Discussion:
SPTCL is one of the rarest subtypes of non-Hodgkin lymphoma (NHL) in children, constituting less than 1% of the NHL and the cutaneous lymphomas (2,3) with limited literature in the pediatric population (4,5). No definite gender predilection is noticed, but a slight female predilection is reported by a few studies and is usually associated with good outcomes (5).
Historically, the SPTCL has two subtypes based on T-cell phenotypes – alpha/beta (α/β) with better prognosis and gamma/delta (γ/δ) with poor outcome (3). The European Organization for Research and Treatment of Cancer (EORTC) classification (2005) modified this categorization and advocated the use of α/β T-cell phenotype for SPTCL only and described γ/δ T-cell phenotype as a distinct cutaneous T-cell lymphoma (6). On immunochemistry, the malignant T-cells in SPTCL are CD8+ve, CD3+ve, beta-F1+ve, CD4-ve, and CD56-ve. The γ/δ T-cell phenotype cutaneous T-cell lymphoma is CD56+ve, while beta-F1-ve, and CD4 and CD8 are negative in most cases (3). Histopathology with immunohistochemistry is the gold standard for the diagnosis and is confirmatory in almost all cases (5).
The histological findings include T-cells and macrophages infiltrating subcutaneous fat lobules with relative sparing of the dermis and epidermis simulating panniculitis. The malignant T-cell infiltration of the hypodermic soft tissue in SPTCL incites an inflammatory response very similar to panniculitis (7,8). The inflammatory change can involve a single site or be multicentric, presenting as soft tissue nodules, plaques, edema, discoloration, and itch (5). Compared to young infants, older children with SPTCL present frequently with fever and weight loss (90% vs 40%) and have a higher association with HLH (45.5% vs 20%) (1).
Ultrasound is the initial imaging modality of choice owing to the superficial location and typically demonstrates vague inflammatory changes with or without regional lymphadenopathy (9). CT/MRI may help to determine the extent of inflammatory changes, evaluate deeper structures, underlying masses, and loco-regional lymphadenopathy (3,10). FDG-PET is considered the most useful imaging modality, integrating both anatomical and functional assessment. (11,12). FDG-PET demonstrates the distribution and uptake of the FDG at the primary site and any involvement of the distant sites, visceral organs, and lymph nodes, allowing for accurate pre-treatment staging (3,11). It can also help to guide the optimal biopsy site based on the metabolic activity and FDG avidity (12). Post-therapy FDG-PET is useful in determining the treatment response, degree of residual disease, and any signs of recurrence (3,11,12).
The management of SPTCL in the pediatric population is variable and largely depends on the histopathological diagnosis and institutional preferences. Potential treatment modalities include observation, immunosuppression, chemotherapy, and radiotherapy (4,13). Similar to the adults, pediatric case series have shown good treatment outcomes with dual immunosuppression (cyclosporin-A and prednisolone) in childhood SPTCL, particularly in the absence of HLH (4). One of the largest reviews of pediatric PTCL shows the best treatment outcome in SPTCL with maximum 5-years survival compared to the other pediatric PTCL (14).
Conclusion :
Clinically, the SPTCL often mimics the panniculitis from a benign dermatological disease; initial imaging and histopathological findings can also be non-diagnostic and a high index of suspicion is required to reach an accurate diagnosis. FDG-PET has emerged as an excellent imaging tool that can provide a road map for the diagnosis and management of the SPTCL by accurately guiding the biopsy site, eluding false-negative examinations, and by identifying the multicentricity of the disease. Our case represents the first case of breast SPTCL in the pediatric population and describes the role of FDG-PET in the evaluation of the lesion, determining the multicentricity of the disease, and loco-regional lymphadenopathy.
Conflict of Interest statement: No affiliations to any organization.
Acknowledgements : None
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