Page 883 - Textbook of Pathology, 6th Edition

3. Round cell liposarcoma is composed of uniform, round Histologically, the tumour cells have resemblance to 867
to oval cells having fine multivacuolated cytoplasm with embryonal stage of development of muscle fibres. There
central hyperchromatic nuclei. Round cell liposarcoma is considerable variation in cell types. Generally, the
may resemble a signet-ring carcinoma but mucin stains tumour consists of a mixture of small, round to oval cells
help in distinguishing the two. and spindle-shaped strap cells having tapering bipolar
4. Pleomorphic liposarcoma is highly undifferentiated and cytoplasmic processes in which cross-striations may be
the most anaplastic type. There are numerous large evident. The tumour cells form broad fascicles or bands.
tumour giant cells and bizarre lipoblasts. Mitoses are frequent.
The prognosis of liposarcoma depends upon the location 2. BOTRYOID RHABDOMYOSARCOMA. Botryoid
and histologic type. In general, well-differentiated and variety is regarded as a variant of embryonal rhabdomyo-
myxoid varieties have excellent prognosis, while sarcoma occurring in children under 10 years of age. It is
pleomorphic liposarcoma has significantly poorer prognosis. seen most frequently in the vagina, urinary bladder and nose
Round cell and pleomorphic variants metastasise frequently (page 724).
to the lungs, other visceral organs and serosal surfaces.
Grossly, the tumour forms a distinctive grape-like
SKELETAL MUSCLE TUMOURS gelatinous mass protruding into the hollow cavity.
Histologically, the tumour grows underneath the muco-
Rhabdomyoma and rhabdomyosarcoma are the benign and sal layer, forming the characteristic cambium layer of
malignant tumours respectively of striated muscle. tumour cells. The tumour is hypocellular and myxoid with
predominance of small, round to oval tumour cells
RHABDOMYOMA (Fig. 29.9).
Rhabdomyoma is a rare benign soft tissue tumour. It should
not be confused with glycogen-containing lesion of the heart 3. ALVEOLAR RHABDOMYOSARCOMA. Alveolar type
designated as cardiac rhabdomyoma which is probably a of rhabdomyosarcoma is more common in older children and
hamartomatous lesion and not a true tumour. Soft tissue young adults under the age of 20 years. The most common CHAPTER 29
rhabdomyomas are predominantly located in the head and locations, unlike the embryonal variety, are the extremities.
neck, most often in the upper neck, tongue, larynx and Grossly, the tumour differs from embryonal type in arising
pharynx.
directly from skeletal muscle and grows rapidly as soft
Histologically, the tumour is composed of large, round and gelatinous mass.
to oval cells, having abundant, granular, eosinophilic Histologically, the tumour shows characteristic alveolar
cytoplasm which is frequently vacuolated and contains pattern resembling pulmonary alveolar spaces. These
glycogen. Cross-striations are generally demonstrable in spaces are formed by fine fibrocollagenous septa. The
some cells with phosphotungstic acid-haematoxylin tumour cells lying in these spaces and lining the fibrous
(PTAH) stain. The tumour is divided into adult and foetal Soft Tissue Tumours
types, depending upon the degree of resemblance of
tumour cells to normal muscle cells.

RHABDOMYOSARCOMA
Rhabdomyosarcoma is a much more common soft tissue
tumour than rhabdomyoma, and is the commonest soft tissue
sarcoma in children and young adults. It is a highly malignant
tumour arising from rhabdomyoblasts in varying stages of
differentiation with or without demonstrable cross-striations.
Depending upon the growth pattern and histology, 4 types
are distinguished: embryonal, botryoid, alveolar and
pleomorphic.
1. EMBRYONAL RHABDOMYOSARCOMA. The
embryonal form is the most common of the rhabdo-
myosarcomas. It occurs predominantly in children under 12
years of age. The common locations are in the head and neck
region, most frequently in the orbit, urogenital tract and the
retroperitoneum.

Grossly, the tumour forms a gelatinous mass growing
between muscles or in the deep subcutaneous tissues but Figure 29.9 Botryoid rhabdomyosarcoma, nose. The tumour shows
generally has no direct relationship to the skeletal muscle. the characteristic submucosal Cambium layer of tumour cells. The tumour
cells are round to oval and have anaplasia.