18
cytology of Soft Tissue, Bone, and Skin
such as papillary carcinoma of the thyroid may come into the
differential diagnosis if too much emphasis is placed on the
longitudinal grooves of the osteoblasts and other distinguishing
features are overlooked. This tumor is characterized by the pres-
ence of primitive chondroblasts, multinucleated osteoclastic
giant cells, and chondroid matrix.
Key features of chondroblastoma
• Poorly cohesive groups or single cells;
• Metachromatic or fibrillar matrix;
• Mononucleated primitive cells;
• Longitudinal nuclear grooves; and
• Giant cells.
chondrosarcoma
These malignant tumors arise mostly in bone, but sometimes
in soft tissue. They do not produce osteoid or bone, but rather a
chondroid matrix. The pelvis, more specifically the acetabulum,
Fig. 18.28 Chondroma. Individual cells of a benign cartilaginous lesion
(chondroma). The cells are round without obvious nucleoli. Binucleation is
not seen. The background matrix is abundant (May-Grunwald-Giemsa x HP).
Fig. 18.29 Chondrosarcoma. Low-grade chondrosarcoma. Note the lack
of pleomorphism (May-Grunwald-Giemsa x HP).
is a frequent site of occurrence as is the proximal femur and
proximal humerus. Unlike chondroblastoma, the location of
chondrosarcomas in the bone is diaphyseal or metaphysical.
These tumors are aggressive and destructive and grow through
bone into soft tissue. They are graded from grade I to III and
grading is important in treatment and prognosis. The histologic
grade of chondrosarcomas is related to the cytologic appearance
and very well differentiated grade I chondrosarcomas may not
be easily recognized as malignant in FNAB material (Fig. 18.28).
The cellularity of malignant chondroid neoplasms is generally
greater than in benign neoplasms but sampling plays a role in
FNABs.
In classic chondrosarcomas, lower grade, the cytology smear
shows cells in lacunae in a cartilaginous matrix (Fig. 18.29). The
cells may be unevenly dispersed, crowded, and binucleated. The
nuclei are rounded and centrally placed and nucleoli may be
prominent (Fig. 18.30). Cells have round, well-defined borders
and pale cytoplasm. The cartilaginous matrix is bright magenta
in Giemsa-stained smears (Fig. 18.31). The grading increases
with increasing cellularity; low- and high-grade tumors can
usually be separated in FNAB material (Figs. 18.32, 18.33).
Chondrosarcomas are classified as dedifferentiated, mesen-
chymal, myxoid, and clear cell. Overt cellular pleomorphism
is generally not a feature of chondrosarcomas, except in dedif-
ferentiated tumors. In dedifferentiated chondrosarcoma classic
low-grade elements are seen intermixed with undifferentiated
sarcomatoid elements. An FNAB may only yield the cells of
poorly differentiated sarcoma and the diagnosis of chondrosar-
comas may be missed.
Mesenchymal chondrosarcomas are aggressive tumors found
in younger patients and arise most often in bone, not soft tis-
sue. The jaw and ribs are most often affected. Metastases to
lung are frequent. Cytology specimens are highly cellular with
foci of cartilage mixed with hyperchromatic small round blue
cells with a high N/C ratio and coarse chromatin. Unlike Ewing
sarcoma, the cells of mesenchymal chondrosarcoma are PAS
negative. Osteoclast-like giant cells may also be present. Calci-
fication and ossification, along with necrosis and hemorrhage,
also occur.149
Myxoid chondrosarcoma is considered a low-grade malig-
nancy. It is a slow-growing, well-delineated tumor that may be
Fig. 18.30 Chondrosarcoma. FNAB of a single cell from a chondrosarcoma
showing a centrally placed round nucleus in a lacuna (Papanicolaou x HP).
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