18
cytology of Soft Tissue, Bone, and Skin
Fig. 18.45 Chordoma. (A) Histologic section. Large cells with vacuolated cytoplasm (physaliphorous cells) in nests, cords, or sheets embedded within a
myxoid stroma (H&E x MP). (B) Smear. Large, mono- or binucleated physaliferous cells with vacuolated cytoplasm, centrally located nuclei, granular chromatin
pattern, and small nucleoli. Metachromatic staining of background fibrillary matrix which surrounds individual cells (May-Grunwald-Giemsa x MP).
Fig. 18.46 Adamantinoma. Adamantinoma of long bone. The FNAB shows tight characteristic clusters of cells with peripheral palisading. The central cells
are more squamoid and are arranged in nests. The tissue section corresponds very well to the cytology appearance (H&E x MP).
Epithelial Tumors
Epithelioid and Epithelial Neoplasms of Bone
Epithelioid and epithelial neoplasms seen in bone are rare and
include epithelioid variants of vascular lesions, osteoblastoma,
osteosarcoma, chordoma, and chondroblastoma as well as
adamantinoma and metastatic carcinoma.
The differential diagnosis in epithelioid/epithelial lesions of
bone is limited. The main consideration in many cases is distin-
guishing primary from metastatic lesions.181
Adamantinoma
Adamantinoma is an unusual low-grade malignant neoplasm
of bone. It most commonly occurs in young people and the
vast majority arise in the tibia, with the fibula, or both bones,
sometimes affected.182 This is a lytic lesion that involves the
diaphysis of bone and the affected portion of bone appears
expanded by the tumor. Positive keratin stains support the epi-
thelial nature of this tumor. The malignant epithelial cells are
found in a stroma of fibrous tissue and scattered fibroblasts. The
cells are arranged in strands and nests and appear homogeneous
with bland nuclei. Squamoid-like nest may be present and can
be keratinized. Mesenchyme may also be present.183 The N/C
ratio is high, the nuclear chromatin is rather fine, and nucleoli
are not easily found. The clusters of cells may show peripheral
palisading (Fig. 18.46). This tumor can be mistaken for a meta-
static carcinoma to bone. The bland nuclear appearance and the
age of the patient are helpful in ruling out metastases from an
unknown primary.
Adamantinomas also arise from tooth-forming structures
and are then categorized as odontogenic tumors.
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