E. 2008. Pulmonary atresia with intact ventricular septum (PA-IVS) in monozygotic twins. Am J Med Genet Part A 146A:525-528. To the Editor:Pulmonary atresia with intact ventricular septum (PA-IVS) is a rare congenital heart defect (CHD) of unknown etiology, characterized by an atretic pulmonary valve with the right ventricle varying in size and morphology among different affected individuals. We report on monozygotic (monochorionic diamnionic) twin sisters with PA-IVS who died soon after birth. The patients were prematurely born at 27 weeks by caesarean to a 24-year-old gravida 1, para 0 Hispanic mother. The pregnancy course was previously uneventful, and the mother denied any exposures during pregnancy. Both parents were healthy, nonconsanguineous, with no known family history of CHD in a three-generation pedigree. The Apgar scores were 5 and 7 (Twin A), and 4 and 6 (Twin B), at 1 and 5 min, respectively. Birth weight was 1,050 g (60th centile, Twin A) and 910 grams (40th centile, Twin B), crown-heel length was 35 cm for both twins, and occipital-frontal circumferences were 24.8 cm (Twin A) and 25 cm (Twin B). Soon after birth, Twin A developed increasing respiratory rate requiring mechanical ventilation, and a systolic ejection murmur at the left upper sternal border was noted accompanied by poor oxygen saturations. Chest X-ray revealed hazy, granular lung fields consistent with hyaline membrane disease as well as a cardiac silhouette occupying nearly 70% of the thoracic diameter. An echocardiogram revealed an annular-type pulmonary valve atresia, and aortic stenosis with a bicuspid aortic valve. The left ventricle appeared normal in size and function. In spite of therapy, the patient developed respiratory failure and died at the age of 3 days. Twin B had a similar clinical course and the echocardiogram also showed pulmonary valve atresia (without aortic atresia), suprasystemic right ventricular systolic pressures and moderate tricuspid regurgitation. On day 3 of life, the echocardiogram showed poor cardiac function with left ventricular ejection fraction of 45%. Grade IV germinal matrix hemorrhage was detected by ultrasound. Comfort care was provided, and she died on day 7 of life. Unrestricted postmortem examinations, following perinatal autopsy protocols were performed in both patients.The cardiac findings present in both twins were virtually identical, consistent with the diagnosis of PA-IVS, and characterized by cardiomegaly Twin A: 16.5 g; Twin B: 15.2 g), marked right atrial dilatation, marked right ventricular myocardial hypertrophy (8-10 mm in thickness) and a small right ventricular chamber measuring approximately 9 mm from the atrioventricular annulus to the apical aspect of the chamber. In both cases, the tricuspid valves were dysplastic with two identifiable thick leaflets, attached to the right ventricular endocardium through markedly short and thickened chorda tendineae and papillary muscles. The pulmonary valve was completely atretic in both patients, with three fused valves leaving no identifi...

Our work demonstrates that MYC expression levels differ between these 2 histologic mimics and suggests that this important oncoprotein may play a role in the pathogenesis of SPTCL.

Spitz nevi are acquired melanocytic lesions with a wide histomorphological spectrum; reliable distinction from spitzoid melanoma is often difficult. Misdiagnoses of benign spitzoid tumors as spitzoid melanomas and vice versa are attributable to a frequently disturbing morphology and inconsistent or poorly defined histological criteria for diagnosis. Many recognized histological variants of Spitz nevi have been described, including the intradermal Spitz. Histopathologic descriptions of intradermal Spitz nevi have been done in the past; however, large studies addressing their histological spectrum have been lacking. We have retrospectively assessed the morphological features in 74 cases of intradermal Spitz nevi, excluding tumors clearly defined as atypical Spitz nevi and Spitzoid melanomas, to further delineate their histological spectrum. The patients' ages ranged from 5 to 81 years (median: 27). Anatomic location included: the upper extremities (27 cases), followed by head and neck (22 cases), lower extremities (9 cases), back (8 cases), buttock (5 cases), chest (1 case), and vulva (1 case). In 1 case, the anatomic location of the lesion was not available. Different histological variants were observed including hyalinized, polypoid, desmoplastic, angiomatoid, and halo Spitz. Morphological features evaluated included symmetry (100%), cell type (epithelioid 42%, spindle 16%, mixed 42%), maturation (85%), pigmentation (26%), chronic inflammation (24%), and mitotic activity (38%). Mild atypia was seen in 36 cases (49%), moderate atypia was seen in 28 cases (38%), and severe atypia was seen in 10 cases (14%). Intradermal Spitz nevus is a distinctive type of Spitz nevus that sometimes can be difficult to define given the unusual features that these lesions can show; thus, strict application of well-defined histological criteria and awareness of their morphological spectrum will facilitate definitive diagnosis.