous region. From the clinical presentation and histopathological findings, we assumed that CSCC developed in the background of the EMPD. The CSCC metastasized to several inguinal lymph nodes and to the brain in the following years. While the histogenesis of each of the tumors remains to be elucidated, the fact that the CSCC rather than the EMPD metastasized to a distant site in this patient is to be noted for future treatment considerations.

Background Alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV) is a rare disorder of pulmonary vascular abnormality with persistent pulmonary hypertension of the newborn. The symptom usually presents within hours after birth, leading to an early demise. Heterozygous de novo point mutations and genomic deletions of the FOXF1 (forkhead box F1) gene or its upstream enhancer have been identified in most patients with ACD/MPV. Most cases of ACD/MPV are sporadic; however, familial cases are also reported in 10% of patients. Case presentation We herein report a case of familial ACD/MPV that showed unusual glomeruloid proliferation of endothelial cells. In this family, three of the four siblings died within two to 3 days after birth because of persistent pulmonary hypertension and respiratory failure. Only the second child remains alive and healthy. An autopsy was performed for the third and fourth children, resulting in a diagnosis of ACD/MPV based on the characteristic features, including misalignment of smaller pulmonary veins and lymphangiectasis. In both of these children, glomeruloid endothelial proliferation of vessels was noted in the interlobular septa. The vessels were immunohistochemically positive for D2–40, CD31, Factor VIII, and ERG, suggestive of differentiation for both lymphatic and blood vessels. Conclusions Unusual glomeruloid endothelial proliferation was observed in a familial ACD/MPV case. This histologic feature has not been described previously in ACD/MPV or any other pulmonary disease. Although the histogenesis of this histologic feature is unclear, this finding may suggest that ACD/MPV is a compound vascular and lymphovascular system disorder that exhibits various histologic features.