Benign Tumors and Tumor like Lesions

Slide 1 · Benign Tumors and Tumor-like Lesions

Pediatric pathology: conceptual classification, morphology and clinical relevance

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning outcomes

Distinguish true benign tumors, hamartomas and heterotopias using tissue identity and architecture.

Differentiate pediatric vascular tumors from vascular malformations and recognize their clinical behavior.

Relate fibrous lesions and teratomas to morphology, molecular findings and risk.

Classification → morphology → biological behavior → clinical consequence

Slide 3 · Why the pediatric context matters

Tumor-like developmental masses are especially important mimics of neoplasia in infants and children.

Benign pediatric tumors outnumber childhood malignant tumors in the chapter’s overview.

Benign morphology does not exclude major clinical problems caused by size or location.

Slide 4 · Two different questions about a mass

What is the lesion?

→

Is it truly neoplastic?

→

What harm can it cause?

Identity, clonality and architecture address classification.

Site, size and functional effects address clinical risk.

Slide 5 · Pediatric versus adult tumor patterns

Pediatric context

Adult context

Common childhood solid neoplasms emphasize mesenchymal soft tissue origin.

The chapter contrasts this with frequent epithelial tumors in adults.

Developmental tumor-like lesions are an important diagnostic problem.

This pediatric developmental context is less prominent in the overview of adult tumors.

Behavior often requires age- and entity-specific interpretation.

Adult morphologic analogies may mislead for some pediatric tumors.

The comparison is qualitative; No frequency estimate is implied.

Slide 6 · Three groups warrant particular attention

Vascular lesions

Proliferative vascular tumors and nonproliferative vascular malformations.

Fibrous lesions

Fibroblastic or myofibroblastic proliferations with variable cellularity and behavior.

Teratomas

Germ-cell tumors where tissue maturity contributes to risk assessment.

These are the three groups singled out by Robbins in the overview.

Slide 7 · A lesion can be benign yet clinically serious

Mass effect can disrupt organ function despite bland histology.

Exposed sites may cause a prominent cosmetic or structural concern.

The lesion’s trajectory—growth, stability or involution—changes clinical interpretation.

Severity depends on behavior and anatomy, not only malignant potential.

Slide 8 · Reasoning from morphology to consequences

Tissue identity

→

Growth architecture

→

Anatomical location

→

Clinical effect

A familiar tissue type may still be abnormal in its position.

Consider functional compromise even when malignant features are absent.

Slide 9 · Developmental mimics and true neoplasms

Heterotopia

Normal differentiated tissue located outside its usual anatomical site.

Hamartoma

Focal overgrowth of the tissue elements native to an organ, in disordered arrangement.

Neoplasm

An autonomous proliferative lesion; May be benign or malignant.

The boundary between hamartoma and benign neoplasm is not always absolute.

Slide 10 · Diagnostic questions for a childhood mass

Are the cells native to this organ or located ectopically?

Is the microscopic tissue arrangement preserved or disordered?

Does the lesion proliferate, remain stable or regress?

Could an important structure be compromised by the mass?

Slide 11 · Heterotopia: Tissue in the wrong location

Differentiated tissue in the wrong site

Differentiated, microscopically normal tissue appears at an abnormal site.

The term choristoma is a synonym.

The primary abnormality is location, not necessarily cytologic atypia.

Slide 12 · Heterotopia is not defined by malignancy

Property

Interpretation

Tissue differentiation

Microscopically normal or mature tissue.

Anatomical position

Outside the site where that tissue normally resides.

Clinical mimic

A focal rest or mass may resemble a neoplasm clinically.

Usual significance

Generally minor, although rare neoplasms can arise in rests.

Slide 13 · Pancreatic heterotopia: A concrete example

A pancreatic tissue rest can be present in the gastric wall.

The same heterotopic tissue can occur in the wall of the small intestine.

Identification depends on tissue type plus the unexpected anatomical site.

An ectopic rest can be mistaken for a mass arising from the host organ.

Slide 14 · How heterotopia becomes a diagnostic mimic

Normal differentiated tissue

→

Unexpected organ location

→

Mass-like presentation

→

Neoplastic concern

Appearance as a discrete lesion does not prove true neoplasia.

Histology can clarify tissue identity and relationship to the host site.

Slide 15 · Adrenal rests: Examples of ectopic location

Adrenal cortical cells may be present within the kidney.

Adrenal rests are also described in the lung and ovary.

These rests should be recognized as ectopic adrenal tissue, not automatically as a primary tumor of the host organ.

Slide 16 · Interpret an ectopic adrenal rest

Illustrative scenario: Mature adrenal-type tissue is detected within an ovarian lesion.

Question

What classification should first be considered?

Reasoned interpretation

A heterotopic adrenal rest: The tissue identity is preserved but its location is ectopic.

If an actual neoplasm arises there, reclassify the new proliferation on its merits.

Slide 17 · Rare neoplasia arising in heterotopic rests

Most ectopic rests have little clinical significance.

A genuine neoplasm can occasionally originate within the heterotopic tissue.

The possibility with adrenal cortical carcinoma arising in the ovary.

Rare transformation does not make all ectopic rests premalignant.

Slide 18 · Heterotopia versus a primary host-organ mass

Observation

Why it matters

Mature cells matching another organ

Supports a heterotopic rest when found ectopically.

Mass in stomach or bowel wall

A pancreatic rest is among the possible explanations.

Mass in ovary with adrenal-type tissue

Consider ectopic adrenal tissue.

Evidence of a new neoplastic proliferation

A rare secondary neoplasm may arise within an ectopic rest.

Slide 19 · Hamartoma: Native tissues, abnormal arrangement

Native elements; Disorganized focal architecture

A hamartoma is a focal excessive growth of elements native to the involved organ.

The component cells are mature and resemble those elsewhere in that organ.

Their spatial organization differs from the normal surrounding tissue.

Slide 20 · Architecture separates two developmental patterns

Heterotopia

Hamartoma

A normal tissue type appears in a location where it does not belong.

Elements are native to the organ where the mass occurs.

Anatomical location is the defining abnormality.

Excess and disorganization of native elements are central.

Example: pancreatic tissue within gastric wall.

Examples may include selected vascular, cardiac or cystic lesions.

Slide 21 · Why architecture matters in hamartomas

Mature cells alone do not imply a normally formed organ structure.

A benign collection can distort the normal spatial relationships of tissue components.

The diagnosis requires considering both cellular identity and architecture.

Slide 22 · Normal architecture as a hamartoma comparator

Organized tissue in the normal location

Outside the lesion, native tissue shows an expected architectural pattern.

The focus contains similar differentiated tissue components.

Local overgrowth produces a disordered, mass-forming arrangement.

Slide 23 · Hamartoma and neoplasm are not mutually exclusive labels

The demarcation between a hamartoma and a benign tumor can be indistinct.

Both categories may display clonality.

Clonal growth alone should not be used to redefine every hamartoma as a malignant lesion.

Classification requires integrating developmental and proliferative features.

Slide 24 · Examples with debated classification

Vascular

Hemangiomas and lymphangiomas may be interpreted differently by authors.

Solid organ

Cardiac rhabdomyoma and hepatic adenoma are among lesions discussed in this context.

Developmental cysts

Cysts in kidney, lung and pancreas may be interpreted as hamartomatous in some settings.

These are examples of classification ambiguity, not universal categorical diagnoses.

Slide 25 · Cardiac rhabdomyoma as a classification example

Rhabdomyoma of the heart among lesions interpreted variably as hamartoma or true neoplasm.

The defining teaching problem is classification, not a claim that every cardiac rhabdomyoma is a hamartoma.

The organ-specific lesion requires its own focused pathology assessment.

Slide 26 · Lymphangioma and vascular lesion terminology

A lymphangioma may be described as a hamartomatous lesion in some classifications.

Vascular tumor and vascular malformation terminology also overlaps clinically.

Avoid applying a universal label before establishing the relevant lesion subtype.

Terminologic uncertainty is explicitly acknowledged by Robbins.

Slide 27 · Developmental cysts and the hamartoma spectrum

Developmental cysts in kidney, lung and pancreas are included as possible hamartomatous processes.

Their organ-native elements distinguish them conceptually from heterotopic rests.

An organ-specific differential diagnosis remains necessary; The broad label is insufficient.

Slide 28 · Hamartoma reasoning exercise

Illustrative scenario: A well-differentiated focal mass contains tissues native to the organ, but their architecture is disorganized.

Question

Which descriptive category fits these features?

Reasoned interpretation

Hamartoma is a reasonable descriptive classification. Its distinction from benign neoplasm may remain blurred.

An apparently benign lesion can still cause clinical problems through size or site.

Slide 29 · Why benign histology does not settle management

Mature benign cells

→

Mass size and growth

→

Anatomical constraints

→

Functional risk

Risk and morphology provide different pieces of information.

Robbins specifically cautions that benign lesions may rarely be life-threatening.

Slide 30 · Framework for pediatric vascular masses

Proliferative tumor

Mass-forming vascular lesion with a proliferative component.

Vascular malformation

A structurally abnormal vascular lesion classified as nonproliferative.

Terminology challenge

Clinical labels may not consistently reflect this biological distinction.

Do not equate every flat red-blue skin lesion with a proliferative hemangioma.

Slide 31 · Vascular tumors versus vascular malformations

Feature

Vascular tumor

Vascular malformation

Concept

Proliferative vascular lesion.

Nonproliferative vascular anomaly.

Hemangioma label

Strictly refers to benign vascular tumors.

Sometimes applied imprecisely to malformations.

Clinical differentiation

Can be difficult by appearance alone.

Can be difficult by morphology alone.

Teaching emphasis

Consider lesion growth pattern.

Consider abnormal vessel architecture.

Slide 32 · What a vascular lesion diagram can—and cannot—show

Schematic vascular channels; Not a micrograph

Vascular lesions comprise mass-forming abnormalities of vessels.

The diagram illustrates channels only; It does not establish a diagnosis.

Clinical evolution and formal classification are needed beyond the vessel outline.

Slide 33 · The hemangioma naming pitfall

In strict usage, hemangioma denotes a benign vascular neoplasm.

In less precise usage, the same word is applied to certain vascular malformations.

Document the intended biological category instead of relying solely on the label.

A naming error can obscure proliferative versus nonproliferative biology.

Slide 34 · Vascular masses dominate infant mass-forming lesions

Vascular lesions as the most common mass-forming lesions of infancy.

Their broad vascular architecture is not fundamentally different from that seen in adults.

The pediatric emphasis is distribution, evolution and consequences.

Slide 35 · Common cutaneous locations and appearance

Most childhood vascular lesions described here are in the skin.

Face and scalp are prominent sites.

They may be flat or elevated, irregular, and red to blue in appearance.

Slide 36 · Recognizing flat and elevated lesions

Flat vascular lesion

Elevated vascular mass

May present as a broad superficial discoloration.

Produces an appreciable mass above the cutaneous surface.

Some large flat lesions are called port-wine stains.

Some vascular tumors enlarge and later regress.

Surface appearance alone does not resolve exact biological category.

Growth behavior remains an important part of interpretation.

Slide 37 · The natural history may include involution

Infant presentation

→

Enlargement with growth

→

Spontaneous regression

Some hemangiomas grow in parallel with the child.

Many lesions regress spontaneously; The source figure illustrates this.

Regression is common in some lesions, not guaranteed for every vascular malformation.

Slide 38 · Clinical importance beyond appearance

Cutaneous vascular lesions may have substantial cosmetic consequences.

A large or strategically located mass may create functional concerns.

The presence of a vascular lesion can sometimes be part of a hereditary condition.

Slide 39 · Syndromic and familial associations

Von Hippel–Lindau disease as an example of a hereditary association relevant to vascular lesions.

A subset of central nervous system cavernous vascular malformations is familial.

The familial CNS cavernous malformation group is associated with KRIT1, CCM2 or PDCD10 mutations.

These genes pertain to familial CNS cavernous malformations, not all skin hemangiomas.

Slide 40 · Vascular lesion reasoning exercise

Illustrative scenario: An infant has an irregular red-blue facial skin lesion that changes over time.

Question

What is the first useful classification question?

Reasoned interpretation

Determine whether this represents a proliferative vascular tumor or a nonproliferative malformation.

Site and natural history matter; Do not diagnose subtype from color alone.

Slide 41 · Fibrous tumors: A broad mesenchymal spectrum

Fibrous tumors in infants and children are thought to arise from fibroblasts or myofibroblasts.

The spectrum includes sparsely cellular fibromatosis and highly cellular infantile fibrosarcoma.

These entities should not be presumed biologically identical because both contain spindle cells.

Slide 42 · Fibromatosis: Sparse spindle-cell proliferation

Schematic spindle-cell proliferation

Fibromatosis is described as a relatively sparsely cellular spindle-cell proliferation.

Spindle-cell morphology reflects the broad fibroblastic/myofibroblastic category.

A generic spindle-cell schematic does not establish a tissue diagnosis.

Slide 43 · Fibromatosis versus infantile fibrosarcoma

Fibromatosis

Infantile fibrosarcoma

Relatively sparse spindle-cell proliferation.

More cellular lesion; histology can resemble adult fibrosarcoma.

Represents one part of the childhood fibrous-lesion spectrum.

Has its own characteristic molecular and clinical behavior.

Diagnosis requires lesion-specific evaluation.

Its favorable prognosis compared with the adult analogy is noteworthy.

Infantile fibrosarcoma is NOT being reclassified as a benign tumor.

Slide 44 · Histologic resemblance does not predict outcome

Infantile fibrosarcoma may look similar to adult fibrosarcoma under the microscope.

Despite the similarity, infantile fibrosarcoma generally has an excellent prognosis.

Age-specific biological context matters when interpreting aggressive-appearing morphology.

Infantile fibrosarcoma is included as an important differential boundary, not as a benign neoplasm.

Slide 45 · The ETV6::NTRK3 fusion mechanism

T(12;15)(p13;q25)

→

ETV6::NTRK3 fusion

→

Constitutive kinase signaling

ETV6 encodes a transcription factor; NTRK3 encodes the TRKC kinase.

Fusion protein activates oncogenic signaling pathways.

Slide 46 · Fusion-driven signaling in infantile fibrosarcoma

ETV6::NTRK3

→

Constitutive tyrosine kinase

→

RAS–MAPK + PI3K–AKT

These cascades provide a mechanistic link to proliferative signaling.

The diagram summarizes the textbook mechanism, not every molecular interaction.

Slide 47 · A diagnostic and therapeutic molecular example

ETV6::NTRK3 is a characteristic and diagnostically useful fusion in infantile fibrosarcoma.

The fusion helps separate this entity from morphologically overlapping soft-tissue tumors.

Selective NTRK inhibitors can produce major antitumor responses in fusion-positive unresectable cases.

Therapeutic statement is source-derived and is not a treatment guideline.

Slide 48 · Fibrous lesion interpretation

Illustrative scenario: A young child has a highly cellular spindle-cell soft tissue tumor.

Question

Does adult-type histologic resemblance establish a poor prognosis?

Reasoned interpretation

No. Consider infantile fibrosarcoma and the diagnostic role of ETV6::NTRK3.

Infantile fibrosarcoma is a biologically separate tumor rather than a benign lesion.

Slide 49 · Teratomas contain differentiated tissue types

Ectoderm

Mesoderm

Endoderm

Conceptual tissue origins in a teratoma

Teratomas are germ cell neoplasms that may contain tissues from ectodermal, mesodermal and/or endodermal origins.

The constituent tissues can be mature or immature.

Biological interpretation depends partly on tissue maturity and other tumor components.

Slide 50 · Teratoma maturity and biological classification

Mature

Well-differentiated, often cystic; Generally benign in this pediatric context.

Immature

Contains immature tissues and has variable/indeterminate potential.

Malignant

May include another malignant germ cell component, such as yolk sac tumor.

Avoid calling all teratomas benign.

Slide 51 · Mature teratoma: Defining pathology

Mature teratomas are well-differentiated lesions.

They may be cystic.

Different mature tissue types are arranged in a disordered mixture rather than normal organ architecture.

Slide 52 · Immature teratoma: What increases concern

Immature teratomas contain incompletely differentiated tissue elements.

Immature neuroepithelium is a particularly important component.

The extent of immature tissue relates to malignant potential in the chapter’s account.

Slide 53 · Mature, immature and overtly malignant teratoma

Category

Histologic clue

Biological interpretation

Mature

Well-differentiated tissues; often cystic.

Usually benign.

Immature

Immature elements, often neuroepithelial.

Potential correlates with immaturity.

Malignant

Malignant germ cell component may coexist.

Unequivocally malignant.

Slide 54 · Two age-related occurrence peaks

One incidence peak at approximately 2 years of age.

A second peak occurs in late adolescence or early adulthood.

The early peak represents congenital neoplasms; Later lesions may also originate prenatally but grow more slowly.

Slide 55 · Sacrococcygeal teratomas: Epidemiologic context

≥40%

Of childhood teratomas arise at the sacrococcygeal site.

1 in 20,000–40,000

Live births: Reported frequency of sacrococcygeal teratoma.

4:1

Female-to-male predominance.

These are textbook-reported figures, not independently updated surveillance estimates.

Slide 56 · Sacrococcygeal site and congenital anomalies

The sacrococcygeal region is the most frequent location of childhood teratomas.

About 10% are associated with congenital anomalies, particularly hindgut, cloacal or midline defects.

The associated defects are not considered simply the result of local tumor pressure.

Slide 57 · Sacrococcygeal teratoma histologic categories

~75%

Reported as mature teratomas.

~12%

Reported as unequivocally malignant.

Remainder

Reported as immature teratomas.

Approximate textbook estimates for sacrococcygeal lesions; Site- and era-specific.

Slide 58 · Age and behavior in sacrococcygeal tumors

Most benign sacrococcygeal teratomas occur in younger infants, particularly before 4 months.

Children with malignant lesions tend to be somewhat older.

Age adds context but cannot replace histopathologic classification.

Slide 59 · Other pediatric teratoma locations

Gonadal

Testis and ovary.

Central trunk

Mediastinum and retroperitoneum.

Other midline

Head and neck regions.

The source refers to organ-specific chapters for detailed pathology.

Slide 60 · Teratoma classification exercise

Illustrative scenario: A sacrococcygeal mass contains abundant mature epithelial and mesenchymal tissue with focal immature neuroepithelium.

Question

Should this be called a purely mature lesion?

Reasoned interpretation

No. Immature neuroepithelium requires consideration of an immature teratoma and appropriate risk assessment.

No grading thresholds are inferred beyond Key Pathologic Findings in this chapter.

Slide 61 · Integrated comparison of pediatric mass-forming lesions

Lesion group

Key identifying feature

Principal caution

Heterotopia

Normal tissue in an ectopic location.

Can mimic a neoplasm.

Hamartoma

Disordered local overgrowth of native elements.

Clonality may blur taxonomy.

Vascular lesions

Tumor versus malformation biology.

Terminology and evolution vary.

Fibrous lesions

Spindle cells, variable cellularity.

Infantile fibrosarcoma is not simply benign.

Teratoma

Mature/immature germ-layer tissues.

Maturity and malignant components matter.

Categories are conceptually different and not mutually exclusive in all settings.

Slide 62 · A practical classification sequence

Identify tissue type

→

Evaluate location and architecture

→

Classify biological process

→

Assess clinical risk

If native tissue is ectopic, consider heterotopia.

If native tissue forms a disordered overgrowth, consider hamartoma.

For vascular or germ-cell lesions, apply lesion-specific classification.

Slide 63 · Integrated case: The benign-appearing mass

Illustrative scenario: A childhood mass has mature, bland cells but is compressing an adjacent structure.

Question

What conclusion would be unsafe?

Reasoned interpretation

That benign histology guarantees clinical insignificance. Location and mass effect can be decisive.

Management discussion is intentionally general, not a patient-specific recommendation.

Slide 64 · Diagnostic checkpoints for teaching and practice

Keep lesion identity, tissue maturity and anatomical location as separate observations.

Do not equate “hemangioma” with every vascular malformation or “teratoma” with benignity.

Do not borrow adult prognostic expectations for infantile fibrosarcoma.

Use source-specific definitions and specialist evaluation for individual lesions.

Slide 65 · Core synthesis

Heterotopia: Normal tissue, abnormal site; Hamartoma: Native tissue, disordered excess.

Pediatric benign/tumor-like lesions often reflect mesenchymal or developmental processes.

Vascular lesions require biologic subclassification; Fibrous lesions require age-appropriate interpretation.

Teratoma maturity and coexisting malignant elements guide biological assessment.

Histology and clinical consequences are distinct axes of evaluation.

Slide 66 · Primary reference and verification boundaries

Robbins, Cotran & Kumar: Pathologic Basis of Disease, 11th ed. (2026).

Chapter 10: Diseases of Infancy and Childhood, “Tumors and Tumor-Like Lesions,” pp. 432–434.

Content synthesized from the supplied Markdown conversion and directly adjacent subsection text.

Textbook figures and external histology were not reproduced; diagrams are original conceptual schematics.