Università degli Studi di Padova Dipartimento di Medicina Sezione di Anatomia Patologica Generale e Citopatologia

Adipocytic Tumours in children

Emphasis Rita Alaggio 1

Emphasis 2 Basel Seminars in Pathology Paediatric Pathology & Genetics Basel, June 22nd – 25th, 2016 Outline

. Classification of adipocytic tumors . Lipoblastoma . Lipoblastoma: Differential Diagnostic Challenges . Liposarcoma Emphasis 1

Emphasis 2 WHO 2013 Classification

BENIGN . Lipoma . Lipoblastomatosis . Lipomatosis of Nerve . Lipoblastoma . Angiomyolipoma . Myolipoma of soft tissue

. Chondroid lipoma Emphasis . Spindle cell/Pleomorphic lipoma 1 . Hybernoma

MALIGNANT Emphasis . Atypical lipomatous tumor 2 . Dedifferentiated liposarcoma . Myxoid liposarcoma . Pleomorphic liposarcoma WHO 2013 Classification

BENIGN . Lipoma . Lipoblastomatosis . Lipomatosis of Nerve . Lipoblastoma . Angiomyolipoma . Myolipoma of soft tissue

. Chondroid lipoma Emphasis . Spindle cell/Pleomorphic lipoma 1 . Hybernoma

MALIGNANT Emphasis . Atypical lipomatous tumor 2 . Dedifferentiated liposarcoma . Myxoid liposarcoma . Pleomorphic liposarcoma Outline

. Classification of adipocytic tumors . Lipoblastoma . Lipoblastoma: Differential Diagnostic Challenges . Liposarcoma

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Case 1 Multivacuolated and univacuolated lipoblasts Clinical History

. Boy, 1.5 yr . expanding mass in the paravertebral region . Main diameter 3 cm

Emphasis . Treatment: resection 1

Emphasis 2 Clinical History

. Boy, 1.5 yr . expanding mass in the paravertebral region . Main diameter 3 cm

Emphasis . Treatment: resection 1

Emphasis 2 Diagnosis: Lipoblastoma Lipoblastoma

Lipoblastoma, a benign neoplasm of embryonal white fat, is a localized or diffuse (lipoblastomatosis) tumor with a tendency for local recurrence if incompletely excised.

- WHO, 2013 Emphasis 1

Emphasis 2 Lipoblastoma Clinical Features . 90% before 3 years . 40% 1st year of life . Rare in adolescents and adults . Sex: male predilection . Site: trunk, extremities Emphasis – Others: retroperitoneum, pelvis, abdomen, 1 head/neck, organs (lung, heart) Emphasis . Benign clinical course 2 – 13-46% of relapse in incomplete resection

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Lipoblastoma (Courtesy of C. Coffin) Emphasis 1

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Lipoblastomatosis (Courtesy of C. Coffin) Lipoblastoma Histology

. Lobulated architecture with fibrovascular septa . Lipoblasts in various stages of differentiation to mature fat with orientation from periphery to the center: – primitive stellate or spindle cells – multivacuolate lipoblasts Emphasis – signet ring cells 1 – Floret cells – Hibernoma like cells Emphasis . Myxoid foci with plexiform 2 vascular pattern, primitive mesenchymal cells . Chronic inflammation, mast cells . Fibrolipoma-like areas possible

Lipoblastoma Histology

. Lobulated architecture with fibrovascular septa . Lipoblasts in various stages of differentiation to mature fat with orientation from periphery to the center: – primitive stellate or spindle cells – multivacuolate lipoblasts Emphasis – signet ring cells 1 – Floret cells – Hibernoma like cells Emphasis . Myxoid foci with plexiform 2 vascular pattern, primitive mesenchymal cells . Chronic inflammation, mast cells . Fibrolipoma-like areas possible

Lipoblastoma Histology

. Lobulated architecture with fibrovascular septa . Lipoblasts in various stages of differentiation to mature fat with orientation from periphery to the center: – primitive stellate or spindle cells – multivacuolate lipoblasts Emphasis – signet ring cells 1 – Floret cells – Hibernoma like cells Emphasis . Myxoid foci with plexiform 2 vascular pattern, primitive mesenchymal cells . Fibrolipoma-like areas (eg in maturing lipoblastoma) . Chronic inflammation, mast cells

Abdominal Lipoblastoma, age 2 yr. Resection

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Emphasis 2 Abdominal Lipoblastoma, age 2 yr. Recurrence, 5yr

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Emphasis 2 Lipoblastoma Immunohistochemistry

• S100, CD34: positive nonspecific • Desmin: in primitive mesenchymal cells: a potential pitfall • PLAG1 protein: not liable Emphasis • p16: negative 1

Emphasis 2 Desmin p16 -ve

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p16 +ve (2 cases/30) S100 Lipoblastoma (Cappellesso et al Hum Pathol 2016) Lipoblastoma Genetics • Chromosome 8 aberrations typical, including extra copies in 10-15% • Breakpoints cluster to 8q11-13 involving PLAG1 in 8q12.1 • Translocation partners vary: Emphasis – 3q12-13, COL1A2 in 7q21.3 1 – HAS2 in 8q24.13 Emphasis – rarely COL3A1 and RAB2A* 2 – others *Yoshida et al. Genes, Chromosomes & Cancer 53:606–611 (2014) Lipoblastoma: Genetic Alterations

Chromosomal Rearrangements Increase of PLAG1 copy number

IGF2 Activation

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Adipocytes Proliferation Chromosomal Rearrangements of PLAG1

HAS2 (hyaluronic acid synthase 2) COL1A2 (collagen 1 alpha 2) Check and transport of Ialuronic Acid Involved in the formation of the collagen in connective tissue, bone and tendons

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Emphasis 2 Potential role in collagen septae Potential role in the genesis of myxoid formation component ? ? Lipoblastoma Associated Conditions • Developmental delay or abnormalities • Congenital malformations • Seizures • Sturge-Weber syndrome Emphasis • Autism 1

Emphasis • Familial “lipomas” 2 Outline

. Classification of adipocytic tumors . Lipoblastoma . Lipoblastoma: Differential Diagnostic Challenges . Liposarcoma Emphasis 1

Emphasis 2 Lipoblastoma Differential Diagnostic Challenges

• Lipoma and variants • Primitive myxoid mesenchymal tumor of infancy

• Lipofibromatosis Emphasis 1 • Fibrous Hamartoma Emphasis • Liposarcomas, especially myxoid and 2 myxoid-pleomorphic • Other fatty and myxoid tumors Emphasis 1

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Lipoma Hibernoma Genetic aberrations in pediatric lipoma

. Similar to adult lipomas . In literature less than 30 pediatric lipomas investigated: . 11 with aberrations of the 12q14–q15 region, with rearrangement of the HMGA2 gene in 3, 1 with anomaly of 6p21 region, resulting in a rearrangement of HMGA1 . NFIB identified as a fusion partner of HMGA2 in pediatric lipoma. – NFIB is a regulator of adipocyte differentiation; its inhibition Emphasis suppresses induction of adipogenic transcription factors, 1 (PPARγ, C/EBPa etc), and reduces accumulation of lipids during differentiation. Emphasis 2

Cancer Genetics 208 (2015) 469–481 Lipoblastoma Differential Diagnostic Challenges

• Lipoma and variants • Primitive myxoid mesenchymal tumor of infancy

• Lipofibromatosis Emphasis 1 • Fibrous Hamartoma Emphasis • Liposarcomas, especially myxoid and 2 myxoid-pleomorphic • Other fatty and myxoid tumors Emphasis 1

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Vimentin Primitive myxoid mesenchymal tumor of infancy

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Initial diagnosis of Lipoblastoma (2/30 cases in Italian series) Lipoblastoma Differential Diagnostic Challenges

• Lipoma and variants • Fibrous Hamartoma • Primitive myxoid mesenchymal tumor of

infancy Emphasis 1 • Lipofibromatosis Emphasis • Liposarcomas, especially myxoid and 2 myxoid-pleomorphic • Other fatty and myxoid tumors Emphasis 1

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Emphasis 2 Fibrous Hamartoma

. In our series 2 originally diagnosed as lipoblastoma (out of 30 lipoblastomas) . Slight male predilection . Site: axilla, upper extremities, trunk, groin, external genitalia . poorly circumscribed, nodular lesion Emphasis . Organoid lesion, 3 components 1 – Dense fibrous trabeculae

– Primitive mesenchymal cells in nests and bands in the Emphasis context of a myxoid matrix 2 – Mature adipose tissue . Rare multicentric cases Emphasis 1

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Emphasis 2 Lipofibromatosis Histology

. Abundant adipose tissue (>50%) . Slender fascicles of fibroblasts among the adipose lobules . Myxoid component . lipoblast-like cells at the periphery along the fibrous septae Emphasis . Infiltrative growth pattern with entrapment of nerve 1 trunks and muscle Emphasis . Dendritic cells (occasional) 2 . DD with Lipoblastoma: more prominent connectival component and fibroblastic proliferation

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Emphasis 2 Lipofibromatosis Clinical Features

. Myofibroblastic lesion in the past diagnosed as: fibrous hamartoma, fibromatosis, CIFS, lipoblastoma e calcifying aponeurotic fibroma . Frequently congenital . Site: extremities (frequent), thorax, abdomen, Emphasis head (less frequent) 1 . Tendency to relapse Emphasis . Treatment: conservative surgery 2 Lipofibromatosis Molecular/Cytogenetic Features

NTRK1 Associated Gene Fusions in Pediatric Fibroblastic / Myofibroblastic Neoplasms: A Molecular Study of 58 Cases

3 LPF with TPM3-NTRK1 NTRK1 by IHC strong expression 18 LPFs recurrent complex FISH abnormalities at the 1q22-23.1 locus (including NTRK1 and a number of known NTRK1-fusion partners in other cancers) Emphasis 1 10/11 FHI recurrent abnormalities in the same 1q22-23.1 region. Emphasis 2

Agaram NP et al. USCAP 2016

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LIPOSARCOMA Outline

. Classification of adipocytic tumors . Lipoblastoma . Lipoblastoma: Differential Diagnostic Challenges . Liposarcoma

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Emphasis 2 Liposarcoma in children

. Extremely rare in pediatric patients (2% of sarcomas) . Distribution among soft tissue sarcomas: 5%, 6%, 22%, and 66% in age categories: <5 years, 5–9 years, 10–14 years, and 15–19 years, respectively (SEER data). . Most frequent histotype represented by Myxoid Liposarcoma (MLPS)* . Prognosis for conventional MLPS in young patients very favorable* . Progression to Round cell-LPS very uncommon in MLPS in young patients Emphasis . A subset of LPS show features of a Pleomorphic-MLPS, is typical of 1 mediastinal region, with aggressive clinical behaviour. . Spindle cell-LPS also present (not clear if they belong to MLPS) Emphasis . Lipoma-like and pleomorphic LPS exceptional in children 2

*Alaggio R, Liposarcomas in young patients: a study of 82 cases occurring in patients younger than 22 years of age.Am J Surg Pathol. 2009 May;33(5):645-58.

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Myxoid Liposarcoma (60 cases: 10-22y, M:F=2:1) Emphasis 1

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Atypical lipomatous tumor (4 cases: 12-19y, M:F=1:1) Emphasis 1

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Pleomorphic Liposarcoma (2 cases: 5-21y, M:F=1:1) . Male, 10 year-old . Familiar/Personal history negative . Mass in the back noted few months before and recently

increased in size. Emphasis 1

Emphasis 2 MRI solid lesion deeply located in the subcutis, strongly adherent to the fascia.

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Emphasis 2 Treatment Primary excision with macroscopic residual disease. After the histological diagnosis, the child underwent a primary Emphasis re-excision. 1

Emphasis 2 The mass (main diameter 3.6 cm) was completely excised

The child is alive and disease-

free after 8 yr. Emphasis 1

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Spindle cell Liposarcoma (6 cases: 11-17y, M:F=1:5) Emphasis 1

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Emphasis 2 Important differential diagnosis Spindle cell lipoma

Typical of adult age Bland cytology Nuclear palisading Ropey collagen bundles Emphasis Mastocytes 1 CD34+++

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Pleomorphic Myxoid Liposarcoma (10 cases: 10-22y, M:F=2:3) Emphasis 1

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Emphasis 2 Outcome

M/RCLPS P-MLPS SC-LPS ALT/DL PLPS

Follow-up 31/60 (36-108 6/10 (8- 4/6 (12-108 4/4 (36-108 1/2 (72 mos) mos; median 108 mos; mos; mos; 72 mos) median 36 median 42 median 72 mos) mos) mos) ANED 29/31 (94%) 1/6 (17%) 3/4 (75%) 4/4 (100%) 1/1 (100%)

AWD 1/31 (3%) 1/6 (17%) 1/4 (25%) 0/4 (0%) 0/1 (0%) Emphasis 1 DOD 1/31 (3%) 4/6 (67%) 0/4 (0%) 0/4 (0%) 0/1 (0%)

Emphasis LR 3/31 (9%) 3/4 (75%) 1/4 (25%) 2/4 (50%) 0/1 (0%) 2

Mets 0/31 (0%0 2/4 (50%) 1/4 (25%) 0/4 (0%) 0/1 (0%) Pediatric Liposarcoma Genetic aberrations

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CONCLUSIONS Emphasis 2 Differential Diagnosis between Lipoblastoma and Liposarcoma may be challenging Lipoblastoma Myxoid LPS Usual age: Newborn-5 yr Adults

Lobules Well-defined Indistinct Mature fat Central Peripheral, sparse Mucin pools Focal More abundant

Cellularity Low Higher (focal) Emphasis 1 Atypia Absent Present (focal) Mitoses Normal (if any) Abnormal Emphasis Genetics: 8q11-13 12q13 2 PLAG1 DDIT3 t(7;8) t(12;16) or t(12;22)

Courtesy of Cheryl Coffin Lipoblasts do not mean liposarcoma in children

Liposarcoma in children differs from its adult counterpart with minor aggressivity and peculiar histology Emphasis -myxoid with pleomorphic cells 1 -spindle cell Emphasis 2

Fig.14-case 14; mixed myxoid round cell liposarcoma. At the right a myxoid area with intermingled round cell lipoblasts. At the left an area where the cells simulate the appearance and arrangement of a fibrosarcoma

Arthur Purdy Stout. Annals of Surgery, January 1944

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“…in some tumors (myxoid liposarcomas) areas showing a distinct Emphasis spindle cell pattern were present. 2 Unlike the spindle cells of the pleomorphic type, however, the cells were small and slender and generally oriented along a single plane…”

Enzinger &Winslow Virch Arch Path Anat, 1962