Subcutaneous panniculitis-like T-cell lymphoma (SCPTCL)

SUBCUTANEOUS PANNICULITIS-LIKE T-CELL LYMPHOMA (SCPTCL) is an uncommon T-cell lymphoma localized to the subcutaneous tissue^{ref1,
ref2,
ref3}.

Epidemiology : the median age of patients is 43 years with a broad range (1-84 years). Females are affected more often than males
Aetiology : ?
Symptoms & signs : multiple, or less often solitary, erythematous to violaceous, deep-seated 0.5-12 cm waxing and waning nodules, resembling lipomas, or plaques are present on the legs>arms>trunk>face. Ulceration and extracutaneous disease are uncommon. SCPTCL produces a lobular panniculitis with little involvement of the reticular dermis and sparing of the papillary dermis. Fever, and hepatosplenomegaly
Laboratory examinations : pancytopenia

cytomorphology : the lymphocytes are pleomorphic varying in size from small to medium and large with dysplastic folded nuclei. The lymphocytes rim the fat spaces producing a lacelike pattern of infiltration and infiltrate small venules, but angiodestructive lesions are not present. Necrosis of fat and/or connective tissue septae is seen in all cases but may be focal. Variable numbers of benign histiocytes are present and exhibit phagocytosis of red blood cells or nuclear debris. Some patients have a systemic hemophagocytic syndrome (HPS) and erythrophagocytosis is seen in the bone marrow, liver or spleen, but tumor is generally not present^ref and is often a fatal complication
immunophenotype : 75% express the aß TcR protein but approximately 25% have a gd phenotype a more aggressive clinical course^{ref1,
ref2,
ref3,
ref4}. The T cells are CD8⁺>CD4^-CD8^- (seen in the gd phenotype) >CD4⁺ and are TIA-1⁺. Most SCPTCL are CD56^-, although SCPTCL with a gd phenotype is more likely to be CD56⁺ and have a more aggressive clinical course

Differential diagnosis :

lupus profundus
eythema nodosum
erythema induratum
cytophagic histiocytic panniculitis (CHP)^{ref1,
ref2,
ref3} (McKee PH. Diseases of the subcutaneous fat. Chapter 10 In Pathology of the Skin with Clinical Correlations. 2nd ed., Mosby-Wolfe; London, UK, 1996, 10.1-10.24 (also Weber-Christian, p.10.5); Dahl PR, Su WPD. Panniculitis. Chapter 24 in Pathology of the Skin, 2nd ed., Farmer ER, Hood AF (eds), McGraw Hill, New York, NY, 2000, pp 453-486). CHP is thought to represent a reactive proliferation of cytophagic histiocytes as a result of an abnormal or exaggerated T-cell immune response. The relationship of CHP to SCPTCL is not clear. SCPTCL with a protracted CHP-like phase has been described (Sajben FP, Schmidt C. Subcutaneous T-cell lymphoma: a case report and additional observations. Cutis.1006;58:297-302). SCPTCL and CHP may represent a continuum with CHP being a "smoldering" lymphoid neoplasm rather than an inflammatory disease^ref1,
ref2, or CHP and SCPTCL may be different diseases^ref. Distinguishing SCPTCL and CHP is difficult. If cytophagocytosis is present with some necrosis and lack of definite cytologic dysplasia in the lymphocytes, CHP should be considered. If systemic symptoms are present, a bone marrow should be performed and examined for erythrophagocytosis. If present this likely has a bad prognosis despite lack of evidence of dysplasia.

Prognosis : there can be nodal dissemination but the poor prognosis is usually due to fulminant hemophagocytosis^{ref1,
ref2,
ref3}. Median survival is usually < 2 years, but occasional patients without hemophagocytosis have had an indolent course and some patients have had prolonged remissions after chemotherapy^ref1,
ref2

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