Rare Benign and Low Malignant Potential Tumors

Michael J. Thrall, MD

Key Facts

Clinical Issues

Hamartoma results from overgrowth of mature mesenchymal elements
Sclerosing hemangioma arises from pneumocytes though lesions resemble vascular tumors
Solitary fibrous tumor usually arises from pleura but may arise elsewhere and is not always single
Clear cell (sugar) tumor arises from perivascular epithelioid cells (PEComa)

Cytopathology

Hamartoma consists of mixed benign stromal and glandular elements
Sclerosing hemangioma neoplastic pneumocytes form loose clusters surrounding stromal cores
Solitary fibrous tumor features bland spindle cells with collagen in background
Clear cell (sugar) tumor consists of bland cells with abundant finely vacuolated glycogen-rich cytoplasm

(A) Aspiration of a pulmonary hamartoma will yield mixed benign mesenchymal

and epithelial

elements, as seen in this Pap stain. (B) A closer view from the same case highlights the fibrillary appearance of the cartilaginous matrix

. (C) The surface cells of sclerosing hemangioma form loose clusters with fine chromatin, seen here in an H&E touch preparation. Nuclear contour irregularities, including pseudoinclusions