Subcutaneous Panniculitis-like T cell Lymphoma

Question 1

What is the definition of Subcutaneous

panniculitis-like T cell lymphoma ?

Answer 1

• cytotoxic T cell lymphoma that preferentially infiltrates subQ tissue
• composed of atypical lymphoid cells of varying sizes with prominent apoptotic debris and tumor cell associated fat necrosis
• IMP:
  
  • cases with G/D receptor expression are excluded and rather classified as primary cutaneous G/D T cell lymphoma
• wide age range (kids to adults)
• prognosis is generally good

Question 2

What is the epidemiology SPTL ?

Answer 2

• rare, accounts for < 1% of lymphomas
• slightly more common in females
• broad patient range
  
  • 20% are < 20 years old
  • median age is 35
  • disease can present in infancy
• 20% of patients have an associated autoimmune disease
  
  • SLE is the most common
  • IMP: d/d is lupus panniculitis, can be difficult to differentiate

Question 3

What is the etiology of SPTL?

Answer 3

• autoimmune disease may play a role in some cases
  
  • SLE has been documented in some cases
• early lesions also appear as lobular panniculitis
• EBV should be negative

Question 4

What is the localization of

SPTL?

Answer 4

• multiple subcutaneous nodules or plaques
• usually absent extracutaneous lesions
• most common:
  
  • extremities
  • trunk
• variable in size but large nodules may become necrotic but ulceration is rare
• usually multiple lesions, rare to just have a single one

Question 5

What are the clinical features of

SPTL?

Answer 5

• symptoms usually relate to the nodules
• systemic symptoms may be seen in up to 50% of people
• lab abnormalities are common
  
  • cytopenias
  • elevated LFTs
• HLH develops in up to 20% of cases
• LN involvement is usually absent
• BM involvement has been rarely described
  
  • usually the cells involve the fat within the marrow space

Question 6

What are the microscopic features

of SPTL ?

Answer 6

• infiltrate involves the fat lobules, usually with sparing of the septa
• IMP: overlying dermis and epidermis are typically spared
• cell size is variable from case to case but is consistent within any particular infiltrate
• cells:
  
  • hyperchromatic, irregular nuclei
  • rim of pale cytoplasm
• rimming of the fat cells is characteristic
• IMP: numerous histiocytes are present particularly in areas of fat infiltration other inflammatory cells are absent
• necrosis and karyorrhexis are common and vascular invasion can be sen
  
  • karyorrhexis helps differentiate this from other lymphomas

Question 7

Which lymphoma may have

panniculitis like features and

should be differentiated from SPTL ?

Answer 7

• Cutaneous G/D T cell lymphoma
  
  • can have panniculitis like features
  • BUT
    
    • also involves the dermis and epidermis
    • may have epidermal ulceration

Question 8

What microscopic feature in Lupus

panniculitis can help differentiate it

from SPTL ?

Answer 8

• the presence of other inflammatory cells in particular
  
  • plasma cells
  • plasmacytoid dendritic cells

Question 9

What is the immunophenotype of

SPTL ?

Answer 9

• mature alpha/beta phenotype
• CD8+
• granzyme B, TIA-1, and perforin +
• beta F1+ and CD56-
  
  • this helps differentiate it from primary cutaneous G/D T cell lymphoma
• CD123 -
  
  • helps differentiate this from the PDCs identified in lupus panniculitis

Question 10

What is the postulated normal counterpart

of SPTL ?

Answer 10

• mature cytotoxic alpha beta T cell

Question 11

What is the genetic profile of

SPTL ?

Answer 11

• neoplastic cells have rearrangement of TR genes
• negative for EBV
• no specific cytogenetic patterns have been identified

Question 12

What are the prognostic and predictive

factors for SPTL ?

Answer 12

• dissemination to LN and other organs is rare
• median 5 year survival is 80%
  
  • but if HLH is present than survival is poor
• treated with combination chemo but new studies suggest just immunosuppression may be helpful
• much better prognosis than cutaneous G/D T cell lymphoma