Lymphocytic panniculitis: an algorithmic approach to lymphocytes in subcutaneous tissue

Abstract

The diagnosis of panniculitis is a relatively rare occurrence for many practising pathologists. The smaller subset of lymphocyte-predominant panniculitis is further complicated by the diagnostic consideration of T cell lymphoma involving the subcutaneous tissue, mimicking inflammatory causes of panniculitis. Accurate classification of the panniculitis is crucial to direct clinical management as treatment options may vary from non-medical therapy to immunosuppressive agents to aggressive chemotherapy. Many diseases show significant overlap in clinical and histological features, making the process of determining a specific diagnosis very challenging. However, with an adequate biopsy including skin and deep subcutaneous tissue, a collaborative effort between clinician and pathologist can often lead to a specific diagnosis. This review provides an algorithmic approach to the diagnosis of lymphocyte-predominant panniculitis, including entities of septal-predominant pattern panniculitis (erythema nodosum, deep necrobiosis lipoidica, morphea profunda and sclerosing panniculitis) and lobular-predominant pattern panniculitis (lupus erythematous panniculitis/lupus profundus, subcutaneous panniculitis-like T cell lymphoma, cutaneous γ-δ T cell lymphoma, Borrelia infection and cold panniculitis).

Insights from Mendelian Interferonopathies: Comparison of CANDLE, SAVI with AGS, Monogenic Lupus

“…Panniculitis has not been reported in SAVI with rare reports in AGS [33] and so far no reports in monoSLE. In contrast to CANDLE, histologic features of SLE panniculitis (SLE profundus) include lobular lymphocytic infiltrates with increased interstitial mucin and hyaline necrosis in subcutaneous tissue [90], suggesting a distinct innate pathogenesis in CANDLE.…”

Septolobular panniculitis in disseminated Lyme borreliosis

“…Despite the positive IgM Lyme serology, other causes of panniculitis must be excluded . In this patient, specific differential considerations can be given to medication‐related panniculitis, lupus profundus and subcutaneous panniculitis‐like T‐cell lymphoma.…”

“…Post‐steroid panniculitis, which occurs following withdrawal of high dose corticosteroids, is extremely rare in adults and the histopathologic features, unlike our case, resemble subcutaneous fat necrosis of the newborn. Other forms of panniculitis should also be considered, such as lupus profundus, which can show significant histopathologic overlap with Borrelia ‐associated panniculitis . Lack of other clinical findings of lupus erythematosus, the negative ANA and presence of lobular neutrophils rendered lupus panniculitis highly unlikely.…”

Panniculitides of particular interest to the rheumatologist

“…When sclerotic changes extend beyond the dermis to involve the subcutaneous tissue, the fascia or the superficial muscle, we refer to deep variant of circumscribed morphea (previously known as subcutaneous morphea or morphea profunda). In contrast, when there is exclusive deep fascia involvement, classification as eosinophilic fasciitis or Shulman's syndrome is more appropriate [20]. Clinically, deep morphea appears in the form of indurated plaques or nodules, frequently located on the upper part of the trunk close to the midline and on the lower limbs (Fig.…”