• Myofibers in longitudinal section.
Striations produced by the sarcomeres
are clearly visible.
•One of the earliest signs of myofiber
necrosis is the loss of these striations.
The common sites are posterior
portion of the tongue, followed by
palate, cheeks, gingiva, lips and
Oral lesions are slow growing,
painless, often pedunculated
Central leiomyoma are rare-
Bundles or fascicles of spindled cells with eosinophilic and
possibly fibrillary cytoplasm
Nuclei are blunt ended and elongated with fine chromatin,
indistinct nucleolus and variable cytoplasmic vacuole at one end
Bundles of fibres appear to form WHORLS because of their
fascicular arrangement in varying planes.
Few mitotic figures 5/30/2023
25. CLINICAL FEATURES
Small well circumscribed, slow growing, painful, rubbery or
semi-firm, lobulated mass, firmly adherent to the surrounding
Fascicular growth pattern (bundles intersect at right angles).
Palisading of spindle cells with eosinophilic fibrillary cytoplasm,
Nuclei are cigar-shaped and blunt-ended with variable atypia,
often with cytoplasmic vacuoles at both ends of nuclei (unlike
Mitotic figures are common. (5 > 10 HPF)
Ischemic areas showing stromal fibrosis and hyalinisation.
•May have hemangiopericytoma-
like vasculature, nuclear
palisading, myxoid change.
•Often infiltrates into adjacent
Massons trichrome showing longitudinal
striations. ( red hair like streaks in
Benign neoplasm of striated muscle with varying degree of
differentiation and maturity.
Well circumscribed/ encapsulated.
TYPES OF RHABDOMYOMA
Fetal (Spindle cells)
32. 70% occurs in men (5:1 ratio)
Oral cavity- palate, floor of the mouth, tongue
Appears as a nodular mass and grows to many centimeters.
Fetal variant: young children with male predilection
Face, periauricular region, nasopharynx.
34. Less mature, pleomorphic, polygonal muscle cells with spindle shaped
More cellular, with myxoid stroma.
Myxoid/ Classic, Intermediate/ Cellular/ Juvenile Fetal
Undifferentiated round mesenchymal cells and
immature skeletal muscle cells within myxoid or
The bipolar, immature skeletal muscle cells
have tapered eosinophilic cytoplasmic
processes and closely resemble the
myotubular stage of striated muscle
development, and the undifferentiated cells
have minimal cytoplasm and round or oval
Mucosal tumors have a pseudo
cambium layer of plasma cells and
lymphocytes resembling embryonal
rhabdomyosarcoma, but there is no
atypia and no mitotic figures
•Infantile fibromatosis: deep location, fascicles of spindle cells, no
cross striations, no undifferentiated cells
•Spindle cell variant of embryonal rhabdomyosarcoma: resembles
cellular variant of fetal rhabdomyoma but has cellular pleomorphism
and tumor cell necrosis
37. SPINDLE CELL RHABDOMYOSARCOMA
(VARIANT OF EMBRYONAL
Rhabdomyosarcoma (RMS) originates from immature cells that
are destined to differentiate into striated skeletal muscle
More common in young children; 60% soft tissue sarcoma in
Embryonal type most common in first 10 yrs of life (60%) -
spindle cell variant and botryoid variant
39. CLINICAL FEATURES
It presents as a rapidly growing soft tissue mass.
The clinical symptoms produced are based on their location.
Chiefly from orbital, facial and cervical musculature.
The head and neck lesions can cause proptosis, diplopia,
sinusitis, or unilateral deafness, depending on their location
43. DIFFERENTIAL DIAGNOSIS
Fibrosarcoma: herringbone pattern, may have similar morphology
but no rhabdomyoblasts, negative for skeletal muscle markers
Infantile fibromatosis: deep location, fascicles of spindle cells, no
cross striations, no undifferentiated cells
Leiomyosarcoma: usually high grade, cigar shaped nuclei, mitotic
figures and necrosis, no rhabdomyoblasts, often positive for
caldesmon, negative for myoglobin
Rhabdomyoma: benign tumor of skeletal muscle differentiation, no
rhabdomyoblasts, no pleomorphism, no necrosis
49. TRAUMATIC NEUROMA
Exuberant attempt at repair of damaged nerve trunk
Small nodule or swelling of mucosa, typically near mental
foramen, slow growing, rarely reaches to greater size
Pressure causes pain
56. NEURILEMMOMA (Neurinoma/
Lemmoma/ Perineural fibroblastoma)
Benign neoplasm that is derived from proliferation of
schwann cells of the neurilemma or nerve sheath
Slow growing, encapsulated tumor
Tongue common site
Intraosseous lesion – Mandible.
Biphasic: compact hypercellular Antoni A areas and myxoid
hypocellular Antoni B areas (may be absent in small tumors)
Cells are narrow, elongate, wavy with tapered ends interspersed
with collagen fibres.
Nuclear palisading around fibrillary process (Verocay bodies)
are often seen in cellular areas
Large irregularly spaced vessels are most prominent in Antoni
Occurs even without neurofibromatosis, tumors usually have
epithelioid features and often areas of benign schwannoma.
Transforms to MPNST, angiosarcoma or epithelioid malignant
Most common sites are limb, limb girdles, head / neck
Schwannoma with MPNST: benign schwannoma with no other
primary tumor that may have metastasized to schwannoma,
histologically malignant cells resembling epithelioid MPNST; 5 year
survival < 20%
Most common type of peripheral nerve neoplasm
Arises from- schwann cells, perineural fibroblasts.
Appears as slow growing, soft painless lesion of varying size
Three growth pattern observed: localised, diffuse or plexiform
Palate, buccal mucosa and alveolar ridge
Mandibular nerve is involved (intraosseous)
Proliferation of all elements of peripheral nerves
Schwann cells with wire like collagen fibrils (wavy serpentine
nuclei, pointed ends), stromal mucosubstances, mast cells, Wagner-
Meissner corpuscles, Pacinian corpuscles, axons (highlight with silver
or acetylcholinesterase stain, NSE, neurofilament), fibroblasts and
Perineurial cells in plexiform types, mitotic figures are rare
May be infiltrative, have myxoid areas, contain melanin pigment,
have epitheloid morphology
No Verocay bodies, no nuclear palisading
No hyalinized thickening of vessel walls.
70. The cells are associated intimately with
wire like strands of collagen that is
correlated to “shredded carrots”.
Strongly S-100 protein positive.
Conventional and plexiform neurofibromas may also contain
variable numbers of EMA-positive perineurial cells and
Toluidine blue for mast cell (histochemical staining)
74. PALISADED ENCAPSULATED
SOLITARY CIRCUMSCRIBED NEUROMA
Generally considered reactive than a neoplasm
Striking predilection for face
Nose and cheek common areas
Oral cavity - hard palate and maxilla
5-7th decade of life, no gender predilection
Smooth surface, painless, dome shaped nodule <1cm.
79. IMMUNOHISTOCHEMISTRY OF PEN
Silver stains for axons and luxol fast blue stain for myelin
will confirm the presence of Neural tissue within the tumor
IHC : S-100 positive
80. MALIGNANT PERIPHERAL NERVE
Malignant schwannoma, Malignant neurilemmoma,
Neurogenic sarcoma, Neurofibrosarcoma
Malignant tumor arising from or differentiating toward cells of
the peripheral nerve sheath.
Spindle cell malignancy of peripheral nerve schwann cells.
It is found in at least 4% of patients with neurofibromatosis I.
Mostly 20-50 years
Neck, tongue, soft palate.
Central- mandible more common
The tumor is an enlarging mass that sometimes exhibits rapid
Paresthesia, muscle atrophy, and weakness may be present,
depending on whether a major nerve trunk is involved.
Recur locally, distant metastases frequent
82. CRITERIA that must be satisfied before a diagnosis is made is that
the tumor is histologically malignant and is identified arising :
1. from a peripheral nerve
2. from a neurofibroma schwannoma, ganglioneuroma,
ganglioneuroblastoma or pheochromocytoma
3. in a patient with NF-I and exhibiting the same histologic feature as
MPNSTs found originating from a peripheral nerve
4. in a patient without NF-1 but having the same histologic features as
well as demonstrating immunoreactivity for S-100 protein. In 50-
70% of cases, S-100 protein reactivity is found in scattered tumor
83. Monomorphic serpentine cells (nuclear contour of schwann cells).
Frequent mitotic figures, cellular and nuclear pleomorphism.
Spindle cells in sweeping fascicles with hypocellular & myxoid areas.
May have glandular differentiation (positive for keratin, EMA, CEA,
chromogranin); if so, presume malignant
Note: some have no discernable Schwannian features at any level
HISTOPATHOLOGY OF MPNST
Also known as “Rouget cells” (Charles Rouget)
Zimmerman termed it as pericytes
Present around small blood vessels, wrapped around the basal
surface of the endothelium
90. ORIGIN OF PERICYTES
It has recently been shown that perivascular cells (i.e, pericytes or smooth
muscle cells) and endothelial cells can be derived from a common
Incubation of these progenitor cells with PDGF-BB stimulates their
differentiation into pericytes/smooth muscle cells,
Whereas VEGF stimulates their differentiation into endothelial cells.
It has been suggested that pericyte may also be derived from smooth
muscle cells, fibroblasts, endothelial cells, and the bone marrow
Being derived from multiple cell types, it is now apparent that pericytes
have multilineage potential and are capable of differentiating into a
variety of different cell type.
92. SPINDLE CELL HEMANGIOMA
In 1986, Weiss and Enzinger described a unique vascular tumor with
combined features of both cavernous hemangioma and Kaposi
The spindle cell hemangioendothelioma was considered to be an
intermediate or low-grade malignancy, with a biologic behavior
between a hemangioma and an angiosarcoma.
It affects almost exclusively the dermis and subcutis of the distal
Spindle cell hemangioma presents as a solitary tumor or as multiple
nodules clustered within the same region.
Multifocal SCHs have been
associated with Maffucci
Von Willenbrand disease,
leukemia, early-onset varicose
veins, and epithelioid
Composed of thin walled cavernous
vessels lined by flat endothelial cells and
contain mixture of erythrocytes and
Between cavernous spaces are bland spindle
areas are seen resembling kaposis sarcoma.
Bland spindle cell proliferations between vascular lumina with extravasated
erythrocytes (similar to Kaposi's sarcoma), but also with vacuolated cells and
epithelioid endothelial cells (unlike Kaposi's sarcoma)
99. DIFFERENTIAL DIAGNOSIS
Kaposi’s Sarcoma- rarely contains cavernous vessels with thrombi
and phleboliths and lacks epithelioid cells, and the spindle cells
react for the endothelial marker CD34.
On the other hand, SCH does not present the hyaline globules seen
in Kaposi sarcoma, and does not express human herpes virus 8
latent nuclear antigen.
Spindle cells are negative for endothelial markers
and react for vimentin, and occasionally for actin, desmin, factor
XIIIa, lysozyme, alpha-1-antithrypsine, and HAM-56 antigen.
100. KAPOSI’S SARCOMA
Multicentric proliferation of vascular and spindle cell
components- Moritz Kaposi (1872)
Predominantly associated with HIV infection
Four major clinical presentation: classic, endemic (African),
immunosuppression associated (transplant), AIDS related
Classic (Mediterranean) Kaposi sarcoma (KS)
M > F, 40 - 70 years, Mediterranean or Ashkenazi origin
Usually lower extremities
Soft bluish nodules of palate, gingiva.
Endemic (African) KS
Adults and children in equatorial Africa
Lymphadenopathic form is aggressive
AIDS associated (epidemic) KS
Disseminated mucocutaneous / visceral lesions-Aggressive
Palatal and gingival mucosa.
Immmunosuppression asso: KS
(autoimmune disease, drugs, post-transplant)
CMI – lost in host
Signs of a subtle vasoformative process composed of newly formed slit-like
or somewhat jagged vascular spaces.
The protrusion of native microscopic vascular structures into the lumens of
more ectatic neoplastic channels results in the characteristic promontory sign.
104. Plaque stage
More diffuse vascular infiltrate, accompanied by greater cellularity.
The lesional cells tend to be more spindled and arranged in short, sometimes
haphazard fascicles. Fascicles cut in cross section demonstrate a sieve-like app:
Intra- and extracellular hyaline globules.
The arrows indicate so-called "autolumination", with paranuclear vacuoles
105. Nodular stage
• The dermis is expanded by a solid tumor nodule.
• Fascicles of relatively monomorphic spindled cells, with slit-like vascular
channels containing erythrocytes.
112. PROGNOSTIC FACTORS
Disseminated KS is often fatal
AIDS related and African KS are more aggressive than Mediterranean KS
Iatrogenic KS may regress when immunosuppression is discontinued
Mainly palliative, based on extent of disease:
External beam radiation, laser therapy, cryotherapy, photodynamic therapy
Topical alitretoin gel, topical immunotherapy (imiquimod), intralesional
chemotherapy (vinblastine), surgical excision
IV chemo / immunotherapy (e.g. liposomal anthracyclines and taxanes),
interferon alpha, HAART if HIV+
Tumor entirely composed of myoepithelial cells
Accounts for less than 1% of salivary gland tumor
Parotid common, followed by palate, lip and cheek
Between 30-50yrs age
Equal gender distribution
Asymptomatic slow growing mass
121. MYOEPITHELIAL CARCINOMA
Defined as malignant epithelial neoplasm whose tumor
cells demonstrate cytologic differentiation toward
myoepithelial cells and lacks ductal or acinar differentiation
Painless mass, common in parotid,
Maxillary gingiva and alveolar mucosa
Equal sex predilection, adult age
122. HISTOPATHOLOGY OF
Similar to myoepithelioma
Quite cellular, more suggestive of
sarcoma than carcinoma
Some part of stroma shows myxoid
CK, S100, SMA, GFAP (glial
fibrillary acidic protein)
123. SYNOVIAL SARCOMA
Synovial sarcoma is a morphologically, clinically and
genetically distinct entity that may occur at any site
3rd and 5th decades of life
Male female ratio 3:2
common site of involvement is the lower extremity
Oral lesions occur in the tongue, soft palate, cheek and parotid
Deep seated, slow growing, palpable mass that may or may
not be associated with pain
125. CELLULAR ELEMENTS AND THE DEGREE
Biphasic (epithelioid and spindle cell)
Monophasic spindle cell
Monophasic epithelioid type
Poorly differentiated (round cell) type - Enzinger
126. GROSS APPEARANCE OF SYNOVIAL
Pink well demarcated fleshy mass with solid/hemorraghic
areas and cystic components with areas of calcification.
Increase in calcification is associated with good prognosis.
Biphasic have spindle cells and plump epithelial cells forming glands /
Monophasic lack the epithelial cells
Spindle cells are arranged in plump fascicles with hyalinization and
distinct lobulation accompanied by mast cells, occasional osseous or
cartilaginous metaplasia, focal whorling
May have hemangiopericytomatous vascular pattern
129. MONOPHASIC FIBROUS SYNOVIAL
Typically, there are densely cellular
sheets or vague fascicles, with
occasional nuclear palisading.
Many tumours display, at least focally,
a prominent haemangiopericytomatous
vascular pattern.. Myxoid change is
usually focal and rarely diffuse and
predominant, with alternating hypocellular
and more cellular areas, and microcyst
formation. Mast cells can be abundant.
Osteosarcoma is a malignancy of mesenchymal cells able to
produce osteoid or immature bone.
It is uncommon and represents 6-8% of all osteosarcomas.
It occurs most often in the third and fourth decades of life.
Approximately 25% of osteosarcomas consist predominantly of spindle tumor
cells and can be classified as fibroblastic osteosarcoma. Osteoid production is
minimal and seen focally; although in this case, osteoid matrix was readily found.
Fibroblastic osteosarcomas are highly vascular and may resemble
1. Storiform pattern of arrangement of fibroblasts with atypical; spindle cells.
2. Osteoclasts like giant cells closely associated with tumour osteoid.
3. markedly cellular lesion with proliferating fibroblasts.
4. Presence of few reactionary giant cells.
137. GRADING AND STAGING OF
American joint committee on cancer (AJCC) and
musculoskeletal tumor society developed a staging system
Size of primary tumors(T)
Involvement of lymph node (N)
Presence of metastasis (M)
Type and grade of sarcoma (G)
In 1997 other features were added
138. 2010 AJCC staging of soft tissue malignancy (7th edition)
Tx Primary tumor cannot be assessed
T0 No evidence of primary tumor
T1 Tumor size 5cmm or less in dimension
T1a Superficial tumor
T1b Deep tumor
T2 Tmor more than 5cmm in dimension
T2a Superficial tumor
T2b Deep tumor
Nx Regional lymphnode cannot be assessed
N0 No regional lymphnode involved
N1 Metastasis to regional lymphnode
M0 No distant metastasis
M1 Distant metastasis
Gx Grade cannot be assessed
G1 Grade 1
G2 Grade 2
G3 Grade 3
Spindle cell lesions of head & neck are diverse & diagnostically
Clinical correlation is valuable.
Pathologists should take particular care before rendering final
Rule of thumb –in adults; malignant spindle cell are more likely to
represent carcinoma or melanoma than a true sarcoma.
Enzinger and weiss; Soft tissue tumors. fifth edition
Brad . W . Neville, Douglas D . Damm , Carl M . Allen. Oral and
maxillofacial pathology. 2nd edition 2004
SHAFER, Text book of oral pathology. 6th edition 2006
Regezi, Sciubba, Jordon. Oral Pathology.
Douglas .R. Gnepp; Diagnostic surgical pathology of head and neck;
Cawson’s essentials of Oral pathology. 7th edition.
Contemporary oral & maxillofacial pathology. 2nd edition. J Philip
Textbook of oral pathology. Sanjay Saraf.
smooth muscle cells arise from undifferentiated mesenchymal cells. These cells differentiate first into mitotically active cells, myoblasts, which contain a few myofilaments. Myoblasts give rise to the cells which will differentiate into mature smooth muscle cells.
Activation of key regulatory proteins by growth factors, cytokines or matrix components leads to commitment of stem cells to differentiate into specific cellular lineages
They appear spindle or fusiform in shape having a broad central part and tapering ends. Nucleus is cylinder and placed centrally. The length of smooth muscle fibers are highly variable and they usually aggregate to form bundles or fasicles. These fasicles or bundles are surrounded by a network of delicate fibers of collagen, reticulin and elastic fibers that holds the myocytes together.
The sarcoplasm contains mitochondria, golgi complex, some endoplasmic reticulum, glycogen and free ribosomes. These organelles and inclusions are largely confined to the perinuclear cytoplasm located at the poles of the nucleus. The sarcoplasmic reticulum is more poorly developed, consisting of narrow sarcotubules with no terminal cisternae. The remainder of the cytoplasm is filled with myofilaments oriented parallel to the long axis of the cell.
Myofilaments are composed of actin and myosin. The thin filaments contain actin with tropomyosin. No troponin is present in the smooth muscle cells. Thick filaments project the heavy meromyosin heads all along their length. Thus, there is a larger surface area for the interaction of myosin with actin. Focal densities seen in the cytoplasm or at the cell membrane are organizational sites for the thick and thin filaments (actin and myosin) to interact and to be
held in position. Desmin or vimentin filaments also bind at these sites to help hold the filaments together. These intermediate filaments help relay the contraction and help to shorten the cell. The dense bodies also contain alpha actinin, an actin binding protein. These dense bodies are similar to the Z lines of the striated muscle
Each myofiber is a multinucleate syncytium formed by fusion of precursor skeletal muscle cells termed myoblasts
skeletal muscle in cross-section shows parts of five fascicles of muscle. Each fascicle is surrounded by thin, delicate perimysium. The myofibers are of relatively uniform size and shape and fit together in a mosaic pattern. The fibers, which appear to be in almost direct contact with one another, are separated by thin, almost invisible endomysium. In contrast, in cases in which fibrosis is present, the muscle fibers appear separated. The myofiber nuclei are normally located at the periphery of the cells, and the cytoplasm is fairly uniformly distributed. At high power (see the following image), the endomysium separating the myofibers can be observed as normally so thin and delicate it is almost invisible, and the contiguous myofibers appear to have almost no space between them. The sarcoplasm appears relatively uniform throughout the cell.
Composed of fascicles of interlacing spindle shaped cells with adundant eosinophilic cytoplasm and moderately large centrally loacted cigar shaped or blunt end nuclei, often with mild atypia. Cellularity vary depending upoon tumor differentiation. Well differentiated shows more spindle cells in streaming or interweaving fascicles
Myxoid type: primitive oval or spindle cells with indisctinct cytoplasm, interspersed immature skeletal muscle fibers reminiscent of fetal myotubles seen during seven week of interauterine life, richly myxoid.
Intermediate type: presence of numerous differentiated muscle fibers, less conspicous or absent spindle shaped mesenchymal cells and little or no myxoid stroma.
Adult rabdomyoma: The predominant cells are broad, strap shaped muscle cells with abundant eosinophilic cytoplasm, centrally located vesicular nuclei and frequent cross striations are seen
Embryonla is spindle cell type
Its chiefly composed of spindle cells, arranged hapazardly, the nuclei are ovoid or elongated packd with chromatin. Even in storiform pttern the cells can be arranged mimicing leiomyosarcoma. Bizarre large cells are seen called racket cells, strap cells and ribbon cells showing streaming of cytoplasmic process. . Unlike embryonal rabdomyosarcoma, tadpole cells, racket shaped cells and cells with cross straition are not seen.
In H& E stained section the lipid in the myelin surrounding individual nerve fiber dissolves during dehydration and clearing agents. Hence in TS the nerve fibers perviously occupied by myelin sheath will leave little round space with central axon surrounded by pale staind schwann cells cytoplasm is seen on the outer surface of the myelin space.
In LS they appear wavy and is accentuated by waviness of the nuclei of the schwann cells
Repair of damaged nerve begins with proliferation of the axis cylinders, the cells of the neural sheaths and the endoneurium. Reinnervation generally occurs until the proliferating proximal end meets some obstruction and results in unorganised bulbous or nodular mass of nerve fibers.
Irregular mass and often interlacing neurofibrils. The proliferation of nerve fibres occurs in small discrete bundles or spread diffusely throughout the tissue.
Luxol fast blue stain will show some fibers to be myelinated while others are not
NF1 ad NF2
Histology varies depending on content of cells, stromal mucin and collagen. Characterized by interlacing bundles of elongated cells with wavy and darkly stained nuclei. The cells are associated intimately with wire like strands of collagen that is correlated to “shredded carrots”. Small to moderate amounts of mucoid material separate the cells and collagen fibers. Mast cells are seen dispersed. . Sometime the lesion is highly cellular and consists of schwann cells and will be devoid of mucoid material. In this case the cells are arranged in fasicles, storiform or whorl pattern.. Areas of antoni A pattern can be demonstrated like schwannoma. More myxoid area mimics myxoma.
Well circumscribed, nodule occupy deep dermis and subcutaneous tissue, consists of solid proliferation of schwann cells and lack variety of stromal changes like mucodi, myxoid changes some places they resemble schwannoma showing palisaded arrangement of cells
Resemble fibrosarcoma. Unlike fibrosarcoma they are markedly irregular arrangement of cells the celly show spindle wavy coma shap. Cytoplasm is lightly stained and is indistict. Cells are arranged in sweping fascicles but there is greater variation in organisation. Zone of hypocellularity and myxoid areas are evident. Cellular pleomorphism is noted.
The periendothelial location of pericytes is frequently confused with the periendothelial location of vascular smooth muscle cells (vSMCs), fibroblasts, macrophages, and even epithelial cells. Although the field has generally adopted the view that pericytes belong to the same lineage and category of cells as vSMCs, it should be remembered that there is no single molecular marker known that can be used to unequivocally identify pericytes and distinguish them from vSMCs or other mesenchymal cells. The multiple markers that are commonly applied are neither specific nor stable in their expression.As a result, the term pericyte is frequently used in the literature to denote any microvascular periendothelial mesenchymal cell.
Slender elongated pale stained spindle cells or stellate shaped cells present around the capillaries and venules. They are embedded in the basement membrane adjacent to the endothelial cell junctions. They have multiple elongated processes that wrap around the vessels
There is no single molecular marker to be used unequivocally to identify pericytes due to its multilineage origin
Each pericyte possesses a cell body with a prominent nucleus and a small amount of surrounding cytoplasm. Cytoplasm contains large numbers of plasmalemmal vesicles, contractile microfilament bundles, and glycogen deposits. Protruding from the cell body are long processes which parallel the long axis of the capillaries and taper to smaller processes which encircle the capillary wall. Pericytes are embedded within the basement membrane which surrounds the capillary tubes. In vitro, evidence suggests that both endothelial cells (EC) and pericytes contribute to the formation of the basement membrane. Their processes penetrate the basement membrane to directly contact the underlying endothelium and, in a reciprocal manner, endothelial processes penetrate into the pericytes.
Histologically composed of thin walled cavernous vessels lined by flat endothelial cells and contain mixture of erythrocytes and thrombi. Between cavernous spaces are bland spindle areas are seen resembling kaposis sarcoma. Unlike kaposis sarcoma which contain distinct round or epitheloid cells containing cytoplasmic .vacuoles. In extreme cases these vacuoles can be confused with entrapped fat cells/ fat
Tumor derived from pericytes. Consists of numerous vascular channels with plump endothelial cells, surrounded by tightly packed proliferation of oval and spindle shaped cells with hyperchromtic nuclei and moderate amount of cytoplasm. The branching vascular channel appear like staghorn pattern
Patch stage: this is diagnostic cahllenge to diagnose at this stage. , there are signs of a subtle vasoformative process composed of newly formed slit-like or somewhat jagged vascular spaces, which tend to be more conspicuous in the immediate vicinity of native dermal vessels and cutaneous appendages [1, 2, 3, 4]. The protrusion of these native microscopic vascular structures into the lumens of more ectatic neoplastic channels results in the characteristic promontory sign (Figure 1). The intervening dermis frequently reveals dissection of its collagen bundles by slit-like vascular spaces lined by a monolayer of relatively banal, flattened endothelial cells, with a variable degree of erythrocyte extravasation. The newly formed channels often contain red blood cells. There is also a noticeable mild background inflammatory cell infiltrate comprising lymphocytes and plasma cells, often accompanied by a contingent of hemosiderin-laden macropahges.
Plaque type: more diffuse dermal vascular infiltrate, accompanied by greater cellularity and occasional extension of this process into the underlying subcutaneous adipose tissue. The lesional cells tend to be more spindled and arranged in short, sometimes haphazard fascicles [1, 2, 3, 4]. Fascicles cut in cross section demonstrate a sieve-like appearance. Mitotic figures are sparse and there is no significant nuclear or cytological pleomorphism. Intra- and extracellular hyaline globules, probably representing effete erythrocytes, are often seen. Large numbers of intracellular and extracellular eosinophilic hyaline globules are visible in this field (H&E stain). The arrows indicate so-called "autolumination", with paranuclear vacuoles containing erythrocytes.
Nodular type: The dermis is expanded by a solid tumor nodule (H&E stain). B. Fascicles of relatively monomorphic spindled cells, with slit-like vascular channels containing erythrocytes (H&E stain)
Other then salivary glands these are present in mammary glands, lacrimal glands and sweat glands
Myoepithelial cells appear structurally similar irrespective of the organ or species. They are formed around the secretory end pieces,, have spider like or stellate shape with flattened nucleus, scanty perinuclear cytoplasm and long branching processes. In intercalated duct the cells are more fusiform and are elongated with few short processes and oriented length wise along the duct
ULTRASTRUCTURE:The ultrastructural features are similar to those of smooth muscle cell. The processes are
filled with filaments of actin and soluble myosin. The fine filaments are about 6nm (60Ǻ) thick
Small dense bodies are frequently present between the thin filaments, which form a
cytoskeletal network in association with 10nm (100Ǻ) diameter filaments. The cell membrane
has numerous caveolae, which presumably function in initiating the contraction. Most of the
other cell organelles are located in the perinuclear cytoplasm.
Gross appreance: well encapsulated solid mass, lacks myxoid or chondroid features unlike pleomorphic aedenoma
Microscopically consists of spindle shaped cells with eosinophilic cytoplasm. Tend to be more cellular. Arranged in difuse sheets or intelacing fasicles. Epitheloid or clear cells and plasmacytoid cells may be present. Tumor is difficult to measure at ight microscopic level.
Lack of muscle specific actin suggests the possibility that at least in some
myoepitheliomas, the tumor cells are differentiated more like certain basal cells, ((which lack
muscle-specific actin,)) of the striated and excretory ducts of normal salivary glands.17
Only 4 cases documented by ellis
Bursae: a fluid-filled sac or sac-like cavity, especially one countering friction at a joint.
These cells originate from mesenchymal cells
It varies in structure. It is dependent on local and mechanical factors and nature of the underlying tissue. When the joint is subjected to high pressure the membrane appears flat and acellular, weheras whn the joint is under less stress they have a redundant surface lined by cells that resemble cuboidal or columar epithelium. They are seperated from each other by a small amount of connective tissue ground substance. No basement membrane is present beneath these lining cells and underlying capilalries, therefore they have no barrier seperating them from the joint cavity.
The spindle cell component often occurs alone as monophasic synovial sarcoma. Typically, there are densely cellular sheets or vague fascicles, with occasional nuclear palisading. Many tumours display, at least focally, a
prominent haemangiopericytomatous vascular pattern. Stromal collagen is usually wiry
and scanty but some tumours have foci of hyalinization. Myxoid change is usually focal and
rarely diffuse and predominant, with alternating hypocellular and more cellular areas, and
microcyst formation. Mast cells can be abundant.
High grade malignant bone tumor, long bones more common. Occur in the age group of 5yrs to 50yrs. Male predominance.
Histologically three types: osteoblastic, chondroblastic and fibroblastic
Simple type and WHO type-
Simple type: resembles relatively a dental follicle, fibers quite delicate and there is considerable amount of ground substances resemblinf fibromyxom. Exhibits few inactive odontogenic epithelial island.
WHO type: cellular connnective tissue, foci f calcified collagenous component resembling dysplastic cementum or osteoid or atubular dentin. Islands or strands of inactive odontogenic epithelial island.
Superficial is exclusively beneath superficial fascia without invasion of the fascia, deep is exclusively the superficail fascia, invasion through the fascia.
Histological grading is based on cellularity, cellular pleomorphism, mitotic activity, amount of stroma, infiltrative or expansive growth and necrosis.