A Practical Approach to the Diagnosis of Common Hematopoietic and Solid Tumors of Childhood
Case 4 -
D. Ashley Hill, M.D.
Mihaela Onciu M.D.
This five month old female presented acutely with fever,
tachypnea and labored respirations. She was diagnosed with Influenza B and admitted to the hospital.
Born at term with an uneventful neonatal course, she had no significant illnesses prior to admission,
although her mother stated that her breathing had not been "normal" for some time. The family history
was notable for two relatives with a history of childhood cancer including the patient's mother who had
acute B-cell leukemia as a child and a maternal cousin who was being treated for neuroblastoma. A chest
X-ray on admission showed hyperaeration of the left lung. A CT scan showed a markedly emphysematous left
upper lobe with compressive atelectasis of the left lower lobe and mediastinal shift. There were
multiple, fine septations in the hyperinflated lobe with no visible normal lung tissue. The radiographic
differential diagnosis included congenital pulmonary airway malformation (CPAM) and congenital lobar
emphysema. The patient recovered from her upper respiratory infection and returned approximately three
weeks later for resection of the abnormal left upper lobe. At surgery, the left upper lobe showed
massive overinflation with attenuation of the visceral pleura. The upper lobe was dissected off the
lower lobe with ligation of upper lobe branches of the pulmonary vascular structures and the left upper
lobe bronchus. No other cystic abnormalities involving the pleura, mediastinum or left lower lobe were
The left upper lobe measured 11.0 x 7.0 x 1.3 cm.
Sections showed a 6.5 cm diameter cystic lesion in the apex covered by smooth visceral pleura. Multiple
incomplete fibrous septae with mural thicknesses of 0.2 cm or less and collapsed air-filled cysts ranging
from 1.0 to 2.0 cm in diameter were noted. No nodular thickenings or solid areas were seen. The
uninvolved parenchyma showed atelectasis and consolidation.
Sections showed pleural-based cysts whose walls
were variably cellular and lined by a bland low-cuboidal type epithelium. Focal condensations of
primitive stellate, round and spindle-shaped cells were noted beneath the cyst lining cells imparting a
cambium layer-like appearance. The primitive cells showed nuclear hyperchromatism and high
nuclear-to-cytoplasmic ratios and were mitotically active. Loose fibrovascular tissue containing
spindle-shaped cells resembling fibroblasts predominated in the deeper portions of the septae. Small
nodules of primitive cartilage were also seen focally in the cyst walls. The multicystic lesion did not
involve the margins of excision.
Pleuropumonary blastoma, Type I
Following the pathologic diagnosis, further clinical
evaluation included a full body CT scan and head MR. There was no evidence of metastatic disease.
However, a hypodense lesion in the lower pole of the left kidney and jejunal "polyps" were seen. A
subsequent renal ultrasound was performed and the interpretation was a simple renal cyst.
The patient was then followed with serial chest X-rays and CTs. At 4 months post-surgery a CT scan
identified three parenchymal cysts in the remaining left lung ranging from 0.24 to 0.62 cm in diameter,
which in retrospect were there 1 month post-surgery. Two cysts in the left kidney were also noted. At 6
months post-surgery CT scans showed 4 distinct cystic lesions in the left lung ranging from 0.27 to 2.1
cm in diameter, and two distinct cystic lesions in the right lung, measuring 0.24 and 0.57 cm in
diameter. The left kidney contained three distinct cysts, each measuring 1.9 cm in maximum dimension.
In addition, small bowel polyps were also seen. A left partial nephrectomy and wedge resections of the
left lower lobe lung cysts were performed.
Gross examination of the kidney specimen showed a subcapsular multilocular cyst measuring 1 cm.
Microscopically this lesion was a multilocular cyst lined by bland, flattened cuboidal epithelium. The
cyst walls contained loosely arranged primitive mesenchymal cells with a stellate configuration in a
myxoid background. No cambium layer was seen. Within the parenchyma adjacent to the cysts, rare
abortive glomeruli and dilated, irregular tubules were seen similar to those seen in embryologic renal
dysplasia. No blastema or cartilage was present. The wedge biopsies of lung showed subpleural,
thin-walled cysts, ranging from 1.2 and 1.5 cm in greatest dimension. Microscopically the cysts
resembled those in the left upper lobe specimen. There were subepithelial condensations of spindle cells
showing rare mitotic activity. No cartilage was present. Focally, the subepithelial spindle cells
contained abundant pink cytoplasm suggestive of rhabdomyoblastic differentiation. These cells were
The patient was started on Vincristine, Actinomycin D, Cyclophosphamide alternating with Carboplatin,
Etoposide and Ifosfamide following her second surgery. She is currently well 21 months after her
original diagnosis. She has persistent but stable right lung cysts that are being followed
Lung, left upper and lower lobes, excisions
- Pleuropulmonary blastoma, Type I, multifocal
Kidney, left, partial nephrectomy
- Cystic nephroma of childhood
Pleuropulmonary blastoma is a rare pediatric lung cancer that almost exclusively affects children less
than 5 years of age. PPB was initially described as a unique entity in 1988 by L.P. Dehner
and colleagues. Approximately 15 to 20 children in the United States and 30 to 40 children worldwide are
diagnosed with PPB annually. Despite its rarity, the tumor has been extensively studied and is well
characterized from a clinical and pathologic perspective. I have included it for discussion here because
of its interesting relationship with the other tumors described above. Prior to the introduction of the
PPB as a distinct entity, this tumor had been reported in the earlier literature as pulmonary blastoma,
sarcoma arising in mesenchymal cystic hamartoma, embryonal sarcoma, malignant mesenchymoma, primary
pulmonary rhabdomyosarcoma and rhabdomyosarcoma arising in congenital adenomatoid malformation or
bronchogenic cyst. In today's literature there is still some confusion about the distinction between the
early stage PPB and cystic adenomatoid malformation type IV. The establishment of the Pleuropulmonary
Blastoma Registry by Jack Priest, M.D. and colleagues has improved our understanding of this unique
developmental neoplasm. The registry website serves as an important resource for both physicians and
One of the important pathologic features of the PPB is that this neoplasm manifests itself as one of
three morphologic subtypes which correlate with the age at diagnosis and outcome (Table 4.1). In its
earliest form, PPB is a multilocular cyst composed of mesenchymal tumor cells beneath an intact, benign
epithelium (Type I PPB). In later stages the mesenchymal components overgrow the epithelial cysts into
an overtly malignant cystic and solid (Type II) or purely solid neoplasm (Type III). The pathologic
categories of PPB appear to be related along a spectrum showing increased biologic aggressiveness as the
neoplasm progressively acquires solid features. It is interesting to note that the median ages of the
three types show PPB type I occurring in the youngest group and type III occurring in the oldest group
with type II tumors in the intermediate group. The clinical progression of a type I to a type II or type
III PPB within a given patient has been well documented in those cases in which a previously diagnosed
"congenital lung cyst" or "congenital cystic adenomatoid malformation" was followed a year or two later
by a type II or III PPB. Wright has documented the progression of a type I PPB, originally interpreted
as a cystic hamartoma which recurred as a solid type III PPB. These types of cases have caused some
authors to caution against non-operative management of lung cysts in young children. Table 4.2
highlights the progression from "benign cystic disease" to PPB in 21 Registry cases.
Type I PPB (27% of all PPB) occurs on average in a younger age
group compared to the other types (median age 9 months; range 0 to 37 months). These patients may
present with dyspnea, pneumothorax or compression of intrathoracic structures, with or without
mediastinal shift, by large hyperinflated cyst(s). Type I PPB is a potentially deceptive lesion as it is
composed of benign-appearing, peripherally-located, thin-walled cyst(s) often submitted to the pathology
laboratory as a "congenital lung cyst." There are no grossly observable solid, nodular or plaque-like
thickenings in this collapsed multicystic structure. The neoplastic component of the type I PPB is only
apparent microscopically with the identification of primitive tumor cells beneath a benign surface
epithelium. Classically the tumor cells are arranged similar to a cambium layer of botryoid
rhabdomyosarcoma (several layers of primitive, mitotically active tumor cells beneath an intact
epithelium). The subepithelial tumor cells contain small, rounded or spindled hyperchromatic nuclei.
Elongated strap cells with abundant eosinophilic cytoplasm or large rounded cells with similar appearing
cytoplasm like those seen in an embryonal rhabdomyosarcoma can be seen in some but not all cases.
Skeletal muscle differentiation can also be demonstrated by immunohistochemical stains for desmin,
muscle-specific actin, myogenin or Myo-D1. These stains will highlight both the cells with cytological
attributes of rhabdomyoblasts as well as in scattered primitive subepithelial cells. Some tumors also
have nodules of immature cartilage in the cyst walls.
The present case illustrates one of the challenges in the diagnosing a type I PPB. In our experience
many type I PPB do not have an extensive subepithelial zone of tumor cells but rather are characterized
by widely scattered and subtle collections of primitive small cells in a subepithelial location within an
otherwise bland, hypocellular septal stroma. These diminutive subepithelial buds of primitive small
cells and/or nodules of immature cartilage may or may not be accompanied by more compelling foci of dense
subepithelial or septal mixed round and spindle cells. Extensive sampling of the cyst walls in these
cases is essential. The primitive small and/or spindle cells in these examples may show immunoperoxidase
staining for one or another of the muscle markers, however, the absence of myogenic immunophenotype does
not preclude the diagnosis of Type I PPB in our experience.
Based on a recent unpublished review of 41 Type I PPBs we have observed that early Type I PPBs in
neonates have a much more uniform distribution of tumor cells. In these examples, de novo regressive
changes such as cyst wall necrosis are common. We hypothesize that these regressive features may be
responsible for the variability of tumor burden seen in later stages of Type I disease. The factors that
control the balance between continued proliferation (and disease progression) and regression are poorly
understood but may be important in predicting which Type I tumors will require adjuvant chemotherapy.
Type II PPB occurs in somewhat older children (median 31 months,
range 6 to 64) and represents 41% of all PPB. A cystic pattern similar to that seen in the type I PPB is
identified either grossly (when this component is substantial) or microscopically with remnants of septa
with cambium layers in an otherwise predominantly solid neoplasm. When cystic areas are noted in the
gross examination, they are generally characterized as thickened or plaque-like septae. Microscopically
the type II PPB is composed of an overgrowth of rhabdomyosarcomatous, spindle cell sarcoma or
blastematous elements forming solid confluent areas of tumor with varying amounts of residual septal
cystic tissue remaining. Anaplastic tumor cells can be seen in the solid components of type II tumors.
Type III PPB accounts for the other 32% of cases and occurs in
children with a median age of 42 months (range 1 to 147 months). These patients present with fever,
cough, chest and abdominal pain, dyspnea and weight loss. Radiographically, these tumors are typically
heterogeneous solid masses with or without involvement of chest wall or mediastinal structures. The
entire hemi-thorax may be opacified by the mass. Grossly, a well-circumscribed, solid, mucoid, tan-white
and friable mass with pleural attachments involving a lobe or entire lung is seen. Hemorrhage and
necrosis account in part for the friability of the tumor. If the tumor has extended into the surrounding
pleural space, the resection specimen may be submitted in a piecemeal fashion. Microscopically the type
III PPB (and solid areas of the type II PPB) shows one or more of four basic histologic patterns which
may blend into each other: (1) cohesive aggregates of primitive small cells with hyperchromatic nuclei,
high nuclear-to-cytoplasmic ratio and brisk mitoses resembling the blastema of a Wilms; (2) spindled,
stellate and small ovoid cells in a variably prominent myxoid stroma resembling rhabdomyosarcoma; (3)
spindle cell sarcoma resembling synovial sarcoma or congenital-infantile fibrosarcoma; (4) nodules of
immature or overtly malignant cartilage. Individual or groupings of large pleomorphic cells with
atypical mitotic figures are present in many cases. Eosinophilic hyaline bodies are often seen in
association of anaplastic cells. Within any one tumor, not all histologic patterns are equally
represented and one or two patterns may dominate the overall microscopic appearance. Unlike the classic
pulmonary blastoma, the PPB does not have a malignant epithelial component.
Immunohistochemistry and genetic analysis are generally unnecessary to establish the diagnosis of PPB
in the majority of the cases. PPB commonly shows staining for desmin and myogenin in areas of obvious
rhabdomyosarcomatous differentiation. S100 protein is typically limited to the cartilaginous nodules.
When subepithelial foci of primitive cells are identified in a suspected type I PPB, these cells are
inconsistently immunoreactive for desmin and/or myogenin in the absence of apparent rhabdomyoblasts.
These primitive cells like the other septal stromal cells are positive for vimentin. Cytokeratin
highlights the flattened to cuboidal epithelial cells but is negative in the tumor cells. Fluorescence
in situ hybridization (FISH) can identify trisomy 8, a common abnormality in
PPBs. Trisomy 8 is not specific to the PPB since it has been observed in embryonal rhabdomyosarcoma,
granulocytic sarcoma, Ewing sarcoma and congenital-infantile fibrosarcoma. Trisomy 2, and p53
mutations/deletions in a subset of cases have also been described.
Because there is significant variability in the morphologic appearance of PPB, the differential
diagnosis is broad. For type I PPBs, the distinction from a multilocular pulmonary cyst in the category
of congenital pulmonary airway malformations (CPAM) type 1 or 4 is critical to the appropriate management
of the patient. Both CPAM and type I PPB both occur in infants and young children and can either be
discovered incidentally or present with respiratory distress. The index of suspicion for PPB must be
extremely high when encountering a collapsed multilocular cyst from the lung of a young child. We
advocate the approach that all lung multilocular cysts in infants and children less than 2 years old are
type I PPB until proven otherwise. Proving otherwise is best accomplished by submission of the entire
gross specimen for histologic examination (or a substantial portion of it). Many examples of type I PPB
have bland histologic features. However, if one notes the presence of dense subepithelial or septal
spindle cells with or without nodules of immature cartilage, a diagnosis of type 1 PPB is appropriate.
Ancillary studies to differentiate benign cysts from type I PPB are only helpful if they are positive,
since the absence of muscle differentiation in a primitive cell component does not preclude the
pathologic diagnosis of type I PPB. The utility of FISH in detecting the characteristic trisomy 8 in
type I PPB with few neoplastic cells is uncertain.
Type II tumors should be distinguished from type I tumors by the presence of a solid component
represented by grossly observable thickened, nodular or plaque-like areas containing sarcomatous or
blastematous elements or microscopic evidence of a confluent overgrowth of overtly malignant elements
widely expanding the septae. Anaplastic cells are typically limited to solid components of type II and
III PPB and have only rarely been seen in Type I tumors. The importance of this distinction between type
I and type II tumors is the difference in prognosis and treatment regimen.
In type II and type III PPB, there is generally little question about the pathologic process being
benign or malignant. Depending on the predominance of one or more sarcomatous or blastemal elements, the
differential diagnosis includes primary and metastatic rhabdomyosarcoma, malignant teratoma, synovial
sarcoma, congenital-infantile fibrosarcoma and other spindle cell or undifferentiated sarcomas. In solid
tumors with a predominant blastemal pattern, metastatic Wilms tumor may be considered. Cytokeratin
immunohistochemistry (PPB is negative for cytokeratin) and renal ultrasound would be helpful in making
this latter distinction.
Biological Behavior, Treatment and Outcome
Type II and type III PPB are bulky tumors that can spread through direct extension into adjacent
uninvolved lung, pleura, diaphragm, chest wall and mediastinal structures or by hematogenous
dissemination. The most common sites for distant metastases are the brain (26/172, 15%), bone (10/172,
6%), liver (7/172, 4%) and less commonly adrenal, eye, spinal cord, ovary and pancreas. Because of the
predilection for brain metastasis, a head MR is recommended as part of the initial staging evaluation and
Treatment for PPB is based on a combined, multimodality approach similar to other pediatric sarcoma
regimens. Additional details and dose regimens is given on the PPB Registry website (http://www.ppbregistry.org). Type I PPB is treated with complete
surgical removal and adjuvant chemotherapy. With chemotherapy, the 5-year overall survival for this
subgroup is over 90%. There continues to be some debate regarding the need for adjuvant therapy in type
I PPB. A recent analysis of Registry patients has shown that there is a statistically significant
difference in recurrence free survival in patients who receive adjuvant chemotherapy (p=0.01). When
patients with Type I PPB have a recurrence, it has a Type II or Type III pattern. The salvage rate for
recurrent PPB is poor. Only 33% of patients with recurrence following Type I PPB survive. The
alternative to chemotherapy is a rigorous radiographic follow-up schedule. Hopefully future studies of
Type I PPB will allow for more accurate prediction of who is most at risk for recurrence. Despite the
fact that children with Types II and III PPB are subject to an aggressive chemotherapy regimen, the
5-year overall survival rates for Type II and Type III PPB are only 60% and 45%, respectively (PPB
Registry unpublished data). The decision to give radiation therapy is individualized.
PPB Family Cancer Syndrome
One of the
key observations in children with PPB was the recognition that PPB was a feature of a unique cancer
predisposition syndrome. An estimated 25 to 35% of patients with PPB have multifocal disease and/or
other rare benign or malignant neoplasms, dysplasias and/or hyperplasias in themselves or their close
relatives. These entities include other PPBs, lung cysts, embryonal rhabdomyosarcoma, Wilms
tumor and variants (cystic nephroma, cystic partially differentiated nephroblastoma,
nephroblastomatosis), medulloblastoma, gonadal germ cell and stromal tumors, primitive retinal tumor,
thyroid cancers and nodular hyperplasia, juvenile intestinal polyps, sarcomas and hematopoietic
malignancies. This observation is remarkable not only for the rarity of these neoplasms in the
general population, but also for these entities having a common association with organ development.
- PPB is divided into three clinicopathologic types that represent a continuum of
histologic and biologic progression
- Type I PPB is a neoplasm whose diagnostic features can be subtle and tumor cells may
be focally present; extensive sampling of the cyst walls is critical
- Type II PPB can be distinguished from Type I PPB by the presence of grossly identifiable
thickened plaque-like, nodular or solid areas containing rhabdomyosarcomatous,
blastematous or spindle cell sarcomatous elements or by microscopically evident
overgrowth of malignant elements in septa
- Type II and III PPB have a predilection for metastasizing to brain
- PPB appears to be part of a familial cancer syndrome which can manifest as
multifocal PPB or in association with other neoplasms, dysplasia and/or hyperplasias
in patients or their close relatives
- Association with cystic nephroma is common
Table 4.1 Age at Presentation for the Three Clinicopathologic Subtypes of PPB
|PPB Type ||Median Age at Diagnosis ||Survival|
|I ||9 months ||90%|
|II ||31 months ||60%|
|III ||42 months ||45%|
Overall Survival estimates by Kaplan-Meier at 5 years post-diagnosis
Age at presentation data courtesy of Jack Priest M.D., PPB Registry http://www.ppbregistry.org
Table 4.2: Progression of "benign cystic disease" to PPB in 21 Registry cases
DOD = dead of disease, NED = no evidence of disease; Data courtesy of Jack Priest, M.D., PPB Registry, 5/2003
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clinicopathologic study of 50 cases. Cancer 1997;80:147-61.
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to type III (solid). Cancer 2000;88:2853-8.
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pleuropulmonary blastoma. Cancer
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HEMATOPOIETIC NEOPLASMS (NON-HODGKIN LYMPHOMA)
Hematopoietic (CD45-Positive) Tumors Encountered/Reported in Childhood
(* Neoplasms most commonly encountered)
- Acute lymphoblastic leukemia/ lymphoblastic lymphoma*
- Non-Hodgkin lymphoma
- ALCL (ALK positive)*
- Burkitt lymphoma*
- Diffuse large B-cell lymphoma (including primary mediastinal variant)*
- Peripheral T-cell lymphomas
- Low-grade B-cell lymphoma
- Follicular lymphoma
- Marginal zone lymphoma
- Chronic lymphocytic leukemia
- Hodgkin lymphoma*
- Classical type
- Nodular sclerosis
- Mixed cellularity
- Nodular lymphocyte predominance
- Acute myeloid leukemias/ myeloid sarcomas*
- Chronic myeloproliferative disorders
- Myeloproliferative/myelodysplastic syndromes
- Juvenile myelomonocytic leukemia*
- Myelodysplastic syndromes (association with myeloid sarcoma)
- Monocyte/macrophage lineage
- Acute monoblastic/monocytic/myelomonocytic leukemia/ monoblastic sarcoma*
- Histiocytic sarcoma
- Rosai-Dorfman disease (nodal/extranodal)*
- Solitary histiocytoma of macrophage lineage
- Dendritic cell lineage
- Langerhans cell histiocytosis*
- Langerhans cell sarcoma
- Juvenile xanthogranuloma (dermal dendritic cell origin)*
- Dendritic reticulum cell tumor/sarcoma
- Follicular dendritic cell (FDRC) (nodal/extranodal)
- Interdigitating reticulum cell (IDRC)
Immunophenotypic Algorythm for the Differential Diagnosis of the Most Common
Pediatric Non-Hodgkin Lymphomas
Materials Required for the Diagnostic Work-up of a Hematopoietic Neoplasm
- Formalin-fixed or B5-fixed tissue - may be used for :
- Morphologic examination (tumor cell cytology, tumor growth pattern)
- Immunohistochemical staining (for most antigens critical for a diagnostic work-up).
- In situ hybridization (including light microscopy and interphase FISH)
- This test cannot be performed in tissue that has been decalcified using acid or fixed in B5 fixative.
- Molecular testing (nucleic acid yield considerably reduced by B5 fixation) - the recovery rate for nucleic acids depends of length of fixation in formalin (one day of fixation is ideal).
- DNA-based (PCR, Southern blotting)
- RNA-based (RT-PCR) - 60-70% success in good laboratories
- Fresh tissue (hold in sterile saline, RPMI or under saline-soaked gauze) - may be used for:
3. Touch imprints, smears or cytospins (air dried):
- Flow cytometry
- Conventional cytogenetics
- Metaphase FISH
- Molecular analysis (fresh or snap frozen)
- DNA-based (PCR, Southern blotting).
- RNA-based (RT-PCR) - ideal sample is fresh or frozen
a. Morphologic examination (tumor cell cytology)
b. Interphase FISH (requires recently prepared smears or smears maintained in freezer)
c. Immunohistochemical examination (cold-acetone fixed smears or cytospins prefered)
d. Molecular analysis
i. DNA based - PCR (limited number of laboratories)
The minimum information required to diagnose and classify any lymphoma includes morphologic and immunophenotypic data. For the diagnosis of some neoplasms (e.g. posttransplant lymphoproliferative disorders, T/NK lymphoma of nasal type) documentation of EBV positivity in the tumor cells is critical for diagnosis. This can be most reliably examined used an in situ hybridization assay for EBER. Molecular analysis for immunoglobulin or T-cell receptor genes is less commonly required in the pediatric setting, where most lymphomas are of high-grade and therefore easy to diagnose by morphologic examination. However, a small subset of low-grade lymphomas may require such analysis. Lastly, demonstration of the t(8;14)(q24;q32) chromosomal translocation or of one of its variants is highly desirable in Burkitt lymphoma (although the diagnosis can and is often made without that information). Therefore, if only a small amount of tumor tissue is available, formalin fixation followed by paraffin-embedding will provide the broadest coverage for all these needs. If plenty of tissue is available and a preliminary touch imprint raises the suspicion for lymphoma, portions of the material should be fixed in formalin, snap frozen and stored for any possible molecular analysis, and submitted fresh to the cytogenetics and flow cytometry laboratories (depending on the facilities available in each institution). If there is no clear-cut lymphoma in the preliminary assessment, material should be sent to Microbiology as well. The tissue should be handled under sterile conditions until the triage is completed (at a minimum, samples for Microbiology and Cytogenetics require sterile handling).