A 41-year-old female presented with an 8.2x4.2 cm left anterior mediastinal mass incidentally detected via computed tomography. She reported some mild night sweats, but no fever or weight loss. Serum beta human chorionic gonadotropin was negative, making germ cell tumors less likely. Follow-up alpha-fetoprotein and anti-acetylcholine receptor antibody were also negative. Fine-needle aspiration revealed benign ciliated epithelioid cells. CT-guided biopsy revealed fragments of ciliated epithelium lining fibrous tissue and cystic contents as demonstrated in the histologic figures below.
What is the most likely diagnosis?
a. Branchial cleft cyst
b. Mature cystic teratoma
c. Thymoma
d. Metastatic cystic squamous cell carcinoma
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Answer to October's Case of the Month.
E. Trypanosoma cruzi
This patient has megacolon of Chagas disease (CD), which is caused by the flagellate protozoan T. cruzi. Chronic infectious megacolon is found in approximately 20 percent of CD patients. The above case had a descriptive pathological diagnosis of fibrosis of the lamina propria, congested blood vessels, hyperganglionosis, neurotization of submucosal and myenteric plexus, and hypertrophy of the muscularis propria. Though this specimen did not show histological changes pathognomonic of CD, its diagnosis can be inferred from the clinicopathologic data and the serologic studies performed prior to surgery. Patients with CD may also develop megaesophagus and many have signs of chronic progressive Chagas cardiomyopathy. Chagas disease is endemic in parts of Brazil, most notably in the states along the Atlantic coast in the east and in the south and southwest regions of the country.
Submitted by Deilson Elgui de Oliveira, Associate Professor of Pathology at UNESP, Faculdade de Medicina de Botucatu, Brazil.
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