Carcinoma arising in ectopic hamartomatous thymoma. An ultrastructural study

We present the ultrastructural features of a case of adenocarcinoma arising in ectopic hamartomatous thymoma in a 31 year old man, in the supraclavicular location. The tumor had a cribriform adenomatous component with a granular cell quality and mimicked a metastatic carcinoma. Ultrastructurally, the spindle cell component revealed clusters of tonofilaments and the tumor cells were attached by well developed desmosomes. The cytoplasm of adenocarcinoma cells contained peculiar cup-shaped bodies derived from the endoplasmic reticulum wrapped around the mitochondria.